Bio


My research group studies complex molecular systems by using ultrafast multi-dimensional infrared and non-linear UV/Vis methods. A basic theme is to understand the role of mesoscopic structure on the properties of molecular systems. Many systems have structure on length scales large compare to molecules but small compared to macroscopic dimensions. The mesoscopic structures occur on distance scales of a few nanometers to a few tens of nanometers. The properties of systems, such as water in nanoscopic environments, room temperature ionic liquids, functionalized surfaces, liquid crystals, metal organic frameworks, water and other liquids in nanoporous silica, polyelectrolyte fuel cell membranes, vesicles, and micelles depend on molecular level dynamics and intermolecular interactions. Our ultrafast measurements provide direct observables for understanding the relationships among dynamics, structure, and intermolecular interactions.

Bulk properties are frequently a very poor guide to understanding the molecular level details that determine the nature of a chemical process and its dynamics. Because molecules are small, molecular motions are inherently very fast. Recent advances in methodology developed in our labs make it possible for us to observe important processes as they occur. These measurements act like stop-action photography. To focus on a particular aspect of a time evolving system, we employ sequences of ultrashort pulses of light as the basis for non-linear methods such as ultrafast infrared two dimensional vibrational echoes, optical Kerr effect methods, and ultrafast IR transient absorption experiments.

We are using ultrafast 2D IR vibrational echo spectroscopy and other multi-dimensional IR methods, which we have pioneered, to study dynamics of molecular complexes, water confined on nm lengths scales with a variety of topographies, molecules bound to surfaces, ionic liquids, and materials such as metal organic frameworks and porous silica. We can probe the dynamic structures these systems. The methods are somewhat akin to multidimensional NMR, but they probe molecular structural evolution in real time on the relevant fast time scales, eight to ten orders of magnitude faster than NMR. We are obtaining direct information on how nanoscopic confinement of water changes its properties, a topic of great importance in chemistry, biology, geology, and materials. For the first time, we are observing the motions of molecular bound to surfaces. In biological membranes, we are using the vibrational echo methods to study dynamics and the relationship among dynamics, structure, and function. We are also developing and applying theory to these problems frequently in collaboration with top theoreticians.

We are studying dynamics in complex liquids, in particular room temperature ionic liquids, liquid crystals, supercooled liquids, as well as in influence of small quantities of water on liquid dynamics. Using ultrafast optical heterodyne detected optical Kerr effect methods, we can follow processes from tens of femtoseconds to ten microseconds. Our ability to look over such a wide range of time scales is unprecedented. The change in molecular dynamics when a system undergoes a phase change is of fundamental and practical importance. We are developing detailed theory as the companion to the experiments.

We are studying photo-induced proton transfer in nanoscopic water environments such as polyelectrolyte fuel cell membranes, using ultrafast UV/Vis fluorescence and multidimensional IR measurements to understand the proton transfer and other processes and how they are influenced by nanoscopic confinement. We want to understand the role of the solvent and the systems topology on proton transfer dynamics.

Academic Appointments


Administrative Appointments


  • Professor of Chemistry, Stanford University (1984 - 2000)
  • Associate Professor of Chemistry, Stanford University (1980 - 1984)
  • Assistant Professor of Chemistry, Stanford University (1974 - 1980)
  • Professor of Physics, University of Grenoble (1982 - 1982)

Honors & Awards


  • Ahmed Zewail Award in Ultrafast Science and Technology, American Chemical Society (2014)
  • Arthur L. Schawlow Prize in Laser Science, American Physical Society (2012)
  • Ellis R. Lippincott Award, Optical Society of America (2009)
  • Fellow, Optical Society of America (2009)
  • Fellow, Royal Society of Chemistry (2008)
  • E. Bright Wilson Award for Spectroscopy, American Chemical Society (2007)
  • Member, National Academy of Sciences (2007)
  • Earl K. Plyler Prize for Molecular Spectroscopy, American Physical Society (2000)
  • Member, American Academy of Arts and Sciences (1999)
  • Dean's Award for Distinguished Teaching, Stanford University (1986)
  • Fellow, Guggenheim Foundation (1983)
  • Fellow, American Physical Society (1982)
  • Dreyfus Teacher-Scholar Award, Camille & Henry Dreyfus Foundation (1977)
  • Fellow, Alfred P. Sloan Foundation (1977)
  • Fellow, Camille & Henry Dreyfus Foundation (1977)
  • Phi Beta Kappa, University of California at Berkeley (1969)
  • Fellow, National Science Foundation (1966-1967)

Boards, Advisory Committees, Professional Organizations


  • Member, Editorial Board, Journal of Chemical Physics (1987 - 1990)
  • Member, Advisory Board, Journal of Physical Chemistry (1986 - 1989)
  • Associate Editor, Journal of Luminescence (1988 - Present)
  • Advisory Editor, Chemical Physics (1985 - Present)
  • Advisory Editor, Chemical Physics Letters (1984 - 2006)
  • Chairman, Awards Committee, Earl K. Plyler Prize for Molecular Spectroscopy (2006 - 2006)
  • Chairman, 7th International Conference on Unconventional Photoactive Systems, Stanford University (1995 - 1995)
  • Chairman, Fourth International Conference on Dynamical Processes, Stanford University (1983 - 1983)
  • Member, American Chemical Society
  • Member, American Optical Society
  • Member, American Physical Society
  • Member, Royal Society of Chemistry
  • Member, Sigma Xi

Professional Education


  • Ph.D., University of California at Berkeley, Chemistry (1974)
  • B.S., University of California at Berkeley, Chemistry (1969)

2019-20 Courses


Stanford Advisees


All Publications


  • Structural Influences on the Fast Dynamics of Alkylsiloxane Monolayers on SiO2 Surfaces Measured with 2D IR Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY C Yan, C., Yuan, R., Nishida, J., Fayer, M. D. 2015; 119 (29): 16811-16823
  • The Influence of Cholesterol on Fast Dynamics Inside of Vesicle and Planar Phospholipid Bilayers Measured with 2D IR Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Kel, O., Tamimi, A., Fayer, M. D. 2015; 119 (29): 8852-8862

    View details for DOI 10.1021/jp503940k

    View details for Web of Science ID 000358623900004

  • Dynamics of water, methanol, and ethanol in a room temperature ionic liquid. journal of chemical physics Kramer, P. L., Giammanco, C. H., Fayer, M. D. 2015; 142 (21): 212408-?

    Abstract

    The dynamics of a series of small molecule probes with increasing alkyl chain length: water, methanol, and ethanol, diluted to low concentration in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was investigated with 2D infrared vibrational echo (2D IR) spectroscopy and polarization resolved pump-probe (PP) experiments on the deuterated hydroxyl (O-D) stretching mode of each of the solutes. The long timescale spectral diffusion observed by 2D IR, capturing complete loss of vibrational frequency correlation through structural fluctuation of the medium, shows a clear but not dramatic slowing as the probe alkyl chain length is increased: 23 ps for water, 28 ps for methanol, and 34 ps for ethanol. Although in each case, only a single population of hydroxyl oscillators contributes to the infrared line shapes, the isotropic pump-probe decays (normally caused by population relaxation) are markedly nonexponential at short times. The early time features correspond to the timescales of the fast spectral diffusion measured with 2D IR. These fast isotropic pump-probe decays are produced by unequal pumping of the OD absorption band to a nonequilibrium frequency dependent population distribution caused by significant non-Condon effects. Orientational correlation functions for these three systems, obtained from pump-probe anisotropy decays, display several periods of restricted angular motion (wobbling-in-a-cone) followed by complete orientational randomization. The cone half-angles, which characterize the angular potential, become larger as the experimental frequency moves to the blue. These results indicate weakening of the angular potential with decreasing hydrogen bond strength. The slowest components of the orientational anisotropy decays are frequency-independent and correspond to the complete orientational randomization of the solute molecule. These components slow appreciably with increasing chain length: 25 ps for water, 42 ps for methanol, and 88 ps for ethanol. The shape and volume of the probe, therefore, impact reorientation far more severely than they do spectral diffusion at long times, though these two processes occur on similar timescales at earlier times.

    View details for DOI 10.1063/1.4914156

    View details for PubMedID 26049428

  • Proton Transfer in Ionic and Neutral Reverse Micelles JOURNAL OF PHYSICAL CHEMISTRY B Lawler, C., Fayer, M. D. 2015; 119 (19): 6024-6034

    Abstract

    Proton-transfer kinetics in both ionic and neutral reverse micelles were studied by time-correlated single-photon counting investigations of the fluorescent photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). Orientational dynamics of dissolved probe molecules in the water pools of the reverse micelles were also investigated by time-dependent fluorescence anisotropy measurements of MPTS, the methoxy derivative of HPTS. These experiments were compared to the same experiments in bulk water. It was found that in ionic reverse micelles (surfactant Aerosol OT, AOT), orientational motion (fluorescence anisotropy decay) of MPTS was relatively unhindered, consistent with MPTS being located in the water core of the reverse micelle away from the water-surfactant interface. In nonionic reverse micelles (surfactant Igepal CO-520, Igepal), however, orientational anisotropy displayed a slow multiexponential decay consistent with wobbling-in-a-cone behavior, indicating MPTS is located at the water-surfactant interface. HPTS proton transfer in ionic reverse micelles followed kinetics qualitatively like those in bulk water, albeit slower, with the long-time power law time dependence associated with recombination of the proton with the dissociated photoacid, suggesting a modified diffusion-controlled process. However, the power law exponents in the ionic reverse micelles are smaller (∼ -0.55) than that in bulk water (-1.1). In neutral reverse micelles, proton-transfer kinetics did not show discernible power law behavior and were best represented by a two-component model with one relatively waterlike population and a population with a faster fluorescence lifetime and negligible proton transfer. We explain the Igepal results on the basis of close association between the probe and the neutral water-surfactant interface, with the probe experiencing a distribution of more and less waterlike environments. In addition, the observation in bulk water of a power law t(-1.1) for diffusion-controlled recombination is in contrast to the theoretical prediction of t(-1.5) and previously reported observations. The difference from prior experimental results is discussed.

    View details for DOI 10.1021/acs.jpcb.5b02753

    View details for Web of Science ID 000354911300010

    View details for PubMedID 25913559

  • Structural dynamics inside a functionalized metal-organic framework probed by ultrafast 2D IR spectroscopy. Proceedings of the National Academy of Sciences of the United States of America Nishida, J., Tamimi, A., Fei, H., Pullen, S., Ott, S., Cohen, S. M., Fayer, M. D. 2014; 111 (52): 18442-18447

    Abstract

    The structural elasticity of metal-organic frameworks (MOFs) is a key property for their functionality. Here, we show that 2D IR spectroscopy with pulse-shaping techniques can probe the ultrafast structural fluctuations of MOFs. 2D IR data, obtained from a vibrational probe attached to the linkers of UiO-66 MOF in low concentration, revealed that the structural fluctuations have time constants of 7 and 670 ps with no solvent. Filling the MOF pores with dimethylformamide (DMF) slows the structural fluctuations by reducing the ability of the MOF to undergo deformations, and the dynamics of the DMF molecules are also greatly restricted. Methodology advances were required to remove the severe light scattering caused by the macroscopic-sized MOF particles, eliminate interfering oscillatory components from the 2D IR data, and address Förster vibrational excitation transfer.

    View details for DOI 10.1073/pnas.1422194112

    View details for PubMedID 25512539

    View details for PubMedCentralID PMC4284562

  • New divergent dynamics in the isotropic to nematic phase transition of liquid crystals measured with 2D IR vibrational echo spectroscopy JOURNAL OF CHEMICAL PHYSICS Sokolowsky, K. P., Bailey, H. E., Fayer, M. D. 2014; 141 (19)

    View details for DOI 10.1063/1.4901081

    View details for Web of Science ID 000345514700026

  • Orientational Dynamics in a Lyotropic Room Temperature Ionic Liquid JOURNAL OF PHYSICAL CHEMISTRY B Sturlaugson, A. L., Arima, A. Y., Bailey, H. E., Fayer, M. D. 2013; 117 (47): 14775-14784

    View details for DOI 10.1021/jp407325b

    View details for Web of Science ID 000330160100020

    View details for PubMedID 24171452

  • Dynamics of isolated water molecules in a sea of ions in a room temperature ionic liquid. journal of physical chemistry. B Wong, D. B., Giammanco, C. H., Fenn, E. E., Fayer, M. D. 2013; 117 (2): 623-635

    Abstract

    The vibrational dynamics of the antisymmetric and symmetric stretching modes of very low concentration spatially isolated D(2)O molecules in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF(6)) were examined using two-dimensional infrared (2D IR) vibrational echo spectroscopy and infrared pump-probe experiments. In BmImPF(6), D(2)O's antisymmetric and symmetric stretching modes are well resolved in the IR absorption spectrum in spite of the fact that the D(2)O is surrounded by a sea of ions, making it is possible to study inter- and intramolecular dynamics. Both population exchange between the modes and excited-state relaxation to the ground state contribute to the population dynamics. The kinetics for the incoherent population exchange (scattering) between the two modes was determined by the time dependence of the exchange peaks in the 2D IR spectrum. In addition, coherent quantum beats were observed at short time in both the amplitudes and 2D IR band shapes of the modes. The quantum beat decay is caused by dephasing due to both inhomogeneous and homogeneous broadening of the spectral lines. Analysis of the oscillations of the 2D line shapes demonstrates that there is some degree of anticorrelation in the inhomogeneous broadening of the two modes. It is proposed that a distribution in the coupling strength between the local modes that give rise to symmetric and antisymmetric eigenstates is responsible for the anticorrelation. Spectral diffusion, caused by structural evolution of the medium, occurs on multiple time scales and is identical for the two modes within experimental error. The spectral diffusion is fast compared to the time scale for complete orientational randomization of the RTIL. Spectral diffusion of the OD stretch of HOD in BmImPF(6) was also measured, and is essentially the same as that of the D(2)O modes. Orientational anisotropy measurements of HOD in BmImPF(6) determined the orientational relaxation dynamics of the isolated HOD molecules.

    View details for DOI 10.1021/jp310086s

    View details for PubMedID 23276306

  • Protein Dynamics Studied with Ultrafast Two-Dimensional Infrared Vibrational Echo Spectroscopy ACCOUNTS OF CHEMICAL RESEARCH Thielges, M. C., Fayer, M. D. 2012; 45 (11): 1866-1874

    Abstract

    Proteins, enzymes, and other biological molecules undergo structural dynamics as an intrinsic part of their biological functions. While many biological processes occur on the millisecond, second, and even longer time scales, the fundamental structural dynamics that eventually give rise to such processes occur on much faster time scales. Many decades ago, chemical kineticists focused on the inverse of the reaction rate constant as the important time scale for a chemical reaction. However, through transition state theory and a vast amount of experimental evidence, we now know that the key events in a chemical reaction can involve structural fluctuations that take a system of reactants to its transition state, the crossing of a barrier, and the eventual relaxation to product states. Such dynamics occur on very fast time scales. Today researchers would like to investigate the fast structural fluctuations of biological molecules to gain an understanding of how biological processes proceed from simple structural changes in biomolecules to the final, complex biological function. The study of the fast structural dynamics of biological molecules requires experiments that operate on the appropriate time scales, and in this Account, we discuss the application of ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy to the study of protein dynamics. The 2D IR vibrational echo experiment is akin to 2D NMR, but it operates on time scales many orders of magnitude faster. In the experiments, a particular vibrational oscillator serves as a vibrational dynamics probe. As the structure of the protein evolves in time, the structural changes are manifested as time-dependent changes in the frequency of the vibrational dynamics probe. The 2D IR vibrational echo experiments can track the vibrational frequency evolution, which we then relate to the time evolution of the protein structure. In particular, we measured protein substate interconversion for mutants of myoglobin using 2D IR chemical exchange spectroscopy and observed well-defined substate interconversion on a sub-100 ps time scale. In another study, we investigated the influence of binding five different substrates to the enzyme cytochrome P450(cam). The various substrates affect the enzyme dynamics differently, and the observed dynamics are correlated with the enzyme's selectivity of hydroxylation of the substrates and with the substrate binding affinity.

    View details for DOI 10.1021/ar200275k

    View details for PubMedID 22433178

    View details for PubMedCentralID PMC3389584

  • Analysis of Water in Confined Geometries and at Interfaces ANNUAL REVIEW OF ANALYTICAL CHEMISTRY, VOL 3 Fayer, M. D., Levinger, N. E. 2010; 3: 89-107

    Abstract

    The properties of water depend on its extended hydrogen bond network and the continual picosecond-time scale structural evolution of the network. Water molecules in confined environments with pools a few nanometers in diameter or at interfaces undergo hydrogen bond structural dynamics that differ drastically from the dynamics they undergo in bulk water. Orientational motions of water require hydrogen bond network rearrangement. Therefore, observations of orientational relaxation in nanoscopic water systems provide information about the influence of confinement and interfaces on hydrogen bond dynamics. Ultrafast infrared polarization- and wavelength-selective pump-probe experiments can measure the orientational relaxation of water and distinguish water at an interface from water removed from an interface. These experiments can be applied to water in reverse micelles (spherical nanopools). The results provide quantitative determination of the dynamics of water as a function of the size and nature of the confining structure.

    View details for DOI 10.1146/annurev-anchem-070109-103410

    View details for Web of Science ID 000280599500005

    View details for PubMedID 20636035

  • Ultrafast dynamics of solute-solvent complexation observed at thermal equilibrium in real time SCIENCE Zheng, J. R., Kwak, K., Asbury, J., Chen, X., Piletic, I. R., Fayer, M. D. 2005; 309 (5739): 1338-1343

    Abstract

    In general, the formation and dissociation of solute-solvent complexes have been too rapid to measure without disturbing the thermal equilibrium. We were able to do so with the use of two-dimensional infrared vibrational echo spectroscopy, an ultrafast vibrational analog of two-dimensional nuclear magnetic resonance spectroscopy. The equilibrium dynamics of phenol complexation to benzene in a benzene-carbon tetrachloride solvent mixture were measured in real time by the appearance of off-diagonal peaks in the two-dimensional vibrational echo spectrum of the phenol hydroxyl stretch. The dissociation time constant tau(d) for the phenol-benzene complex was 8 picoseconds. Adding two electron-donating methyl groups to the benzene nearly tripled the value of tau(d) and stabilized the complex, whereas bromobenzene, with an electron-withdrawing bromo group, formed a slightly weaker complex with a slightly lower tau(d). The spectroscopic method holds promise for studying a wide variety of other fast chemical exchange processes.

    View details for DOI 10.1126/science.1116213

    View details for Web of Science ID 000231543300034

    View details for PubMedID 16081697

  • Imidazole and 1-Methylimidazole Hydrogen Bonding and Nonhydrogen Bonding Liquid Dynamics: Ultrafast IR Experiments. The journal of physical chemistry. B Shin, J. Y., Wang, Y., Yamada, S. A., Hung, S. T., Fayer, M. D. 2019

    Abstract

    The dynamics of imidazole (IM) and 1-methylimidazole (1-MeIM) in the liquid phase at 95 °C were studied by IR polarization selective pump-probe and two-dimensional IR (2D IR) spectroscopies. The two molecules are very similar structurally except that IM can be simultaneously a hydrogen bond donor and acceptor and therefore forms extended hydrogen-bonded networks. The broader IR absorption spectrum and a shorter vibrational lifetime of the vibrational probe, selenocyanate anion (SeCN-), in IM vs 1-MeIM indicate that stronger hydrogen bonding exists between SeCN- and IM. Molecular dynamics (MD) simulations support the strong hydrogen bond formation between SeCN- and IM via the HN moiety. SeCN- makes two H-bonds with IM; it is inserted in the IM H-bonded chains rather than being a chain terminator. The strong hydrogen bonding influenced the reorientation dynamics of SeCN- in IM, leading to a more restricted short time angular sampling (wobbling-in-a-cone). The complete orientational diffusion time in IM is 1.7 times slower than in 1-MeIM, but the slow down is less than expected, considering the 3-fold larger viscosity of IM. The jump reorientation mechanism accounts for the anomalously fast orientational relaxation in IM, and the MD simulations determined the average jump angle of the probe between hydrogen bonding sites. Spectral diffusion time constants obtained from the 2D IR experiments are only modestly slower in IM than in 1-MeIM in spite of the significant increase in viscosity. The results indicate that the spectral diffusion sensed by the SeCN- has IM hydrogen bond dynamics contributions not present in 1-MeIM.

    View details for PubMedID 30727725

  • Orientational Pair Correlations in a Dipolar Molecular Liquid: Time-Resolved Resonant and Nonresonant Pump-Probe Spectroscopies. The journal of physical chemistry. B Yamada, S. A., Bailey, H. E., Fayer, M. D. 2018

    Abstract

    Orientational pair correlations (OPCs), when they are sufficiently strong in a liquid, contain information on the interplay between structure and dynamics that arise from intermolecular interactions. Consequently, the quantification of OPCs remains a subject of substantial interest in current experimental and theoretical works. In the case of benzonitrile, the importance of OPCs remains ambiguous, owing to the use of model-dependent analyses or reliance on a single spectroscopic technique. Here, IR polarization-selective pump-probe (PSPP) and optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments were used to quantify OPCs in benzonitrile. These methods measure single molecule and collective orientational relaxation dynamics, respectively. A comparison of the orientational correlation function (PSPP) of the naturally abundant 13CN stretching mode and the polarizability anisotropy relaxation (OHD-OKE) of the liquid revealed that the collective reorientation time was a factor of 1.56 ± 0.08 slower than the single molecule reorientation time. The two types of measurements on dilute benzonitrile in carbon tetrachloride were the same within experimental error. These results support the proposition that OPCs exist and arise from the formation of parallel-aligned intermolecular structures in the neat liquid.

    View details for PubMedID 30411625

  • Ion-Molecule Complex Dissociation and Formation Dynamics in LiCl Aqueous Solutions from 2D IR Spectroscopy. The journal of physical chemistry. B Yuan, R., Yan, C., Fayer, M. 2018

    Abstract

    Ion-molecule complex dynamics as well as water dynamics in concentrated lithium chloride (LiCl) solutions are examined using ultrafast two-dimensional infrared (2D IR) spectroscopy with the CN stretching mode of methyl thiocyanate (MeSCN) as the vibrational probe. In pure water, MeSCN has a narrow symmetric absorption line shape. 2D IR spectral diffusion measurements of the CN stretch give the identical time dependence of water dynamics, as previously observed using the OD stretch of HOD in H2O. In concentrated LiCl solutions, the IR absorption spectrum of MeSCN displays two distinct peaks, one corresponding to water H-bonded to the N lone pair of MeSCN (W) and the other corresponding to Li+ associated with the N (L). These two species are in equilibrium, and switching of the CN bonding partner from Li+ to H2O and vice versa was observed and explicated with 2D IR chemical exchange spectroscopy. The MeSCN·Li+ complex dissociation time constant, tauLW, and the MeSCN·H2O dissociation time constant, tauWL, were determined. The observed tauLW chemical exchange dissociation time constant changes from 60 to 40 ps as the LiCl concentration decreases from 10.7 to 7.7 M, mainly due to the increase of the water concentration as the LiCl concentration is reduced. The observed time constants are independent of the model for the chemical reaction. With the assumption of a simple chemical equation, MeSCN·Li+ + H2O ⇄ MeSCN·H2O + Li+, the equilibrium equation rate constants were obtained from the observed chemical exchange time constants. It was determined that the equilibrium rate constants barely change even though the viscosity changes by a factor of 2 and the ionic strength changes by a factor of 1.4. Extrapolation to dilute LiCl solution estimates the tauLW to be 30 ps. The orientational relaxation (anisotropy decay) of both the W and L complexes was measured using polarization selective 2D IR experiments. The lithium-bonded species undergoes orientational relaxation 3 times slower than the water-bonded species in each LiCl solution studied. The difference demonstrates the distinct interactions with the medium experienced by the neutral and charged species in the concentrated salt solutions.

    View details for PubMedID 30365321

  • Dynamics and Microstructures of Nicotine/Water Binary Mixtures near the Lower Critical Solution Temperature. The journal of physical chemistry. B Bailey, H. E., Wang, Y., Lynch, S. R., Fayer, M. D. 2018

    Abstract

    The orientational dynamics and microscopic structures of nicotine/water binary mixtures near the system's lower critical solution temperature (LCST) were elucidated using optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy, nuclear magnetic resonance correlation spectroscopy (NMR COSY), first-principles calculations, and molecular dynamics simulations. Water concentrations were investigated from zero to close to pure water. At temperatures below the LCST, OHD-OKE experiments measured an anomalous slowing as the phase transition concentration was approached. At moderate concentrations and low temperatures, intermolecular cross-peaks between nicotine and water molecules were observed in the COSY spectra, demonstrating the formation of structures that persist for milliseconds. These results suggest that pair correlations contribute to the slowdown in the OHD-OKE data at moderate water concentrations. First-principles calculations revealed that intermolecular hydrogen bonding coordination between nitrogen atoms in pyridine moieties and water lowers the energy barriers for the reorientations of the two nicotine rings. Atomistic simulations demonstrate that with increasing water concentration, hydrogen bonding interactions between pyridine moieties and water molecules first increase and then decrease with a maximum at moderate water concentrations. These experimental and computational characterizations of the dynamics of nicotine molecules are attributed to the distinct configurations of water molecules around the pyridine ring moieties in nicotine molecules.

    View details for PubMedID 30229656

  • Extraordinary Slowing of Structural Dynamics in Thin Films of a Room Temperature Ionic Liquid. ACS central science Nishida, J., Breen, J. P., Wu, B., Fayer, M. D. 2018; 4 (8): 1065–73

    Abstract

    The role that interfaces play in the dynamics of liquids is a fundamental scientific problem with vast importance in technological applications. From material science to biology, e.g., batteries to cell membranes, liquid properties at interfaces are frequently determinant in the nature of chemical processes. For most liquids, like water, the influence of an interface falls off on a 1 nm distance scale. Room temperature ionic liquids (RTILs) are a vast class of unusual liquids composed of complex cations and anions that are liquid salts at room temperature. They are unusual liquids with properties that can be finely tuned by selecting the structure of the cation and anion. RTILs are being used or developed in applications such as batteries, CO2 capture, and liquids for biological processes. Here, it is demonstrated quantitatively that the influence of an interface on RTIL properties is profoundly different from that observed in other classes of liquids. The dynamics of planar thin films of the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf2), were investigated using two-dimensional infrared spectroscopy (2D IR) with the CN stretch of SeCN- as the vibrational probe. The structural dynamics (spectral diffusion) of the thin films with controlled nanometer thicknesses were measured and compared to the dynamics of the bulk liquid. The samples were prepared by spin coating the RTIL, together with the vibrational probe, onto a surface functionalized with an ionic monolayer that mimics the structure of the BmimNTf2. Near-Brewster's angle reflection pump-probe geometry 2D IR facilitated the detection of the exceedingly small signals from the films, some of which were only 14 nm thick. Even in quarter micron (250 nm) thick films, the observed dynamics were much slower than those of the bulk liquid. Using a new theoretical description, the correlation length (exponential falloff of the influence of the interfaces) was found to be 28 ± 5 nm. This very long correlation length, 30 times greater than that of water, has major implications for the use of RTILs in devices and other applications.

    View details for PubMedID 30159404

  • Dynamically Disordered Lattice in a Layered Pb-I-SCN Perovskite Thin Film Probed by Two-Dimensional Infrared Spectroscopy. Journal of the American Chemical Society Nishida, J., Breen, J. P., Lindquist, K. P., Umeyama, D., Karunadasa, H. I., Fayer, M. D. 2018

    Abstract

    The dynamically flexible lattices in lead halide perovskites may play important roles in extending carrier recombination lifetime in 3D perovskite solar-cell absorbers and in exciton self-trapping in 2D perovskite white-light phosphors. Two-dimensional infrared (2D IR) spectroscopy was applied to study a recently reported Pb-I-SCN layered perovskite. The Pb-I-SCN perovskite was spin-coated on a SiO2 surface as a thin film, with a thickness of 100 nm, where the S12CN- anions were isotopically diluted with the ratio of S12CN:S13CN = 5:95 to avoid vibrational coupling and excitation transfer between adjacent SCN- anions. The 12CN stretch mode of the minor S12CN- component was the principal vibrational probe that reported on the structural evolution through 2D IR spectroscopy. Spectral diffusion was observed with a time constant of 4.1 ± 0.3 ps. Spectral diffusion arises from small structural changes that result in sampling of frequencies within the distribution of frequencies comprising the inhomogeneously broadened infrared absorption band. These transitions among discrete local structures are distinct from oscillatory phonon motions of the lattice. To accurately evaluate the structural dynamics through measurement of spectral diffusion, the vibrational coupling between adjacent SCN- anions had to be carefully treated. Although the inorganic layers of typical 2D perovskites are structurally isolated from each other, the 2D IR data demonstrated that the layers of the Pb-I-SCN perovskite are vibrationally coupled. When both S12CN- and S13CN- were pumped simultaneously, cross-peaks between S12CN and S13CN vibrations and an oscillating 2D band shape of the S12CN- vibration were observed. Both observables demonstrate vibrational coupling between the closest SCN- anions, which reside in different inorganic layers. The thin films and the isotopic dilution produced exceedingly small vibrational echo signal fields; measurements were made possible using the near-Brewster's angle reflection pump-probe geometry.

    View details for PubMedID 30024160

  • The influence of hydrophilicity on the orientational dynamics and structures of imidazolium-based ionic liquid/water binary mixtures. The Journal of chemical physics Bailey, H. E., Wang, Y., Fayer, M. D. 2018; 149 (4): 044501

    Abstract

    The orientational dynamics and microscopic structures of imidazolium-based ionic liquids of varying hydrophilicity were investigated using optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy and atomistic simulations. Hydrophilicity was tuned via anion selection, cation alkyl chain length, and the addition of a strong hydrogen bond donor on the cation (protic ionic liquid). In the hydrophobic samples, which saturate at relatively low water concentration, OHD-OKE data display Debye Stokes Einstein (DSE) behavior as a function of water concentration. The DSE behavior indicates that the microstructures of the hydrophobic ionic liquid/water mixtures do not fundamentally change as a function of water concentration. The hydrophilic samples have two regimes of different DSE behaviors demonstrating the presence of two structural regimes depending on water concentration. These experimental results indicate that in hydrophilic ionic liquid/water samples, significant structural changes occur to accommodate high water concentrations, while hydrophobic samples become water saturated because the restructuring of local ionic structures is unfavorable. Atomistic simulations show that the local ionic microstructures experience distinct changes in these hydrophilic ionic liquid/water binary samples because of the delicate interplay of intermolecular interactions among imidazolium cations, hydrophilic anions, and water molecules.

    View details for PubMedID 30068204

  • Water Dynamics in Polyacrylamide Hydrogels. Journal of the American Chemical Society Yan, C., Kramer, P. L., Yuan, R., Fayer, M. D. 2018

    Abstract

    Polymeric hydrogels have wide applications including electrophoresis, biocompatible materials, water superadsorbents, and contact lenses. The properties of hydrogels involve the poorly characterized molecular dynamics of water and solutes trapped within the three-dimensional cross-linked polymer networks. Here we apply ultrafast two-dimensional infrared (2D IR) vibrational echo and polarization-selective pump-probe (PSPP) spectroscopies to investigate the ultrafast molecular dynamics of water and a small molecular anion solute, selenocyanate (SeCN-), in polyacrylamide hydrogels. For all mass concentrations of polymer studied (5% and above), the hydrogen-bonding network reorganization (spectral diffusion) dynamics and reorientation dynamics reported by both water and SeCN- solvated by water are significantly slower than in bulk water. As the polymer mass concentration increases, molecular dynamics in the hydrogels slow further. The magnitudes of the slowing, measured with both water and SeCN-, are similar. However, the entire hydrogen-bonding network of water molecules appears to slow down as a single ensemble, without a difference between the core water population and the interface water population at the polymer-water surface. In contrast, the dissolved SeCN- do exhibit two-component dynamics, where the major component is assigned to the anions fully solvated in the confined water nanopools. The slower component has a small amplitude which is correlated with the polymer mass concentration and is assigned to adsorbed anions strongly interacting with the polymer fiber networks.

    View details for PubMedID 29985609

  • Preface: Special Topic on Chemical Physics of Ionic Liquids JOURNAL OF CHEMICAL PHYSICS Perkin, S., Kirchner, B., Fayer, M. D. 2018; 148 (19)

    View details for DOI 10.1063/1.5039492

    View details for Web of Science ID 000432853800003

  • Influence of mesoscopic confinement on the dynamics of room temperature ionic liquids Fayer, M. AMER CHEMICAL SOC. 2018
  • Monolayer dynamics at the air/ water interface: From ultrafast to ultraslow dynamics Fayer, M. AMER CHEMICAL SOC. 2018
  • Ultrafast to Ultraslow Dynamics of a Langmuir Monolayer at the Air/Water Interface Observed with Reflection Enhanced 2D IR Spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Yan, C., Thomaz, J. E., Wang, Y., Nishida, J., Yuan, R., Breen, J. P., Fayer, M. D. 2017; 139 (46): 16518–27

    Abstract

    Monolayers play important roles in naturally occurring phenomena and technological processes. Monolayers at the air/water interface have received considerable attention, yet it has proven difficult to measure monolayer and interfacial molecular dynamics. Here we employ a new technique, reflection enhanced two-dimensional infrared (2D IR) spectroscopy, on a carbonyl stretching mode of tricarbonylchloro-9-octadecylamino-4,5-diazafluorenerhenium(I) (TReF18) monolayers at two surface densities. Comparison to experiments on a water-soluble version of the metal carbonyl headgroup shows that water hydrogen bond rearrangement dynamics slow from 1.5 ps in bulk water to 3.1 ps for interfacial water. Longer time scale fluctuations were also observed and attributed to fluctuations of the number of hydrogen bonds formed between water and the three carbonyls of TReF18. At the higher surface density, two types of TReF18 minor structures are observed in addition to the main structure. The reflection method can take usable 2D IR spectra on the monolayer within 8 s, enabling us to track the fluctuating minor structures' appearance and disappearance on a tens of seconds time scale. 2D IR chemical exchange spectroscopy further shows these structures interconvert in 30 ps. Finally, 2D spectral line shape evolution reveals that it takes the monolayers hours to reach macroscopic structural equilibrium.

    View details for PubMedID 29072913

  • The influence of mesoscopic confinement on the dynamics of imidazolium-based room temperature ionic liquids in polyether sulfone membranes JOURNAL OF CHEMICAL PHYSICS Thomaz, J. E., Bailey, H. E., Fayer, M. D. 2017; 147 (19): 194502

    Abstract

    The structural dynamics of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (CnmimNTf2, n = 2, 4, 6, 10: ethyl-Emim; butyl-Bmim; hexyl-Hmim; decyl-Dmim) room temperature ionic liquids confined in the pores of polyether sulfone (PES 200) membranes with an average pore size of ∼350 nm and in the bulk liquids were studied. Time correlated single photon counting measurements of the fluorescence of the fluorophore coumarin 153 (C153) were used to observe the time-dependent Stokes shift (solvation dynamics). The solvation dynamics of C153 in the ionic liquids are multiexponential decays. The multiexponential functional form of the decays was confirmed as the slowest decay component of each bulk liquid matches the slowest component of the liquid dynamics measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments, which is single exponential. The fact that the slowest component of the Stokes shift matches the OHD-OKE data in all four liquids identifies this component of the solvation dynamics as arising from the complete structural randomization of the liquids. Although the pores in the PES membranes are large, confinement on the mesoscopic length scale results in substantial slowing of the dynamics, a factor of ∼4, for EmimNTf2, with the effect decreasing as the chain length increases. By DmimNTf2, the dynamics are virtually indistinguishable from those in the bulk liquid. The rotation relaxation of C153 in the four bulk liquids was also measured and showed strong coupling between the C153 probe and its environment.

    View details for PubMedID 29166092

  • Discontinuity in Fast Dynamics at the Glass Transition of ortho-Terphenyl JOURNAL OF PHYSICAL CHEMISTRY B Hoffman, D. J., Fayer, M. D. 2017; 121 (45): 10417–28

    Abstract

    The dynamics of the molecular glass former ortho-terphenyl through the glass transition were observed with two-dimensional infrared vibrational spectroscopy measurements of spectral diffusion using the small probe molecule phenylselenocyanate. Although the slow diffusive motions were not visible on the experimental time scale, a picosecond-scale exponential relaxation was observed at temperatures from above to well below the glass transition temperature. The characteristic time scale has a smooth temperature dependence from the liquid into the glass phase, but the range of vibrational frequencies the probe samples displayed a discontinuity at the glass transition temperature. Complementary pump-probe experiments associate the observed motion with density fluctuations. The key features of the dynamics are reproduced with a simple corrugated well potential energy surface model. In addition, the temperature dependence of the homogeneous vibrational dephasing was found to have a T2 functional form, where T is the absolute temperature.

    View details for PubMedID 29039665

  • Proton Transfer in Perfluorosulfonic Acid Fuel Cell Membranes with Differing Pendant Chains and Equivalent Weights JOURNAL OF PHYSICAL CHEMISTRY B Thomaz, J. E., Lawler, C. M., Fayer, M. D. 2017; 121 (17): 4544-4553

    Abstract

    Proton transfer in the nanoscopic water channels of polyelectrolyte fuel cell membranes was studied using a photoacid, 8-hydroxypyrene-1,3,6-trisulfonic acid sodium salt (HPTS), in the channels. The local environment of the probe was determined using 8-methoxypyrene-1,3,6-trisulfonic acid sodium salt (MPTS), which is not a photoacid. Three fully hydrated membranes, Nafion (DuPont) and two 3M membranes, were studied to determine the impact of different pendant chains and equivalent weights on proton transfer. Fluorescence anisotropy and excited state population decay data that characterize the local environment of the fluorescent probes and proton transfer dynamics were measured. The MPTS lifetime and anisotropy results show that most of the fluorescent probes have a bulk-like water environment with a relatively small fraction interacting with the channel wall. Measurements of the HPTS protonated and deprotonated fluorescent bands' population decays provided information on the proton transport dynamics. The decay of the protonated band from ∼0.5 ns to tens of nanoseconds is in part determined by dissociation and recombination with the HPTS, providing information on the ability of protons to move in the channels. The dissociation and recombination is manifested as a power law component in the protonated band fluorescence decay. The results show that equivalent weight differences between two 3M membranes resulted in a small difference in proton transfer. However, differences in pendant chain structure did significantly influence the proton transfer ability, with the 3M membranes displaying more facile transfer than Nafion.

    View details for DOI 10.1021/acs.jpcb.7b01764

    View details for Web of Science ID 000400881300024

    View details for PubMedID 28398064

  • Dynamics in a Water Interfacial Boundary Layer Investigated with IR Polarization-Selective Pump-Probe Experiments JOURNAL OF PHYSICAL CHEMISTRY B Yuan, R., Yan, C., Nishida, J., Fayer, M. D. 2017; 121 (17): 4530-4537

    Abstract

    The dynamics of water molecules near the surfactant interface in large Aerosol-OT reverse micelles (RMs) (w0 = 16-25) was investigated with IR polarization-selective pump-probe experiments using the SeCN(-) anion as a vibrational probe. Linear absorption spectra of RMs (w0 = 25-2) can be decomposed into the weighted sum of the SeCN(-) spectra in bulk water and the spectrum of the SeCN(-) anion interacting with the interfacial sulfonate head groups (w0 = 1). The spectra of the large RMs, w0 ≥ 16, are overwhelmingly dominated by the bulk water component. Anisotropy decays (orientational relaxation) of the anion for w0 ≥ 16 displayed bulk water relaxation (1.4 and 4.5 ps) plus an additional slow decay with a time constant of ∼13 ps. The amplitude of the slow decay was too large to be associated with SeCN(-) in contact with the interface on the basis of the linear spectrum decomposition. The results indicate that the observed slow components arise from SeCN(-) in a water boundary layer, in which water molecules are perturbed by the interface but are not directly associated with it. This layer is the transition between water in direct contact with the interface and bulk water in the large RM cores. In the boundary layer, the water dynamics is slow compared to that in bulk water.

    View details for DOI 10.1021/acs.jpcb.7b01028

    View details for Web of Science ID 000400881300022

    View details for PubMedID 28379003

  • Direct observation of dynamic crossover in fragile molecular glass formers with 2D IR vibrational echo spectroscopy JOURNAL OF CHEMICAL PHYSICS Hoffman, D. J., Sokolowsky, K. P., Fayer, M. D. 2017; 146 (12)

    Abstract

    The dynamics of supercooled liquids of the molecular glass formers benzophenone and ortho-terphenyl were investigated with 2D IR spectroscopy using long-lived vibrational probes. The long lifetimes of the probes enabled structural dynamics of the liquids to be studied from a few hundred femtoseconds to a nanosecond. 2D IR experiments measured spectraldiffusion of a vibrational probe, which reports on structural fluctuations of the liquid. Analysis of the 2D IR data provides the frequency-frequency correlation function (FFCF). Two vibrational probes were examined with equivalent results, demonstrating the observed liquid dynamics are not significantly influenced by the probe molecules. At higher temperatures, the FFCF is a biexponential decay. However, at mild supercooling, the biexponential decay is no longer sufficient, indicating a dynamic crossover. The crossover occurs at a temperature well above the mode-coupling theory critical temperature for the given liquid, indicating dynamic heterogeneity above the critical temperature. Examination of the low temperature data with lifetime density analysis shows that the change is best described as an additional, distinct relaxation that shows behavior consistent with a slow β-process.

    View details for DOI 10.1063/1.4978852

    View details for Web of Science ID 000397929300058

    View details for PubMedID 28388155

  • Enhanced nonlinear spectroscopy for monolayers and thin films in near-Brewster's angle reflection pump-probe geometry JOURNAL OF CHEMICAL PHYSICS Nishida, J., Yan, C., Fayer, M. D. 2017; 146 (9)

    View details for DOI 10.1063/1.4977508

    View details for Web of Science ID 000397312800042

  • Dynamics in a Room-Temperature Ionic Liquid from the Cation Perspective: 2D IR Vibrational Echo Spectroscopy. Journal of the American Chemical Society Yamada, S. A., Bailey, H. E., Tamimi, A., Li, C., Fayer, M. D. 2017; 139 (6): 2408-2420

    Abstract

    The dynamics of the room-temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf2) were investigated with two-dimensional infrared (2D IR) vibrational echo spectroscopy and polarization selective pump-probe (PSPP) experiments. The CN stretch frequency of a modified Bmim(+) cation (2-SeCN-Bmim(+)), in which a SeCN moiety was substituted onto the C-2 position of the imidazolium ring, was used as a vibrational probe. A major result of the 2D IR experiments is the observation of a long time scale structural spectral diffusion component of 600 ps in addition to short and intermediate time scales similar to those measured for selenocyanate anion (SeCN(-)) dissolved in BmimNTf2. In contrast to 2-SeCN-Bmim(+), SeCN(-) samples its inhomogeneous line width nearly an order of magnitude faster than the complete structural randomization time of neat BmimNTf2 liquid (870 ± 20 ps) measured with optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments. The orientational correlation function obtained from PSPP experiments on 2-SeCN-Bmim(+) exhibits two periods of restricted angular diffusion (wobbling-in-a-cone) followed by complete orientational randomization on a time scale of 900 ± 20 ps, significantly slower than observed for SeCN(-) but identical within experimental error to the complete structural randomization time of BmimNTf2. The experiments indicate that 2-SeCN-Bmim(+) is sensitive to local motions of the ionic region that influence the spectral diffusion and reorientation of small, anionic, and neutral molecules as well as significantly slower, longer-range fluctuations that are responsible for complete randomization of the liquid structure.

    View details for DOI 10.1021/jacs.6b12011

    View details for PubMedID 28099808

  • Dynamics of a Room Temperature Ionic Liquid in Supported Ionic Liquid Membranes vs the Bulk Liquid: 2D IR and Polarized IR Pump-Probe Experiments JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Shin, J. Y., Yamada, S. A., Fayer, M. D. 2017; 139 (1): 311-323

    Abstract

    Supported ionic liquid membranes (SILMs) are membranes that have ionic liquids impregnated in their pores. SILMs have been proposed for advanced carbon capture materials. Two-dimensional infrared (2D IR) and polarization selective IR pump-probe (PSPP) techniques were used to investigate the dynamics of reorientation and spectral diffusion of the linear triatomic anion, SeCN(-), in poly(ether sulfone) (PES) membranes and room-temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2). The dynamics in the bulk EmimNTf2 were compared to its dynamics in the SILM samples. Two PES membranes, PES200 and PES30, have pores with average sizes, ∼300 nm and ∼100 nm, respectively. Despite the relatively large pore sizes, the measurements reveal that the reorientation of SeCN(-) and the RTIL structural fluctuations are substantially slower in the SILMs than in the bulk liquid. The complete orientational randomization, slows from 136 ps in the bulk to 513 ps in the PES30. 2D IR measurements yield three time scales for structural spectral diffusion (SSD), that is, the time evolution of the liquid structure. The slowest decay constant increases from 140 ps in the bulk to 504 ps in the PES200 and increases further to 1660 ps in the PES30. The results suggest that changes at the interface propagate out and influence the RTIL structural dynamics even more than a hundred nanometers from the polymer surface. The differences between the IL dynamics in the bulk and in the membranes suggest that studies of bulk RTIL properties may be poor guides to their use in SILMs in carbon capture applications.

    View details for DOI 10.1021/jacs.6b10695

    View details for Web of Science ID 000392036900049

    View details for PubMedID 27973786

  • Water Dynamics in 1-Alkyl-3-methylimidazolium Tetrafluoroborate Ionic Liquids JOURNAL OF PHYSICAL CHEMISTRY B Giammanco, C. H., Kramer, P. L., Wong, D. B., Fayer, M. D. 2016; 120 (44): 11523-11538

    Abstract

    The effects of water concentration and varying alkyl chain length on the dynamics of water in 1-alkyl-3-methylimidazolium tetrafluoroborate room-temperature ionic liquids (RTILs) were characterized using two-dimensional infrared (2D IR) vibrational echo spectroscopy and polarization-selective IR pump-probe experiments to study the water hydroxyl (OD) stretching mode of dilute HOD in H2O. Three imidazolium cation alkyl chain lengths, ethyl (Emim(+)), butyl (Bmim(+)), and decyl (Dmim(+)), were investigated. Both Bmim(+) and Dmim(+) cations have sufficiently long chains that the liquids exhibit polar-apolar segregation, whereas the Emim(+) IL has no significant apolar aggregation. Although the OD absorption spectra are independent of the chain length, the measured reorientation and spectral diffusion dynamics are chain length dependent and tend to slow when the alkyl chain is long enough for polar-apolar segregation. As the water concentration is increased, a water-associated water population forms, absorbing in a new spectral region red-shifted from the isolated, anion-associated, water population. Furthermore, the anion-associated water dynamics are accelerated. At sufficiently high water concentrations, water in all of the RTILs experiences similar dynamics, the solvent structures having been fluidized by the addition of water. The water concentration at which the dilute water dynamics changes to fluidized dynamics depends on the alkyl chain length, which determines the extent and ordering of the apolar regions. Increases in both water concentration and alkyl chain length serve to modify the ordering of the RTIL, but with opposite and competing effects on the dissolved water dynamics.

    View details for DOI 10.1021/acs.jpcb.6b08410

    View details for Web of Science ID 000387738300019

    View details for PubMedID 27726398

  • Orientational Dynamics of a Functionalized Alkyl Planar Monolayer Probed by Polarization-Selective Angle-Resolved Infrared Pump-Probe Spectroscopy. Journal of the American Chemical Society Nishida, J., Yan, C., Fayer, M. D. 2016: -?

    Abstract

    Polarization-selective angle-resolved infrared pump-probe spectroscopy was developed and used to study the orientational dynamics of a planar alkylsiloxane monolayer functionalized with a rhenium metal carbonyl headgroup on an SiO2 surface. The technique, together with a time-averaged infrared linear dichroism measurement, characterized picosecond orientational relaxation of the headgroup occurring at the monolayer-air interface by employing several sets of incident angles of the infrared pulses relative to the sample surface. By application of this method and using a recently developed theory, it was possible to extract both the out-of-plane and "mainly"-in-plane orientational correlation functions in a model-independent manner. The observed correlation functions were compared with theoretically derived correlation functions based on several dynamical models. The out-of-plane correlation function reveals the highly restricted out-of-plane motions of the head groups and also suggests that the angular distribution of the transition dipole moments is bimodal. The mainly-in-plane correlation function, for the sample studied here with the strongly restricted out-of-plane motions, essentially arises from the purely in-plane dynamics. In contrast to the out-of-plane dynamics, significant in-plane motions occurring over various time scales were observed including an inertial motion, a restricted wobbling motion of ∼3 ps, and complete randomization occurring in ∼25 ps.

    View details for PubMedID 27668512

  • The Influence of Water on the Alkyl Region Structure in Variable Chain Length Imidazolium-Based Ionic Liquid/Water Mixtures JOURNAL OF PHYSICAL CHEMISTRY B Thomaz, J. E., Lawler, C. M., Fayer, M. D. 2016; 120 (39): 10350-10357

    Abstract

    Solutions of room temperature ionic liquids (RTILs) and water were studied by observing the reorientational dynamics of the fluorescent probe perylene. Perylene is solvated in the alkyl regions of the RTILs. Its D2h symmetry made it possible to extract dynamical information on both in-plane and out-of-plane reorientation from time-resolved fluorescence anisotropy measurements. Perylene reorientation reports on its interactions with the alkyl chains. The RTILs were a series of 1-alkyl-3-methylimidazolium tetrafluoroborates (CnmimBF4, where n is the number of carbons in the alkyl chain), and the effects on perylene's dynamics were observed when varying the alkyl chain length of the cation (n = 4, 6, 8, and 10; butyl, hexyl, octyl, decyl) and varying the water content from pure RTIL to roughly three water molecules per RTIL ion pair. Time correlated single photon counting was used to measure the fluorescence anisotropy decays to determine the orientational dynamics. The friction coefficients for both the in-plane and out-of-plane reorientation were determined to eliminate the influence of changes in viscosity caused by both the addition of water and the different alkyl chain lengths. The friction coefficients provided information on the interactions of the perylene with the alkyl environment and how these interactions changed with chain length and water content. As the chain length increased, the addition of water had less of an effect on the local alkyl environment surrounding the perylene. The friction coefficients generally increased with higher water contents; the in-plane orientational motion was hindered significantly more than the out-of-plane motion. The restructuring of the alkyl regions is likely a consequence of a rearrangement of the ionic imidazolium head groups to accommodate partial solvation by water, which results in a change in the arrangement of the alkyl chains. At very high water content, BmimBF4 broke this general trend, with both in-plane and out-of-plane rotational friction decreasing above a water content of one water per ion pair. This decrease indicates a major reorganization of the overall liquid structure in high water content mixtures. In contrast to BmimBF4, the longer chain length RTILs are not infinitely miscible with water, and do not show evidence of a major reorganization before reaching saturation and phase-separating. The results suggest that phase separation in longer chain length BF4 RTILs is a consequence of their inability to undergo the reorganization of the alkyl regions necessary to accommodate high water concentrations.

    View details for DOI 10.1021/acs.jpcb.6b07853

    View details for Web of Science ID 000384959200018

    View details for PubMedID 27643808

  • Ionic Liquid versus Li+ Aqueous Solutions: Water Dynamics near Bistriflimide Anions JOURNAL OF PHYSICAL CHEMISTRY B Giammanco, C. H., Kramer, P. L., Fayer, M. D. 2016; 120 (37): 9997-10009

    Abstract

    The ultrafast dynamics of concentrated aqueous solutions of the salt lithium bistriflimide and ionic liquid (IL) 1-ethyl-3-methylimidazolium bistriflimide was studied using two-dimensional infrared (2D IR) vibrational echo and polarization-selective IR pump-probe techniques to monitor water's hydroxyl stretch. Two distinct populations of hydroxyl groups, with differing vibrational lifetimes, are detected in solution: those engaged in hydrogen bonding with other water molecules and those engaged in hydrogen bonding with the bistriflimide anion. Water molecules with the same hydrogen bond partner exhibit similar vibrational lifetimes in the two solutions. The reorientation dynamics of the anion-associated waters is also similar in form in the two solutions, showing a restricted wobbling-in-a-cone motion followed by a slower diffusive orientational randomization. However, the wobbling motions are much more angularly restricted in the IL solution. Spectral diffusion dynamics, which tracks the structural fluctuations of water's hydrogen bonds, is very different in the two solutions. Water in the IL solution experiences much faster fluctuations overall and shows a greater extent of motional narrowing, resulting in a larger homogeneously broadened component in the spectral line, compared to those in the aqueous lithium salt. Thus, even when the hydroxyls of water associate with the same anion in solution, the cation identity and extent of ionic ordering (i.e., salt solution vs IL) can play an important role in determining the structural fluctuations experienced by a small hydrogen-bonded solute.

    View details for DOI 10.1021/acs.jpcb.6b07145

    View details for Web of Science ID 000384034100017

    View details for PubMedID 27580210

  • Alkyl Chain Length Dependence of the Dynamics and Structure in the Ionic Regions of Room-Temperature Ionic Liquids. journal of physical chemistry. B Tamimi, A., Bailey, H. E., Fayer, M. D. 2016; 120 (30): 7488-7501

    Abstract

    The dynamics of four 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room-temperature ionic liquids (RTILs) with carbon chain lengths of 2, 4, 6, and 10 were studied by measuring the orientational and spectral diffusion dynamics of the vibrational probe SeCN(-). Vibrational absorption spectra, two-dimensional infrared (2D IR), and polarization-selective pump-probe (PSPP) experiments were performed on the CN stretch. In addition, optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments were performed on the bulk liquids. The PSPP experiments yielded triexponential anisotropy decays, which were analyzed with the wobbling-in-a-cone model. The slowest decay, the complete orientational randomization, slows with increasing chain length in a hydrodynamic trend consistent with the increasing viscosity. The shortest time scale wobbling motions are insensitive to chain length, while the intermediate time scale wobbling slows mildly as the chain length increases. The 2D IR spectra measured in parallel (⟨XXXX⟩) and perpendicular (⟨XXYY⟩) polarization configurations gave different decays, showing that reorientation-induced spectral diffusion (RISD) contributes to the dynamics. The spectral diffusion caused by the RTIL structural fluctuations was obtained by removing the RISD contributions. The faster structural fluctuations are relatively insensitive to chain length. The slowest structural fluctuations slow substantially when going from Emim (2 carbon chain) to Bmim (4 carbon chain) and slow further, but more gradually, as the chain length is increased. It was shown previously that K(+) causes local ion clustering in the Emim RTIL. The K(+) effect increases with increasing chain length. The OHD-OKE measured complete structural randomization times slow substantially with increasing chain length and are much slower than the dynamics experienced by the SeCN(-) located in the ionic regions of the RTILs.

    View details for DOI 10.1021/acs.jpcb.6b05397

    View details for PubMedID 27388422

  • Water of Hydration Dynamics in Minerals Gypsum and Bassanite: Ultrafast 2D IR Spectroscopy of Rocks. Journal of the American Chemical Society Yan, C., Nishida, J., Yuan, R., Fayer, M. D. 2016; 138 (30): 9694-9703

    Abstract

    Water of hydration plays an important role in minerals, determining their crystal structures and physical properties. Here ultrafast nonlinear infrared (IR) techniques, two-dimensional infrared (2D IR) and polarization selective pump-probe (PSPP) spectroscopies, were used to measure the dynamics and disorder of water of hydration in two minerals, gypsum (CaSO4·2H2O) and bassanite (CaSO4·0.5H2O). 2D IR spectra revealed that water arrangement in freshly precipitated gypsum contained a small amount of inhomogeneity. Following annealing at 348 K, water molecules became highly ordered; the 2D IR spectrum became homogeneously broadened (motional narrowed). PSPP measurements observed only inertial orientational relaxation. In contrast, water in bassanite's tubular channels is dynamically disordered. 2D IR spectra showed a significant amount of inhomogeneous broadening caused by a range of water configurations. At 298 K, water dynamics cause spectral diffusion that sampled a portion of the inhomogeneous line width on the time scale of ∼30 ps, while the rest of inhomogeneity is static on the time scale of the measurements. At higher temperature, the dynamics become faster. Spectral diffusion accelerates, and a portion of the lower temperature spectral diffusion became motionally narrowed. At sufficiently high temperature, all of the dynamics that produced spectral diffusion at lower temperatures became motionally narrowed, and only homogeneous broadening and static inhomogeneity were observed. Water angular motions in bassanite exhibit temperature-dependent diffusive orientational relaxation in a restricted cone of angles. The experiments were made possible by eliminating the vast amount of scattered light produced by the granulated powder samples using phase cycling methods.

    View details for DOI 10.1021/jacs.6b05589

    View details for PubMedID 27385320

  • Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory. journal of physical chemistry. B Sokolowsky, K. P., Bailey, H. E., Hoffman, D. J., Andersen, H. C., Fayer, M. D. 2016; 120 (28): 7003-7015

    Abstract

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid.

    View details for DOI 10.1021/acs.jpcb.6b04997

    View details for PubMedID 27363680

  • Structural and Rotational Dynamics of Carbon Dioxide in 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids: The Effect of Chain Length JOURNAL OF PHYSICAL CHEMISTRY B Giammanco, C. H., Yamada, S. A., Kramer, P. L., Tamimi, A., Fayer, M. D. 2016; 120 (27): 6698-6711

    Abstract

    Ionic liquids (ILs) have been proposed as possible carbon dioxide (CO2) capture media; thus, it is useful to understand the dynamics of both the dissolved gas and its IL environment as well as how altering an IL affects these dynamics. With increasing alkyl chain length, it is well-established that ILs obtain a mesoscopic structural feature assigned to polar-apolar segregation, and the change in structure with chain length affects the dynamics. Here, the dynamics of CO2 in a series of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ILs, in which the alkyl group is ethyl, butyl, hexyl, or decyl, were investigated using ultrafast infrared spectroscopy by measuring the reorientation and spectral diffusion of carbon dioxide in the ILs. It was found that reorientation of the carbon dioxide occurs on three time scales, which correspond to two different time scales of restricted wobbling-in-a-cone motions and a long-time complete diffusive reorientation. Complete reorientation slows with increasing chain length but less than the increases in viscosity of the bulk liquids. Spectral diffusion, measured with two-dimensional IR spectroscopy, is caused by a combination of the liquids' structural fluctuations and reorientation of the CO2. The data were analyzed using a recent theory that takes into account both contributions to spectral diffusion and extracts the structural spectral diffusion. Different components of the structural fluctuations have distinct dependences on the alkyl chain length. All of the dynamics are fast compared to the complete orientational randomization of the bulk ILs, as measured with optical heterodyne-detected optical Kerr effect measurements. The results indicate a hierarchy of constraint releases in the liquids that give rise to increasingly slower dynamics.

    View details for DOI 10.1021/acs.jpcb.6b03971

    View details for Web of Science ID 000379991000024

    View details for PubMedID 27264965

  • Ionic Liquid Dynamics Measured with 2D IR and IR Pump-Probe Experiments on a Linear Anion and the Influence of Potassium Cations JOURNAL OF PHYSICAL CHEMISTRY B Tamimi, A., Fayer, M. D. 2016; 120 (26): 5842-5854

    Abstract

    The room-temperature ionic liquid EmimNTf2 (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) was studied with two-dimensional infrared (2D IR) spectroscopy and polarization selective pump-probe (PSPP) experiments using low-concentration selenocyanate (SeCN(-)) as the vibrational probe. SeCN(-) was added as EmimSeCN, which keeps the cation the same. KSeCN was also used, so K(+) was added. Two 2D IR polarization configurations were employed: ⟨XXXX⟩ (all pulses have the same polarization) and ⟨XXYY⟩ (the first two pulse polarizations are perpendicular to that of the third pulse and the echo). The spectral diffusion differs for the two configurations, demonstrating that reorientation-induced spectral diffusion, in addition to structural spectral diffusion (SSD), plays a role in the observed dynamics. The SSD was extracted from the 2D IR time-dependent data. The samples with EmimSeCN have dynamics on several fast time scales; however, when KSeCN is used, both the PPSP anisotropy decay and the 2D IR decays have low amplitude offsets (nondecaying values at long times). The size of the offsets increased with increased K(+) concentration. These results are explained in terms of a two-ensemble model. A small fraction of the SeCN(-) is located in the regions modified by the presence of K(+), causing a substantial slowing of the SeCN(-) orientational relaxation and spectral diffusion. Having a small ensemble of SeCN(-) that undergoes very slow dynamics is sufficient to explain the offsets. For the major ensemble, the dynamics with and without K(+) are the same.

    View details for DOI 10.1021/acs.jpcb.6b00409

    View details for Web of Science ID 000379457200008

    View details for PubMedID 26872207

  • Quasi-rotating frame: accurate line shape determination with increased efficiency in noncollinear 2D optical spectroscopy JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Kramer, P. L., Giammanco, C. H., Tamimi, A., Hoffman, D. J., Sokolowsky, K. P., Fayer, M. D. 2016; 33 (6): 1143-1156
  • Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Yan, C., Yuan, R., Pfalzgraff, W. C., Nishida, J., Wang, L., Markland, T. E., Fayer, M. D. 2016; 113 (18): 4929-4934

    Abstract

    Functionalized self-assembled monolayers (SAMs) are the focus of ongoing investigations because they can be chemically tuned to control their structure and dynamics for a wide variety of applications, including electrochemistry, catalysis, and as models of biological interfaces. Here we combine reflection 2D infrared vibrational echo spectroscopy (R-2D IR) and molecular dynamics simulations to determine the relationship between the structures of functionalized alkanethiol SAMs on gold surfaces and their underlying molecular motions on timescales of tens to hundreds of picoseconds. We find that at higher head group density, the monolayers have more disorder in the alkyl chain packing and faster dynamics. The dynamics of alkanethiol SAMs on gold are much slower than the dynamics of alkylsiloxane SAMs on silica. Using the simulations, we assess how the different molecular motions of the alkyl chain monolayers give rise to the dynamics observed in the experiments.

    View details for DOI 10.1073/pnas.1603080113

    View details for Web of Science ID 000375395700026

    View details for PubMedID 27044113

    View details for PubMedCentralID PMC4983838

  • Carbon dioxide in an ionic liquid: Structural and rotational dynamics JOURNAL OF CHEMICAL PHYSICS Giammanco, C. H., Kramer, P. L., Yamada, S. A., Nishida, J., Tamimi, A., Fayer, M. D. 2016; 144 (10)

    Abstract

    Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. To inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO2), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral diffusion contribution, the previously developed first order Stark effect RISD model is reformulated to describe the second order (quadratic) Stark effect-the first order Stark effect vanishes because CO2 does not have a permanent dipole moment. Through this analysis, we characterize the structural fluctuations of CO2 in the ionic liquid solvation environment, which separate into magnitude-only and combined magnitude and directional correlations of the liquid's time dependent electric field. This new methodology will enable highly incisive comparisons between CO2 dynamics in a variety of ionic liquid systems.

    View details for DOI 10.1063/1.4943390

    View details for Web of Science ID 000372974600024

  • Coupling of Carbon Dioxide Stretch and Bend Vibrations Reveals Thermal Population Dynamics in an Ionic Liquid. journal of physical chemistry. B Giammanco, C. H., Kramer, P. L., Yamada, S. A., Nishida, J., Tamimi, A., Fayer, M. D. 2016; 120 (3): 549-556

    Abstract

    The population relaxation of carbon dioxide dissolved in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) was investigated using polarization-selective ultrafast infrared pump-probe spectroscopy and two-dimensional infrared (2D IR) spectroscopy. Due to the coupling of the bend with the asymmetric stretch, excitation of the asymmetric stretch of a molecule with a thermally populated bend leads to an additional peak, a hot band, which is red-shifted from the main asymmetric absorption band by the combination band shift. This hot band peak exchanges population with the main peak through the gain and loss of bend excitation quanta. The isotropic pump-probe signal originating from the unexcited bend state displays a fast, relatively small amplitude, initial growth followed by a longer time scale exponential decay. The signal is analyzed over its full time range using a kinetic model to determine both the vibrational lifetime (the final decay) and rate constant for the loss of the bend energy. This bend relaxation manifests as the fast initial growth of the stretch/no bend signal because the hot band (stretch with bend) is "over pumped" relative to the ground state equilibrium. The nonequilibrium pumping occurs because the hot band has a larger transition dipole moment than the stretch/no bend peak. The system is then prepared, utilizing an acousto-optic mid-infrared pulse shaper to cut a hole in the excitation pulse spectrum, such that the hot band is not pumped. The isotropic pump-probe signal from the stretch/no bend state is altered because the initial excited state population ratio has changed. Instead of a growth due to relaxation of bend quanta, a fast initial decay is observed because of thermal excitation of the bend. Fitting this curve gives the rate constant for thermal excitation of the bend and the lifetime, which agree with those determined in the pump-probe experiments without frequency-selective pumping.

    View details for DOI 10.1021/acs.jpcb.5b11454

    View details for PubMedID 26731088

  • Molecular Anion Hydrogen Bonding Dynamics in Aqueous Solution. journal of physical chemistry. B Yuan, R., Yan, C., Tamimi, A., Fayer, M. D. 2015; 119 (42): 13407-13415

    View details for DOI 10.1021/acs.jpcb.5b08168

    View details for PubMedID 26434772

  • Separation of experimental 2D IR frequency-frequency correlation functions into structural and reorientation-induced contributions. journal of chemical physics Kramer, P. L., Nishida, J., Fayer, M. D. 2015; 143 (12): 124505-?

    Abstract

    A vibrational transition frequency can couple to its environment through a directional vector interaction. In such cases, reorientation of the vibrational transition dipole (molecular orientational relaxation) and its frequency fluctuations can be strongly coupled. It was recently shown [Kramer et al., J. Chem. Phys. 142, 184505 (2015)] that differing frequency-frequency correlation function (FFCF) decays, due to reorientation-induced spectral diffusion (RISD), are observed with different two-dimensional infrared polarization configurations when such strong coupling is present. The FFC functional forms were derived for the situation in which all spectral diffusion is due to reorientational motion. We extend the previous theory to include vibrational frequency evolution (spectral diffusion) caused by structural fluctuations of the medium. Model systems with diffusive reorientation and several regimes of structural spectral diffusion rates are analyzed for first order Stark effect interactions. Additionally, the transition dipole reorientational motion in complex environments is frequently not completely diffusive. Several periods of restricted angular motion (wobbling-in-a-cone) may precede the final diffusive orientational randomization. The polarization-weighted FFCF decays are presented in this case of restricted transition dipole wobbling. With these extensions to the polarization-dependent FFCF expressions, the structural spectral diffusion dynamics of methanol in the room temperature ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate can be separated quantitatively from RISD using the experimental center line slope data. In addition, prior results on the spectral diffusion of water, methanol, and ethanol in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are re-examined to elucidate the influence of reorientation on the data, which were interpreted in terms of structural fluctuations.

    View details for DOI 10.1063/1.4931402

    View details for PubMedID 26429022

  • Separation of experimental 2D IR frequency-frequency correlation functions into structural and reorientation-induced contributions. journal of chemical physics Kramer, P. L., Nishida, J., Fayer, M. D. 2015; 143 (12): 124505-?

    Abstract

    A vibrational transition frequency can couple to its environment through a directional vector interaction. In such cases, reorientation of the vibrational transition dipole (molecular orientational relaxation) and its frequency fluctuations can be strongly coupled. It was recently shown [Kramer et al., J. Chem. Phys. 142, 184505 (2015)] that differing frequency-frequency correlation function (FFCF) decays, due to reorientation-induced spectral diffusion (RISD), are observed with different two-dimensional infrared polarization configurations when such strong coupling is present. The FFC functional forms were derived for the situation in which all spectral diffusion is due to reorientational motion. We extend the previous theory to include vibrational frequency evolution (spectral diffusion) caused by structural fluctuations of the medium. Model systems with diffusive reorientation and several regimes of structural spectral diffusion rates are analyzed for first order Stark effect interactions. Additionally, the transition dipole reorientational motion in complex environments is frequently not completely diffusive. Several periods of restricted angular motion (wobbling-in-a-cone) may precede the final diffusive orientational randomization. The polarization-weighted FFCF decays are presented in this case of restricted transition dipole wobbling. With these extensions to the polarization-dependent FFCF expressions, the structural spectral diffusion dynamics of methanol in the room temperature ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate can be separated quantitatively from RISD using the experimental center line slope data. In addition, prior results on the spectral diffusion of water, methanol, and ethanol in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are re-examined to elucidate the influence of reorientation on the data, which were interpreted in terms of structural fluctuations.

    View details for DOI 10.1063/1.4931402

    View details for PubMedID 26429022

  • Dynamics of water, methanol, and ethanol in a room temperature ionic liquid JOURNAL OF CHEMICAL PHYSICS Kramer, P. L., Giammanco, C. H., Fayer, M. D. 2015; 142 (21)

    Abstract

    The dynamics of a series of small molecule probes with increasing alkyl chain length: water, methanol, and ethanol, diluted to low concentration in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was investigated with 2D infrared vibrational echo (2D IR) spectroscopy and polarization resolved pump-probe (PP) experiments on the deuterated hydroxyl (O-D) stretching mode of each of the solutes. The long timescale spectral diffusion observed by 2D IR, capturing complete loss of vibrational frequency correlation through structural fluctuation of the medium, shows a clear but not dramatic slowing as the probe alkyl chain length is increased: 23 ps for water, 28 ps for methanol, and 34 ps for ethanol. Although in each case, only a single population of hydroxyl oscillators contributes to the infrared line shapes, the isotropic pump-probe decays (normally caused by population relaxation) are markedly nonexponential at short times. The early time features correspond to the timescales of the fast spectral diffusion measured with 2D IR. These fast isotropic pump-probe decays are produced by unequal pumping of the OD absorption band to a nonequilibrium frequency dependent population distribution caused by significant non-Condon effects. Orientational correlation functions for these three systems, obtained from pump-probe anisotropy decays, display several periods of restricted angular motion (wobbling-in-a-cone) followed by complete orientational randomization. The cone half-angles, which characterize the angular potential, become larger as the experimental frequency moves to the blue. These results indicate weakening of the angular potential with decreasing hydrogen bond strength. The slowest components of the orientational anisotropy decays are frequency-independent and correspond to the complete orientational randomization of the solute molecule. These components slow appreciably with increasing chain length: 25 ps for water, 42 ps for methanol, and 88 ps for ethanol. The shape and volume of the probe, therefore, impact reorientation far more severely than they do spectral diffusion at long times, though these two processes occur on similar timescales at earlier times.

    View details for DOI 10.1063/1.4914156

    View details for Web of Science ID 000355931800012

    View details for PubMedID 26049428

  • Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy. journal of chemical physics Kramer, P. L., Nishida, J., Giammanco, C. H., Tamimi, A., Fayer, M. D. 2015; 142 (18): 184505-?

    Abstract

    In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.

    View details for DOI 10.1063/1.4920949

    View details for PubMedID 25978898

  • Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy JOURNAL OF CHEMICAL PHYSICS Kramer, P. L., Nishida, J., Giammanco, C. H., Tamimi, A., Fayer, M. D. 2015; 142 (18)

    Abstract

    In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.

    View details for DOI 10.1063/1.4920949

    View details for Web of Science ID 000354775800023

    View details for PubMedID 25978898

  • Dynamics of dihydrogen bonding in aqueous solutions of sodium borohydride. journal of physical chemistry. B Giammanco, C. H., Kramer, P. L., Fayer, M. D. 2015; 119 (8): 3546-3559

    View details for DOI 10.1021/jp512426y

    View details for PubMedID 25635342

  • Dynamics of dihydrogen bonding in aqueous solutions of sodium borohydride. journal of physical chemistry. B Giammanco, C. H., Kramer, P. L., Fayer, M. D. 2015; 119 (8): 3546-3559

    View details for DOI 10.1021/jp512426y

    View details for PubMedID 25635342

  • Dynamics and structure of room temperature ionic liquids CHEMICAL PHYSICS LETTERS Fayer, M. D. 2014; 616: 259-274
  • Length Scales and Structural Dynamics in Nematogen Pseudonematic Domains Measured with 2D IR Vibrational Echoes and Optical Kerr Effect Experiments. journal of physical chemistry. B Sokolowsky, K. P., Bailey, H. E., Fayer, M. D. 2014; 118 (28): 7856-7868

    Abstract

    Nematogen liquids in the isotropic phase are macroscopically homogeneous but on multinanometer length scales have pseudonematic domains with correlation lengths that grow as the isotropic to nematic phase transition temperature (TNI) is approached from above. Orientational relaxation of nematogens in the isotropic phase manifests as two fast power laws and a slow exponential decay when measured by optical heterodyne detected optical Kerr effect (OHD-OKE) experiments. The long time exponential relaxation is associated with complete randomization of pseudonematic domains. We examine the effect of local orientational correlation on spectral diffusion (structural evolution) experienced by a vibrational probe molecule within the pseudonematic domains of 4-cyano-4'-pentylbiphenyl (5CB) using two-dimensional infrared (2D IR) vibrational echo spectroscopy. The addition of low concentration 4-pentyl-4'-thiocyanobiphenyl (5SCB) as a long-lived vibrational probe to 5CB is shown to lower TNI of the sample slightly, but the fast power law dynamics and exponential decays observed by OHD-OKE spectroscopy are unchanged. We compare the complete orientational relaxation and spectral diffusion for samples of 5SCB in 5CB to 5SCB in 4-pentylbiphenyl (5B) at four temperatures above TNI. 5B has a molecular structure similar to 5CB but is not a nematogen. At all but the lowest temperature, the spectral diffusion in 5CB and 5B is described well as a triexponential decay with very similar time constants. The results demonstrate that the presence of local orientational order at temperatures well above TNI does not affect the spectral diffusion (structural evolution) within pseudonematic domains when the correlation lengths are short. However, when the temperature of the sample is held very close to TNI, the spectral diffusion in 5CB slows dramatically while that in 5B does not. It is only as the correlation length becomes very long that its presence impacts the spectral diffusion (structural fluctuations) sensed by the vibrational probes located in pseudonematic domains. The orientational relaxation is modeled with schematic mode coupling theory (MCT). Fitting with MCT provides density and orientational correlation functions. The density correlation decays are similar for 5B and 5CB, but the orientational correlation decays are much slower for 5CB. Additionally, the time dependence of the spectral diffusion in 5CB is strikingly similar to that of the density correlation function decay, while the orientational correlation function decay is far too slow to contribute to the spectral diffusion. Therefore, density fluctuations are likely the source of spectral diffusion at temperatures at least 5 K above TNI.

    View details for DOI 10.1021/jp500144p

    View details for PubMedID 24521155

  • Theory of third-order spectroscopic methods to extract detailed molecular orientational dynamics for planar surfaces and other uniaxial systems. journal of chemical physics Nishida, J., Fayer, M. D. 2014; 140 (14): 144702-?

    Abstract

    Functionalized organic monolayers deposited on planar two-dimensional surfaces are important systems for studying ultrafast orientational motions and structures of interfacial molecules. Several studies have successfully observed the orientational relaxation of functionalized monolayers by fluorescence depolarization experiments and recently by polarization-resolved heterodyne detected vibrational transient grating (HDTG) experiments. In this article we provide a model-independent theory to extract orientational correlation functions unique to interfacial molecules and other uniaxial systems based on polarization-resolved resonant third-order spectroscopies, such as pump-probe spectroscopy, HDTG spectroscopy, and fluorescence depolarization experiment. It will be shown (in the small beam-crossing angle limit) that five measurements are necessary to completely characterize the monolayer's motions: I(∥)(t) and I(⊥)(t) with the incident beams normal to the surface, I(∥)(t) and I(⊥)(t) with a non-zero incident angle, and a time averaged linear dichroism measurement. Once these measurements are performed, two orientational correlation functions corresponding to in-plane and out-of-plane motions are obtained. The procedure is applicable not only for monolayers on flat surfaces, but any samples with uniaxial symmetry such as uniaxial liquid crystals and aligned planar bilayers. The theory is valid regardless of the nature of the actual molecular motions on interface. We then apply the general results to wobbling-in-a-cone model, in which molecular motions are restricted to a limited range of angles. Within the context of the model, the cone angle, the tilt of the cone relative to the surface normal, and the orientational diffusion constant can be determined. The results are extended to describe analysis of experiments where the beams are not crossing in the small angle limit.

    View details for DOI 10.1063/1.4870436

    View details for PubMedID 24735308

  • Theory of third-order spectroscopic methods to extract detailed molecular orientational dynamics for planar surfaces and other uniaxial systems JOURNAL OF CHEMICAL PHYSICS Nishida, J., Fayer, M. D. 2014; 140 (14)

    View details for DOI 10.1063/1.4870436

    View details for Web of Science ID 000334836600028

    View details for PubMedID 24735308

  • Size-dependent ultrafast structural dynamics inside phospholipid vesicle bilayers measured with 2D IR vibrational echoes PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kel, O., Tamimi, A., Fayer, M. D. 2014; 111 (3): 918-923

    Abstract

    The ultrafast structural dynamics inside the bilayers of dilauroylphosphatidylcholine (DLPC) and dipalmitoylphosphatidylcholine vesicles with 70, 90, and 125 nm diameters were directly measured with 2D IR vibrational echo spectroscopy. The antisymmetric CO stretch of tungsten hexacarbonyl was used as a vibrational probe and provided information on spectral diffusion (structural dynamics) in the alkyl region of the bilayers. Although the CO stretch absorption spectra remain the same, the interior structural dynamics become faster as the size of the vesicles decrease, with the size dependence greater for dipalmitoylphosphatidylcholine than for DLPC. As DLPC vesicles become larger, the interior dynamics approach those of the planar bilayer.

    View details for DOI 10.1073/pnas.1323110111

    View details for Web of Science ID 000329928400026

    View details for PubMedID 24395796

    View details for PubMedCentralID PMC3903213

  • Dynamics of Molecular Monolayers with Different Chain Lengths in Air and Solvents Probed by Ultrafast 2D IR Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY C Nishida, J., Yan, C., Fayer, M. D. 2014; 118 (1): 523-532

    View details for DOI 10.1021/jp410683h

    View details for Web of Science ID 000329678200056

  • The Influence of Cholesterol on Fast Dynamics Inside of Vesicle and Planar Phospholipid Bilayers Measured with 2D IR Spectroscopy J. Phys. Chem B. Kel, O., Tamimi, A., Michael, F. D. 2014
  • Dynamics in the isotropic phase of nematogens using 2D IR vibrational echo measurements on natural-abundance 13CN and extended lifetime probes. journal of physical chemistry. B Sokolowsky, K. P., Fayer, M. D. 2013; 117 (48): 15060-15071

    Abstract

    The long time scale orientational relaxation of nematogens in the isotropic phase is associated with the randomization of pseudonematic domains, which have a correlation length that grows as the isotropic-to-nematic phase transition temperature is approached from above. Here we begin to address the fast dynamics of the nematogen molecules within the domains using two-dimensional infrared (2D IR) vibrational echo experiments. The problems of performing ultrafast IR experiments in pure liquids are discussed, and solutions are presented. In addition, the issue of short vibrational lifetimes, which limit the ability of 2D IR experiments to examine dynamics over a wide range of times, is addressed. The experiments were performed on the nematogen 4-cyano-4'-pentylbiphenyl (5CB), with the CN stretch initially used as the vibrational probe. Although the CN stretch has a small transition dipole, because the sample is a pure liquid it is necessary to use an exceedingly thin sample to perform the experiments. The small sample volume leads to massive heating effects that distort the results. In addition, the high concentration in the pure liquid can result in vibrational excitation transfer that interferes with the measurements of structural dynamics, and the CN vibrational lifetime is very short (3.6 ps). These problems were overcome by performing the experiments on the natural-abundance (13)CN stretch (5(13)CB), which greatly reduced the absorbance, eliminating the heating problems; also, this stretch has a longer lifetime (7.9 ps). Experiments were also performed on benzonitrile, which showed that the heating problems associated with pure liquids are not unique to 5CB. Again, the problems were eliminated by conducting measurements on the (13)CN stretch, which has an even longer lifetime (20.2 ps) compared with the (12)CN stretch (5.6 ps). Finally, to extend the range of the dynamical measurements, 4-pentyl-4'-thiocyanobiphenyl (5SCB) was synthesized and studied as a dilute solute in 5CB. The CN stretch of 5SCB has a vibrational lifetime of 103 ps, which permits dynamical measurements to 200 ps, revealing the full range of fast structural dynamics in the isotropic phase of 5CB. It is shown that the 5SCB probe reports essentially the same dynamics as 5(13)CB on the short time scale that is observable with the 5(13)CB vibrational probe.

    View details for DOI 10.1021/jp4071955

    View details for PubMedID 24156524

  • Orientational dynamics in a lyotropic room temperature ionic liquid. journal of physical chemistry. B Sturlaugson, A. L., Arima, A. Y., Bailey, H. E., Fayer, M. D. 2013; 117 (47): 14775-14784

    Abstract

    In a previous study of room temperature ionic liquid/water mixtures, the first clearly observed biexponential decays in optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments on a liquid were reported, (Sturlaugson, A. L.; Fruchey, K. S.; Fayer, M. D. J. Phys. Chem. B 2012, 116, 1777), and it was suggested that the biexponential behavior is indicative of the approach to gelation. Here, new OHD-OKE experiments on mixtures of the room temperature ionic liquid 1-methyl-3-octylimidazolium chloride (OmimCl) with water are presented. The OmimCl/water system is shown to gel over the water mole fraction range of 0.69-0.81. In the OHD-OKE decays, the biexponential behavior becomes more distinct as the gelling concentration range is approached from either high or low water concentrations. The biexponential decays are analyzed in terms of the wobbling-in-a-cone model, and the resulting diffusion constants and "relative" order parameters and cone angles are reported. Comparison of the OmimCl/water data with the previously reported room temperature ionic liquid/water OHD-OKE decays supports the previous hypothesis that the biexponential dynamics are due to the approach to the liquid-gel transition and suggests that the order of the concentration-dependent phase transition can be tuned by the choice of anion.

    View details for DOI 10.1021/jp407325b

    View details for PubMedID 24171452

  • Theoretical examination of picosecond phenol migration dynamics in phenylacetylene solution CHEMICAL PHYSICS Kocia, L., Young, S. M., Kholod, Y. A., Fayer, M. D., Gordon, M. S., Rappe, A. M. 2013; 422: 175-183
  • The influence of lithium cations on dynamics and structure of room temperature ionic liquids. journal of physical chemistry. B Lawler, C., Fayer, M. D. 2013; 117 (33): 9768-9774

    Abstract

    The orientational relaxation dynamics of perylene in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide were studied as a function of lithium ion concentration. Perylene is nonpolar and locates in the alkyl regions of the RTIL. The lithium cation was added as lithium bis(trifluoromethyl)sulfonyl imide, so the addition of Li(+) did not change the anion. The Li(+) concentration ranged from 0 to 0.4 mol fraction. The dynamics were measured by observing the fluorescence anisotropy decay using time correlated single photon counting. The anisotropy experiments and viscosity measurements were performed as a function of temperature for each Li(+) concentration sample. Because perylene has high symmetry, it was possible to independently determine the in-plane and out-of-plane diffusion constants and friction coefficients. With increasing concentration of lithium salt the viscosity increases and both the in-plane and out-of-plane orientational relaxations of perylene become slower. However, the corresponding molecular friction coefficients decreased, with the in-plane coefficient decreasing to a greater extent than the out-of-plane coefficient. The decrease in the friction coefficients demonstrates that lithium ions, which are located in the ionic regions of the RTILs, change the structure of the alkyl regions of the RTIL.

    View details for DOI 10.1021/jp405752q

    View details for PubMedID 23879633

  • The Influence of Lithium Cations on Dynamics and Structure of Room Temperature Ionic Liquids JOURNAL OF PHYSICAL CHEMISTRY B Lawler, C., Fayer, M. D. 2013; 117 (33): 9768-9774

    View details for DOI 10.1021/jp405752q

    View details for Web of Science ID 000323593500020

    View details for PubMedID 23879633

  • Ultrafast Structural Dynamics Inside Planar Phospholipid Multibilayer Model Cell Membranes Measured with 2D IR Spectroscopy. Journal of the American Chemical Society Kel, O., Tamimi, A., Thielges, M. C., Fayer, M. D. 2013; 135 (30): 11063-11074

    Abstract

    The ultrafast dynamics in the interior of planar aligned multibilayers of 1,2-dilauroyl-sn-glycero-3-phosphocholine (dilauroylphosphatidylcholine, DLPC) are investigated using 2D IR vibrational echo spectroscopy. The nonpolar and water insoluble vibrational dynamics probe, tungsten hexacarbonyl (W(CO)6), is located in the alkane interior of the membranes. The 2D IR experiments conducted on the antisymmetric CO stretching mode measure spectral diffusion caused by the structural dynamics of the membrane from ∼200 fs to ∼200 ps as a function of the number of water molecules hydrating the head groups and as a function of cholesterol content for a fixed hydration level. FT-IR studies of the lipid bilayers and the model liquids, hexadecane and bis(2-ethylhexyl) succinate, indicate that as the number of hydrating water molecules increases from 2 to 16, there are structural changes in the membrane that partition some of the W(CO)6 into the ester region of DLPC. However, the 2D IR measurements, which are made solely on the W(CO)6 in the alkane regions, show that the level of hydration has no observable impact on the interior membrane dynamics. FT-IR spectra and 2D IR experiments on samples with cholesterol concentrations from 0 to 60% demonstrate that there is a change in the membrane structure and an abrupt change in dynamics at 35% cholesterol. The dynamics are independent of cholesterol content from 10 to 35%. At 35%, the dynamics become slower and remain unchanged from 35 to 60% cholesterol.

    View details for DOI 10.1021/ja403675x

    View details for PubMedID 23837718

  • Dynamics in the interior of AOT lamellae investigated with two-dimensional infrared spectroscopy. Journal of the American Chemical Society Kumar, S. K., Tamimi, A., Fayer, M. D. 2013; 135 (13): 5118-5126

    Abstract

    The dynamics inside the organic regions of aerosol-OT (AOT)/water mixtures in the lamellar mesophase, bicontinuous cubic (BC) phase, and in an analogous molecule without the charged sulfonate headgroup are investigated by observing spectral diffusion, orientational relaxation and population relaxation using ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy and IR pump-probe experiments on the asymmetric CO stretch of a vibrational probe, tungsten hexacarbonyl (W(CO)6). The water layer thickness between the bilayer planes in the lamellar phase was varied. For comparison, the dynamics of W(CO)6 in the normal liquid bis(2-ethylhexyl) succinate (EHS), which is analogous to AOT but has no charged sulfonate headgroup, were also studied. The 2D IR experiments measure spectral diffusion, which results from the structural evolution of the system. Spectral diffusion is quantified by the frequency-frequency correlation function (FFCF). In addition to a homogeneous component, the FFCFs are biexponential decays with fast and slow time components of ∼12.5 and ∼150 ps in the lamellar phase. Both components of the FFCF are independent of the number of water molecules per headgroup for the lamellae, but they slow somewhat in the BC phase. The dynamics in the ordered phases are in sharp contrast to the dynamics in EHS, which displays fast and slow components of the FFCF of 5 and 80 ps, respectively. As the hydration level of AOT increases, vibrational lifetime decreases, suggesting some change in the local environment of W(CO)6 with water content.

    View details for DOI 10.1021/ja312676e

    View details for PubMedID 23465101

  • Dynamics in the Interior of AOT Lamellae Investigated with Two-Dimensional Infrared Spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kumar, S. K., Tamimi, A., Fayer, M. D. 2013; 135 (13): 5118-5126

    Abstract

    The dynamics inside the organic regions of aerosol-OT (AOT)/water mixtures in the lamellar mesophase, bicontinuous cubic (BC) phase, and in an analogous molecule without the charged sulfonate headgroup are investigated by observing spectral diffusion, orientational relaxation and population relaxation using ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy and IR pump-probe experiments on the asymmetric CO stretch of a vibrational probe, tungsten hexacarbonyl (W(CO)6). The water layer thickness between the bilayer planes in the lamellar phase was varied. For comparison, the dynamics of W(CO)6 in the normal liquid bis(2-ethylhexyl) succinate (EHS), which is analogous to AOT but has no charged sulfonate headgroup, were also studied. The 2D IR experiments measure spectral diffusion, which results from the structural evolution of the system. Spectral diffusion is quantified by the frequency-frequency correlation function (FFCF). In addition to a homogeneous component, the FFCFs are biexponential decays with fast and slow time components of ∼12.5 and ∼150 ps in the lamellar phase. Both components of the FFCF are independent of the number of water molecules per headgroup for the lamellae, but they slow somewhat in the BC phase. The dynamics in the ordered phases are in sharp contrast to the dynamics in EHS, which displays fast and slow components of the FFCF of 5 and 80 ps, respectively. As the hydration level of AOT increases, vibrational lifetime decreases, suggesting some change in the local environment of W(CO)6 with water content.

    View details for DOI 10.1021/ja312676e

    View details for Web of Science ID 000317259300042

  • Structural Dynamics at Monolayer-Liquid Interfaces Probed by 2D IR Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY C Rosenfeld, D. E., Nishida, J., Yan, C., Kumar, S. K., Tamimi, A., Fayer, M. D. 2013; 117 (3): 1409-1420

    View details for DOI 10.1021/jp311144b

    View details for Web of Science ID 000314205100023

  • Dynamics of Isolated Water Molecules in a Sea of Ions in a Room Temperature Ionic Liquid JOURNAL OF PHYSICAL CHEMISTRY B Wong, D. B., Giammanco, C. H., Fenn, E. E., Fayer, M. D. 2013; 117 (2): 623-635

    View details for DOI 10.1021/jp310086s

    View details for Web of Science ID 000313920300016

    View details for PubMedID 23276306

  • Ultrafast Infrared Vibrational Spectroscopy edited by Fayer, M. D. Francis & Taylor Group, LLC. 2013
  • Water Dynamics in Divalent and Monovalent Concentrated Salt Solutions JOURNAL OF PHYSICAL CHEMISTRY B Giammanco, C. H., Wong, D. B., Fayer, M. D. 2012; 116 (46): 13781-13792

    Abstract

    Water hydrogen bond dynamics in concentrated salt solutions are studied using polarization-selective IR pump-probe spectroscopy and 2D IR vibrational echo spectroscopy performed on the OD hydroxyl stretching mode of dilute HOD in H(2)O/salt solutions. The OD stretch is studied to eliminate vibrational excitation transfer, which interferes with the dynamical measurements. Though previous research suggested that only the anion affected dynamics in solution, here it is shown that the cation plays a role as well. From FT-IR spectra of the OD stretch, it is seen that replacing either ion of the salt pair causes a shift in absorption frequency relative to that of the OD stretch absorption in bulk pure water. This shift becomes pronounced with larger, more polarizable anions or smaller, high charge-density cations. The vibrational lifetime of the OD hydroxyl stretch in these solutions is a local property and is primarily dependent on the nature of the anion and whether the OD is hydrogen bonded to the anion or to the oxygen of another water molecule. However, the cation still has a small effect. Time dependent anisotropy measurements show that reorientation dynamics in these concentrated solutions is a highly concerted process. While the lifetime, a local probe, displays an ion-associated and a bulk-like component in concentrated solutions, the orientational relaxation does not have two subensemble dynamics, as demonstrated by the lack of a wavelength dependence. The orientational relaxation of the single ensemble is dependent on the identity of both the cation and anion. The 2D IR vibrational echo experiments measure spectral diffusion that is caused by structural evolution of the system. The vibrational echo measurements yield the frequency-frequency correlation function (FFCF). The results also show that the structural dynamics are dependent on the cation as well as the anion.

    View details for DOI 10.1021/jp3095402

    View details for Web of Science ID 000311461000023

    View details for PubMedID 23113682

  • Comparisons of 2D IR measured spectral diffusion in rotating frames using pulse shaping and in the stationary frame using the standard method JOURNAL OF CHEMICAL PHYSICS Kumar, S. K., Tamimi, A., Fayer, M. D. 2012; 137 (18)

    Abstract

    Multidimensional visible spectroscopy using pulse shaping to produce pulses with stable controllable phases and delays has emerged as an elegant tool to acquire electronic spectra faster and with greatly reduced instrumental and data processing errors. Recent migration of this approach using acousto-optic modulator (AOM) pulse shaping to the mid-infrared region has proved useful for acquiring two dimensional infrared (2D IR) vibrational echo spectra. The measurement of spectral diffusion in 2D IR experiments hinges on obtaining accurate 2D line shapes. To date, pulse shaping 2D IR has not been used to study the time-dependent spectral diffusion of a vibrational chromophore. Here we compare the spectral diffusion data obtained from a standard non-collinear 2D IR spectrometer using delay lines to the data obtained from an AOM pulse shaper based 2D IR spectrometer. The pulse shaping experiments are performed in stationary, partially rotating, and fully rotating reference frames and are the first in the infrared to produce 2D spectra collected in a fully rotating frame using a phase controlled pulse sequence. Rotating frame experiments provide a dramatic reduction in the number of time points that must be measured to obtain a 2D IR spectrum, with the fully rotating frame giving the greatest reduction. Experiments were conducted on the transition metal carbonyl complex tricarbonylchloro(1,10-phenanthroline)rhenium(I) in chloroform. The time dependent data obtained from the different techniques and with different reference frames are shown to be in agreement.

    View details for DOI 10.1063/1.4764470

    View details for Web of Science ID 000311317800007

  • Comparisons of 2D IR measured spectral diffusion in rotating frames using pulse shaping and in the stationary frame using the standard method. journal of chemical physics Karthick Kumar, S. K., Tamimi, A., Fayer, M. D. 2012; 137 (18): 184201-?

    Abstract

    Multidimensional visible spectroscopy using pulse shaping to produce pulses with stable controllable phases and delays has emerged as an elegant tool to acquire electronic spectra faster and with greatly reduced instrumental and data processing errors. Recent migration of this approach using acousto-optic modulator (AOM) pulse shaping to the mid-infrared region has proved useful for acquiring two dimensional infrared (2D IR) vibrational echo spectra. The measurement of spectral diffusion in 2D IR experiments hinges on obtaining accurate 2D line shapes. To date, pulse shaping 2D IR has not been used to study the time-dependent spectral diffusion of a vibrational chromophore. Here we compare the spectral diffusion data obtained from a standard non-collinear 2D IR spectrometer using delay lines to the data obtained from an AOM pulse shaper based 2D IR spectrometer. The pulse shaping experiments are performed in stationary, partially rotating, and fully rotating reference frames and are the first in the infrared to produce 2D spectra collected in a fully rotating frame using a phase controlled pulse sequence. Rotating frame experiments provide a dramatic reduction in the number of time points that must be measured to obtain a 2D IR spectrum, with the fully rotating frame giving the greatest reduction. Experiments were conducted on the transition metal carbonyl complex tricarbonylchloro(1,10-phenanthroline)rhenium(I) in chloroform. The time dependent data obtained from the different techniques and with different reference frames are shown to be in agreement.

    View details for DOI 10.1063/1.4764470

    View details for PubMedID 23163363

  • Dynamics of Functionalized Surface Molecular Monolayers Studied with Ultrafast Infrared Vibrational Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY C Rosenfeld, D. E., Nishida, J., Yan, C., Gengeliczki, Z., Smith, B. J., Fayer, M. D. 2012; 116 (44): 23428-23440

    Abstract

    The structural dynamics of thin films consisting of tricarbonyl (1,10-phenanthroline)rhenium chloride (RePhen(CO)(3)Cl) linked to an alkyl silane monolayer through a triazole linker synthesized on silica-on-calcium-fluoride substrates are investigated using ultrafast infrared (IR) techniques. Ultrafast 2D IR vibrational echo experiments and polarization selective heterodyne detected transient grating (HDTG) measurements, as well as polarization dependent FT-IR and AFM experiments are employed to study the samples. The vibrational echo experiments measure spectral diffusion, while the HDTG experiments measure the vibrational excited state population relaxation and investigate the vibrational transition dipole orientational anisotropy decay. To investigate the anticipated impact of vibrational excitation transfer, which can be caused by the high concentration of RePhen(CO)(3)Cl in the monolayer, a concentration dependence of the spectral diffusion is measured. To generate a range of concentrations, mixed monolayers consisting of both hydrogen terminated and triazole/RePhen(CO)(3)Cl terminated alkyl silanes are synthesized. It is found that the measured rate of spectral diffusion is independent of concentration, with all samples showing spectral diffusion of 37 ± 6 ps. To definitively test for vibrational excitation transfer, polarization selective HDTG experiments are conducted. Excitation transfer will cause anisotropy decay. Polarization resolved heterodyne detected transient grating spectroscopy is sensitive to anisotropy decay (depolarization) caused by excitation transfer and molecular reorientation. The HDTG experiments show no evidence of anisotropy decay on the appropriate time scale, demonstrating the absence of excitation transfer the RePhen(CO)(3)Cl. Therefore the influence of excitation transfer on spectral diffusion is inconsequential in these samples, and the vibrational echo measurements of spectral diffusion report solely on structural dynamics. A small amount of very fast (~2 ps time scale) anisotropy decay is observed. The decay is concentration independent, and is assigned to wobbling-in-a-cone orientational motions of the RePhen(CO)(3)Cl. Theoretical calculations reported previously for experiments on a single concentration of the same type of sample suggested the presence of some vibrational excitation transfer and excitation transfer induced spectral diffusion. Possible reasons for the experimentally observed lack of excitation transfer in these high concentration samples are discussed.

    View details for DOI 10.1021/jp307677b

    View details for Web of Science ID 000310769300031

    View details for PubMedCentralID PMC3523711

  • Fast Dynamics of HP35 for Folded and Urea-Unfolded Conditions JOURNAL OF PHYSICAL CHEMISTRY B Chung, J. K., Thielges, M. C., Lynch, S. R., Fayer, M. D. 2012; 116 (36): 11024-11031

    Abstract

    The changes in fast dynamics of HP35 with a double CN vibrational dynamics label (HP35-P(2)) as a function of the extent of denaturation by urea were investigated with two-dimensional infrared (2D IR) vibrational echo spectroscopy. Cyanophenylalanine (PheCN) replaces the native phenylalanine at two residues in the hydrophobic core of HP35, providing vibrational probes. NMR data show that HP35-P(2) maintains the native folded structure similar to wild type and that both PheCN residues share essentially the same environment within the peptide. A series of time-dependent 2D IR vibrational echo spectra were obtained for the folded peptide and the increasingly unfolded peptide. Analysis of the time dependence of the 2D spectra yields the system's spectral diffusion, which is caused by the sampling of accessible structures of the peptide under thermal equilibrium conditions. The structural dynamics become faster as the degree of unfolding is increased.

    View details for DOI 10.1021/jp304058x

    View details for Web of Science ID 000308631200007

    View details for PubMedID 22909017

    View details for PubMedCentralID PMC3475495

  • Excitation transfer induced spectral diffusion and the influence of structural spectral diffusion JOURNAL OF CHEMICAL PHYSICS Rosenfeld, D. E., Fayer, M. D. 2012; 137 (6)

    Abstract

    The theory of vibrational excitation transfer, which causes spectral diffusion and is also influenced by structural spectral diffusion, is developed and applied to systems consisting of vibrational chromophores. Excitation transfer induced spectral diffusion is the time-dependent change in vibrational frequency induced by an excitation on an initially excited molecule jumping to other molecules that have different vibrational frequencies within the inhomogeneously broadened vibrational absorption line. The excitation transfer process is modeled as Förster resonant transfer, which depends on the overlap of the homogeneous spectra of the donating and accepting vibrational chromophores. Because the absorption line is inhomogeneously broadened, two molecules in close proximity can have overlaps of their homogeneous lines that range from substantial to very little. In the absence of structural dynamics, the overlap of the homogeneous lines of the donating and accepting vibrational chromophores would be fixed. However, dynamics of the medium that contains the vibrational chromophores, e.g., a liquid solvent or a surrounding protein, produce spectral diffusion. Spectral diffusion causes the position of a molecule's homogeneous line within the inhomogeneous spectrum to change with time. Therefore, the overlap of donating and accepting molecules' homogeneous lines is time dependent, which must be taken into account in the excitation transfer theory. The excitation transfer problem is solved for inhomogeneous lines with fluctuating homogeneous line frequencies. The method allows the simultaneous treatment of both excitation transfer induced spectral diffusion and structural fluctuation induced spectral diffusion. It is found that the excitation transfer process is enhanced by the stochastic fluctuations in frequencies. It is shown how a measurement of spectral diffusion can be separated into the two types of spectral diffusion, which permits the structural spectral diffusion to be determined in the presence of excitation transfer spectral diffusion. Various approximations and computational methodologies are explored.

    View details for DOI 10.1063/1.4742762

    View details for Web of Science ID 000308048700009

    View details for PubMedID 22897257

  • Conformational Dynamics and Stability of HP35 Studied with 2D IR Vibrational Echoes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chung, J. K., Thielges, M. C., Fayer, M. D. 2012; 134 (29): 12118-12124

    Abstract

    Two-dimensional infrared (2D IR) vibrational echo spectroscopy was used to measure the fast dynamics of two variants of chicken villin headpiece 35 (HP35). The CN of cyanophenylalanine residues inserted in the hydrophobic core were used as a vibrational probe. Experiments were performed on both singly (HP35-P) and doubly CN-labeled peptide (HP35-P(2)) within the wild-type sequence, as well as on HP-35 containing a singly labeled cyanophenylalanine and two norleucine mutations (HP35-P NleNle). There is a remarkable similarity between the dynamics measured in singly and doubly CN-labeled HP35, demonstrating that the presence of an additional CN vibrational probe does not significantly alter the dynamics of the small peptide. The substitution of two lysine residues by norleucines markedly improves the stability of HP35 by replacing charged with nonpolar residues, stabilizing the hydrophobic core. The results of the 2D IR experiments reveal that the dynamics of HP35-P are significantly faster than those of HP35-P NleNle. These observations suggest that the slower structural fluctuations in the hydrophobic core, indicating a more tightly structured core, may be an important contributing factor to HP35-P NleNle's increased stability.

    View details for DOI 10.1021/ja303017d

    View details for Web of Science ID 000306724500059

    View details for PubMedID 22764745

    View details for PubMedCentralID PMC3487692

  • Water Dynamics in Water/DMSO Binary Mixtures JOURNAL OF PHYSICAL CHEMISTRY B Wong, D. B., Sokolowsky, K. P., El-Barghouthi, M. I., Fenn, E. E., Giammanco, C. H., Sturlaugson, A. L., Fayer, M. D. 2012; 116 (18): 5479-5490

    Abstract

    The dynamics of dimethyl sulfoxide (DMSO)/water solutions with a wide range of water concentrations are studied using polarization selective infrared pump-probe experiments, two-dimensional infrared (2D IR) vibrational echo spectroscopy, optical heterodyne detected optical Kerr effect (OHD-OKE) experiments, and IR absorption spectroscopy. Vibrational population relaxation of the OD stretch of dilute HOD in H(2)O displays two vibrational lifetimes even at very low water concentrations that are associated with water-water and water-DMSO hydrogen bonds. The IR absorption spectra also show characteristics of both water-DMSO and water-water hydrogen bonding. Although two populations are observed, water anisotropy decays (orientational relaxation) exhibit single ensemble behavior, indicative of concerted reorientation involving water and DMSO molecules. OHD-OKE experiments, which measure the orientational relaxation of DMSO, reveal that the DMSO orientational relaxation times are the same as orientational relaxation times found for water over a wide range of water concentrations within experimental error. The fact that the reorientation times of water and DMSO are basically the same shows that the reorientation of water is coupled to the reorientation of DMSO itself. These observations are discussed in terms of a jump reorientation model. Frequency-frequency correlation functions determined from the 2D IR experiments on the OD stretch show both fast and slow spectral diffusion. In analogy to bulk water, the fast component is assigned to very local hydrogen bond fluctuations. The slow component, which is similar to the slow water reorientation time at each water concentration, is associated with global hydrogen bond structural randomization.

    View details for DOI 10.1021/jp301967e

    View details for Web of Science ID 000303786500017

    View details for PubMedID 22510039

  • Ribonuclease S Dynamics Measured Using a Nitrile Label with 2D IR Vibrational Echo Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Bagchi, S., Boxer, S. G., Fayer, M. D. 2012; 116 (13): 4034-4042

    Abstract

    A nitrile-labeled amino acid, p-cyanophenylalanine, is introduced near the active site of the semisynthetic enzyme ribonuclease S to serve as a probe of protein dynamics and fluctuations. Ribonuclease S is the limited proteolysis product of subtilisin acting on ribonuclease A, and consists of a small fragment including amino acids 1-20, the S-peptide, and a larger fragment including residues 21-124, the S-protein. A series of two-dimensional vibrational echo experiments performed on the nitrile-labeled S-peptide and the RNase S are described. The time-dependent changes in the two-dimensional infrared vibrational echo line shapes are analyzed using the center line slope method to obtain the frequency-frequency correlation function (FFCF). The observations show that the nitrile probe in the S-peptide has dynamics that are similar to, but faster than, those of the single amino acid p-cyanophenylalanine in water. In contrast, the dynamics of the nitrile label when the peptide is bound to form ribonuclease S are dominated by homogeneous dephasing (motionally narrowed) contributions with only a small contribution from very fast inhomogeneous structural dynamics. The results provide insights into the nature of the structural dynamics of the ribonuclease S complex. The equilibrium dynamics of the nitrile labeled S-peptide and the ribonuclease S complex are also investigated by molecular dynamics simulations. The experimentally determined FFCFs are compared to the FFCFs obtained from the molecular dynamics simulations, thereby testing the capacity of simulations to determine the amplitudes and time scales of protein structural fluctuations on fast time scales under thermal equilibrium conditions.

    View details for DOI 10.1021/jp2122856

    View details for Web of Science ID 000302337000015

    View details for PubMedID 22417088

    View details for PubMedCentralID PMC3354990

  • Investigation of Nanostructure in Room Temperature Ionic Liquids using Electronic Excitation Transfer JOURNAL OF PHYSICAL CHEMISTRY B Fruchey, K., Lawler, C. M., Fayer, M. D. 2012; 116 (10): 3054-3064

    Abstract

    Donor-donor electronic excitation transfer among 9-phenylanthracene (9PA) chromophores was measured in the room temperature ionic liquid (RTIL) 1-methyl-3-octylimidazolium chloride using time dependent fluorescence depolarization. 9PA, which is uncharged and nonpolar, will partition into the organic regions of the RTIL. The excitation transfer rate, which is sensitive to the distribution of chromophores in the RTIL, is modeled using different spatial configurations of 9PA molecules in the RTIL solution. The models are an isotropic distribution (random distribution) and a clustered sphere model to represent hydrophobic regions of a nanostructured environment. Model calculations were performed to demonstrate the sensitivity of excitation transfer to different distributions of chromophores. When compared to the experiment, the isotropic model can adequately match the data. From a Bayesian analysis of the sensitivity of the excitation transfer to the models for the spatial distribution of chromophores, an upper limit of 6 Å radius is placed on the size of hydrophobic domains in the RTIL.

    View details for DOI 10.1021/jp207757r

    View details for Web of Science ID 000301509500002

    View details for PubMedID 22313385

  • Orientational Dynamics of Room Temperature Ionic Liquid/Water Mixtures: Water-Induced Structure JOURNAL OF PHYSICAL CHEMISTRY B Sturlaugson, A. L., Fruchey, K. S., Fayer, M. D. 2012; 116 (6): 1777-1787

    Abstract

    Optical heterodyne detected optical Kerr effect (OHD-OKE) measurements on a series of 1-alkyl-3-methylimidazolium tetrafluoroborate room-temperature ionic liquids (RTILs) as a function of chain length and water concentration are presented. The pure RTIL reorientational dynamics are identical in form to those of other molecular liquids studied previously by OHD-OKE (two power laws followed by a single exponential decay at long times), but are much slower at room temperature. In contrast, the addition of water to the longer alkyl chain RTILs causes the emergence of a long time biexponential orientational anisotropy decay. Such distinctly biexponential decays have not been seen previously in OHD-OKE experiments on any type of liquid and are analyzed here using a wobbling-in-a-cone model. The slow component for the longer chain RTILs does not obey the Debye-Stokes-Einstein (DSE) equation across the range of solutions, and thus we attribute it to slow cation reorientational diffusion caused by a stiffening of cation alkyl tail-tail associations. The fast component of the decay is assigned to the motions (wobbling) of the tethered imidazolium head groups. The wobbling-in-a-cone analysis provides estimates of the range of angles sampled by the imidazolium head group prior to the long time scale complete orientational randomization. The heterogeneous dynamics and non-DSE behavior observed here should have a significant effect on reaction rates in RTIL/water cosolvent mixtures.

    View details for DOI 10.1021/jp209942r

    View details for Web of Science ID 000300274900005

    View details for PubMedID 22224942

  • Dynamics of Water Interacting with Interfaces, Molecules, and Ions. ACCOUNTS OF CHEMICAL RESEARCH Fayer, M. D. 2012; 45 (1): 3-14

    Abstract

    Water is a critical component of many chemical processes, in fields as diverse as biology and geology. Water in chemical, biological, and other systems frequently occurs in very crowded situations: the confined water must interact with a variety of interfaces and molecular groups, often on a characteristic length scale of nanometers. Water's behavior in diverse environments is an important contributor to the functioning of chemical systems. In biology, water is found in cells, where it hydrates membranes and large biomolecules. In geology, interfacial water molecules can control ion adsorption and mineral dissolution. Embedded water molecules can change the structure of zeolites. In chemistry, water is an important polar solvent that is often in contact with interfaces, for example, in ion-exchange resin systems. Water is a very small molecule; its unusual properties for its size are attributable to the formation of extended hydrogen bond networks. A water molecule is similar in mass and volume to methane, but methane is a gas at room temperature, with melting and boiling points of 91 and 112 K, respectively. This is in contrast to water, with melting and boiling points of 273 and 373 K, respectively. The difference is that water forms up to four hydrogen bonds with approximately tetrahedral geometry. Water's hydrogen bond network is not static. Hydrogen bonds are constantly forming and breaking. In bulk water, the time scale for hydrogen bond randomization through concerted formation and dissociation of hydrogen bonds is approximately 2 ps. Water's rapid hydrogen bond rearrangement makes possible many of the processes that occur in water, such as protein folding and ion solvation. However, many processes involving water do not take place in pure bulk water, and water's hydrogen bond structural dynamics can be substantially influenced by the presence of, for example, interfaces, ions, and large molecules. In this Account, spectroscopic studies that have been used to explore the details of these influences are discussed. Because rearrangements of water molecules occur so quickly, ultrafast infrared experiments that probe water's hydroxyl stretching mode are useful in providing direct information about water dynamics on the appropriate time scales. Infrared polarization-selective pump-probe experiments and two-dimensional infrared (2D IR) vibrational echo experiments have been used to study the hydrogen bond dynamics of water. Water orientational relaxation, which requires hydrogen bond rearrangements, has been studied at spherical interfaces of ionic reverse micelles and compared with planar interfaces of lamellar structures composed of the same surfactants. Water orientational relaxation slows considerably at interfaces. It is found that the geometry of the interface is less important than the presence of the interface. The influence of ions is shown to slow hydrogen bond rearrangements. However, comparing an ionic interface to a neutral interface demonstrates that the chemical nature of the interface is less important than the presence of the interface. Finally, it is found that the dynamics of water at an organic interface is very similar to water molecules interacting with a large polyether.

    View details for DOI 10.1021/ar2000088

    View details for Web of Science ID 000301083400002

    View details for PubMedID 21417263

    View details for PubMedCentralID PMC3151308

  • Water in a Crowd PHYSIOLOGY Fayer, M. D. 2011; 26 (6): 381-392

    Abstract

    In many situations, form biology to geology, water occurs not as the pure bulk liquid but rather in nanoscopic environments, in contact with interfaces, interacting with ionic species, and interacting with large organic molecules. In such situations, water does not behave in the same manner as it does in the pure bulk liquid. Water dynamics are fundamental to many processes such as protein folding and proton transport. Such processes depend on the dynamics of water's hydrogen bonding network. Here, the results of ultrafast infrared experiments are described that shed light on the influences of nanoconfinement, interfaces, ions, and organic molecules on water hydrogen bond dynamics.

    View details for DOI 10.1152/physiol.00021.2011

    View details for Web of Science ID 000298377300002

    View details for PubMedID 22170957

  • Structural Dynamics of a Catalytic Monolayer Probed by Ultrafast 2D IR Vibrational Echoes SCIENCE Rosenfeld, D. E., Gengeliczki, Z., Smith, B. J., Stack, T. D., Fayer, M. D. 2011; 334 (6056): 634-639

    Abstract

    Ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy has proven broadly useful for studying molecular dynamics in solutions. Here, we extend the technique to probing the interfacial dynamics and structure of a silica surface-tethered transition metal carbonyl complex--tricarbonyl (1,10-phenanthroline)rhenium chloride--of interest as a photoreduction catalyst. We interpret the data using a theoretical framework devised to separate the roles of structural evolution and excitation transfer in inducing spectral diffusion. The structural dynamics, as reported on by a carbonyl stretch vibration of the surface-bound complex, have a characteristic time of ~150 picoseconds in the absence of solvent, decrease in duration by a factor of three upon addition of chloroform, and decrease another order of magnitude for the bulk solution. Conversely, solvent-complex interactions increase the lifetime of the probed vibration by 160% when solvent is applied to the monolayer.

    View details for DOI 10.1126/science.1211350

    View details for Web of Science ID 000296494700045

    View details for PubMedID 22021674

  • Dynamics of Water at the Interface in Reverse Micelles: Measurements of Spectral Diffusion with Two-Dimensional Infrared Vibrational Echoes JOURNAL OF PHYSICAL CHEMISTRY B Fenn, E. E., Wong, D. B., Giammanco, C. H., Fayer, M. D. 2011; 115 (40): 11658-11670

    Abstract

    Water dynamics inside of reverse micelles made from the surfactant Aerosol-OT (AOT) were investigated by observing spectral diffusion, orientational relaxation, and population relaxation using two-dimensional infrared (2D IR) vibrational echo spectroscopy and pump-probe experiments. The water pool sizes of the reverse micelles studied ranged in size from 5.8 to 1.7 nm in diameter. It is found that spectral diffusion, characterized by the frequency-frequency correlation function (FFCF), significantly changes as the water pool size decreases. For the larger reverse micelles (diameter 4.6 nm and larger), the 2D IR signal is composed of two spectral components: a signal from bulk-like core water, and a signal from water at the headgroup interface. Each of these signals (core water and interfacial water) is associated with a distinct FFCF. The FFCF of the interfacial water layer can be obtained using a modified center line slope (CLS) method that has been recently developed. The interfacial FFCFs for large reverse micelles have a single exponential decay (∼1.6 ps) to an offset plus a fast homogeneous component and are nearly identical for all large sizes. The observed ∼1.6 ps interfacial decay component is approximately the same as that found for bulk water and may reflect hydrogen bond rearrangement of bulk-like water molecules hydrogen bonded to the interfacial water molecules. The long time offset arises from dynamics that are too slow to be measured on the accessible experimental time scale. The influence of the chemical nature of the interface on spectral diffusion was explored by comparing data for water inside reverse micelles (5.8 nm water pool diameter) made from the surfactants AOT and Igepal CO-520. AOT has charged, sulfonate head groups, while Igepal CO-520 has neutral, hydroxyl head groups. It is found that spectral diffusion on the observable time scales is not overly sensitive to the chemical makeup of the interface. An intermediate-sized AOT reverse micelle (water pool diameter of 3.3 nm) is analyzed as a large reverse micelle because it has distinct core and interface regions, but its core region is more constrained than bulk water. The interfacial FFCF for this intermediate-sized reverse micelle is somewhat slower than those found for the larger reverse micelles. The water nanopools in the smaller reverse micelles cannot be separated into core and interface regions. In the small reverse micelles, the FFCFs are biexponential decays to an offset plus a fast homogeneous component. Each small reverse micelle exhibits an ∼1 ps decay time, which may arise from local hydrogen bond fluctuations and a slower, ∼6-10 ps decay, which is possibly due to slow hydrogen bond rearrangement of noninterfacial water molecules or topography fluctuations at the interface.

    View details for DOI 10.1021/jp206903k

    View details for Web of Science ID 000295545900014

    View details for PubMedID 21899355

  • Two-Dimensional IR Spectroscopy of Protein Dynamics Using Two Vibrational Labels: A Site-Specific Genetically Encoded Unnatural Amino Acid and an Active Site Ligand JOURNAL OF PHYSICAL CHEMISTRY B Thielges, M. C., Axup, J. Y., Wong, D., Lee, H. S., Chung, J. K., Schultz, P. G., Fayer, M. D. 2011; 115 (38): 11294-11304

    Abstract

    Protein dynamics and interactions in myoglobin (Mb) were characterized via two vibrational dynamics labels (VDLs): a genetically incorporated site-specific azide (Az) bearing unnatural amino acid (AzPhe43) and an active site CO ligand. The Az-labeled protein was studied using ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy. CO bound at the active site of the heme serves as a second VDL located nearby. Therefore, it was possible to use Fourier transform infrared (FT-IR) and 2D IR spectroscopic experiments on the Az in unligated Mb and in Mb bound to CO (MbAzCO) and on the CO in MbCO and MbAzCO to investigate the environment and motions of different states of one protein from the perspective of two spectrally resolved VDLs. A very broad bandwidth 2D IR spectrum, encompassing both the Az and CO spectral regions, found no evidence of direct coupling between the two VDLs. In MbAzCO, both VDLs reported similar time scale motions: very fast homogeneous dynamics, fast, ∼1 ps dynamics, and dynamics on a much slower time scale. Therefore, each VDL reports independently on the protein dynamics and interactions, and the measured dynamics are reflective of the protein motions rather than intrinsic to the chemical nature of the VDL. The AzPhe VDL also permitted study of oxidized Mb dynamics, which could not be accessed previously with 2D IR spectroscopy. The experiments demonstrate that the combined application of 2D IR spectroscopy and site-specific incorporation of VDLs can provide information on dynamics, structure, and interactions at virtually any site throughout any protein.

    View details for DOI 10.1021/jp206986v

    View details for Web of Science ID 000295057900029

    View details for PubMedID 21823631

    View details for PubMedCentralID PMC3261801

  • Time-Dependent Fifth-Order Bands in Nominally Third-Order 2D IR Vibrational Echo Spectra JOURNAL OF PHYSICAL CHEMISTRY A Thielges, M. C., Fayer, M. D. 2011; 115 (34): 9714-9723

    Abstract

    Progress in the field of 2D IR vibrational spectroscopy has been bolstered by the production of intense mid-IR laser pulses. As higher-energy pulses are employed, a concomitant increase occurs in the likelihood of fifth-order contributions to the 2D IR spectra. We report the appearance of fifth-order signals in 2D IR spectra of CO bound to the active site of the enzyme cytochrome P450(cam) with the substrate norcamphor. Two bands with novel time dependences, one on the diagonal and one off-diagonal, are not accounted for by normal third-order interactions. These bands are associated with a ν = 1-2 vibrational transition frequency. Both bands decay to 0 and then grow back in with opposite sign. The diagonal band is positive at short time, decays to 0, reappears with negative sign, before eventually decaying to 0. The off-diagonal band is negative at short time, decays to 0, reappears positive, and then decays to 0. The appearance and time dependence of these bands are characterized. Understanding these fifth-order bands is useful because they may be misidentified with time-dependent bands that arise from other processes, such as chemical exchange, vibrational coupling, or energy transfer. The presence and unusual time dependences of the fifth-order bands are reproduced with model calculations that account for the fact that vibrational relaxation from the ν = 2 to 1 level is approximately a factor of 2 faster than that from the ν = 1 to 0 level.

    View details for DOI 10.1021/jp201516s

    View details for Web of Science ID 000294146400046

    View details for PubMedID 21648438

    View details for PubMedCentralID PMC3162047

  • Extracting 2D IR frequency-frequency correlation functions from two component systems JOURNAL OF CHEMICAL PHYSICS Fenn, E. E., Fayer, M. D. 2011; 135 (7)

    Abstract

    The center line slope (CLS) method is often used to extract the frequency-frequency correlation function (FFCF) from 2D IR spectra to delineate dynamics and to identify homogeneous and inhomogeneous contributions to the absorption line shape of a system. While the CLS method is extremely efficient, quite accurate, and immune to many experimental artifacts, it has only been developed and properly applied to systems that have a single vibrational band, or to systems of two species that have spectrally resolved absorption bands. In many cases, the constituent spectra of multiple component systems overlap and cannot be distinguished from each other. This situation creates ambiguity when analyzing 2D IR spectra because dynamics for different species cannot be separated. Here a mathematical formulation is presented that extends the CLS method for a system consisting of two components (chemically distinct uncoupled oscillators). In a single component system, the CLS corresponds to the time-dependent portion of the normalized FFCF. This is not the case for a two component system, as a much more complicated expression arises. The CLS method yields a series of peak locations originating from slices taken through the 2D spectra. The slope through these peak locations yields the CLS value for the 2D spectra at a given T(w). We derive analytically that for two component systems, the peak location of the system can be decomposed into a weighted combination of the peak locations of the constituent spectra. The weighting depends upon the fractional contribution of each species at each wavelength and also on the vibrational lifetimes of both components. It is found that an unknown FFCF for one species can be determined as long as the peak locations (referred to as center line data) of one of the components are known, as well as the vibrational lifetimes, absorption spectra, and other spectral information for both components. This situation can arise when a second species is introduced into a well characterized single species system. An example is a system in which water exists in bulk form and also as water interacting with an interface. An algorithm is presented for back-calculating the unknown FFCF of the second component. The accuracy of the algorithm is tested with a variety of model cases in which all components are initially known. The algorithm successfully reproduces the FFCF for the second component within a reasonable degree of error.

    View details for DOI 10.1063/1.3625278

    View details for Web of Science ID 000294065200026

    View details for PubMedID 21861571

  • Influence of Histidine Tag Attachment on Picosecond Protein Dynamics BIOCHEMISTRY Thielges, M. C., Chung, J. K., Axup, J. Y., Fayer, M. D. 2011; 50 (25): 5799-5805

    Abstract

    Polyhistidine affinity tags are routinely employed as a convenient means of purifying recombinantly expressed proteins. A tacit assumption is commonly made that His tags have little influence on protein structure and function. Attachment of a His tag to the N-terminus of the robust globular protein myoglobin leads to only minor changes to the electrostatic environment of the heme pocket, as evinced by the nearly unchanged Fourier transform infrared spectrum of CO bound to the heme of His-tagged myoglobin. Experiments employing two-dimensional infrared vibrational echo spectroscopy of the heme-bound CO, however, find that significant changes occur to the short time scale (picoseconds) dynamics of myoglobin as a result of His tag incorporation. The His tag mainly reduces the dynamics on the 1.4 ps time scale and also alters protein motions of myoglobin on the slower, >100 ps time scale, as demonstrated by the His tag's influence on the fluctuations of the CO vibrational frequency, which reports on protein structural dynamics. The results suggest that affinity tags may have effects on protein function and indicate that investigators of affinity-tagged proteins should take this into consideration when investigating the dynamics and other properties of such proteins.

    View details for DOI 10.1021/bi2003923

    View details for Web of Science ID 000291897000023

    View details for PubMedID 21619030

    View details for PubMedCentralID PMC3133630

  • Temperature Dependent Equilibrium Native to Unfolded Protein Dynamics and Properties Observed with IR Absorption and 2D IR Vibrational Echo Experiments JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chung, J. K., Thielges, M. C., Bowman, S. E., Bren, K. L., Fayer, M. D. 2011; 133 (17): 6681-6691

    Abstract

    Dynamic and structural properties of carbonmonoxy (CO)-coordinated cytochrome c(552) from Hydrogenobacter thermophilus (Ht-M61A) at different temperatures under thermal equilibrium conditions were studied with infrared absorption spectroscopy and ultrafast two-dimensional infrared (2D IR) vibrational echo experiments using the heme-bound CO as the vibrational probe. Depending on the temperature, the stretching mode of CO shows two distinct bands corresponding to the native and unfolded proteins. As the temperature is increased from low temperature, a new absorption band for the unfolded protein grows in and the native band decreases in amplitude. Both the temperature-dependent circular dichroism and the IR absorption area ratio R(A)(T), defined as the ratio of the area under the unfolded band to the sum of the areas of the native and unfolded bands, suggest a two-state transition from the native to the unfolded protein. However, it is found that the absorption spectrum of the unfolded protein increases its inhomogeneous line width and the center frequency shifts as the temperature is increased. The changes in line width and center frequency demonstrate that the unfolding does not follow simple two-state behavior. The temperature-dependent 2D IR vibrational echo experiments show that the fast dynamics of the native protein are virtually temperature independent. In contrast, the fast dynamics of the unfolded protein are slower than those of the native protein, and the unfolded protein fast dynamics and at least a portion of the slower dynamics of the unfolded protein change significantly, becoming faster as the temperature is raised. The temperature dependence of the absorption spectrum and the changes in dynamics measured with the 2D IR experiments confirm that the unfolded ensemble of conformers continuously changes its nature as unfolding proceeds, in contrast to the native state, which displays a temperature-independent distribution of structures.

    View details for DOI 10.1021/ja111009s

    View details for Web of Science ID 000290363400036

    View details for PubMedID 21469666

  • Protein Dynamics in Cytochrome P450 Molecular Recognition and Substrate Specificity Using 2D IR Vibrational Echo Spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Thielges, M. C., Chung, J. K., Fayer, M. D. 2011; 133 (11): 3995-4004

    Abstract

    Cytochrome (cyt) P450s hydroxylate a variety of substrates that can differ widely in their chemical structure. The importance of these enzymes in drug metabolism and other biological processes has motivated the study of the factors that enable their activity on diverse classes of molecules. Protein dynamics have been implicated in cyt P450 substrate specificity. Here, 2D IR vibrational echo spectroscopy is employed to measure the dynamics of cyt P450(cam) from Pseudomonas putida on fast time scales using CO bound at the active site as a vibrational probe. The substrate-free enzyme and the enzyme bound to both its natural substrate, camphor, and a series of related substrates are investigated to explicate the role of dynamics in molecular recognition in cyt P450(cam) and to delineate how the motions may contribute to hydroxylation specificity. In substrate-free cyt P450(cam), three conformational states are populated, and the structural fluctuations within a conformational state are relatively slow. Substrate binding selectively stabilizes one conformational state, and the dynamics become faster. Correlations in the observed dynamics with the specificity of hydroxylation of the substrates, the binding affinity, and the substrates' molecular volume suggest that motions on the hundreds of picosecond time scale contribute to the variation in activity of cyt P450(cam) toward different substrates.

    View details for DOI 10.1021/ja109168h

    View details for Web of Science ID 000288889900058

    View details for PubMedID 21348488

    View details for PubMedCentralID PMC3063108

  • Dynamics of the folded and unfolded villin headpiece (HP35) measured with ultrafast 2D IR vibrational echo spectroscopy PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Chung, J. K., Thielges, M. C., Fayer, M. D. 2011; 108 (9): 3578-3583

    Abstract

    A series of two-dimensional infrared vibrational echo experiments performed on nitrile-labeled villin headpiece [HP35-(CN)(2)] is described. HP35 is a small peptide composed of three alpha helices in the folded configuration. The dynamics of the folded HP35-(CN)(2) are compared to that of the guanidine-induced unfolded peptide, as well as the nitrile-functionalized phenylalanine (PheCN), which is used to differentiate the peptide dynamic contributions to the observables from those of the water solvent. Because the viscosity of solvent has a significant effect on fast dynamics, the viscosity of the solvent is held constant by adding glycerol. For the folded peptide, the addition of glycerol to the water solvent causes observable slowing of the peptide's dynamics. Holding the viscosity constant as GuHCl is added, the dynamics of unfolded peptide are much faster than those of the folded peptide, and they are very similar to that of PheCN. These observations indicate that the local environment of the nitrile in the unfolded peptide resembles that of PheCN, and the dynamics probed by the CN are dominated by the fluctuations of the solvent molecules, in contrast to the observations on the folded peptide.

    View details for DOI 10.1073/pnas.1100587108

    View details for Web of Science ID 000287844400029

    View details for PubMedID 21321226

    View details for PubMedCentralID PMC3048147

  • Temperature and Hydration-Dependent Rotational and Translational Dynamics of a Polyether Oligomer JOURNAL OF PHYSICAL CHEMISTRY B Sturlaugson, A. L., Fayer, M. D. 2011; 115 (5): 945-950

    Abstract

    Temperature-dependent rotational diffusion of tetraethylene glycol dimethyl ether (TEGDE) is measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy and compared to previous measurements of rotational diffusion as a function of water content. Both types of data, temperature-dependent and hydration-dependent, follow the Debye-Stokes-Einstein (DSE) equation and agree quantitatively with hydrodynamic calculations. Of particular importance is the result that both types of data show nearly identical dependence on the viscosity divided by the temperature (η/T). We also compare the translational diffusion constants as previously measured by pulsed field gradient spin-echo (PFG-SE) NMR as a function of both temperature and water content. The temperature-dependent data follow the Stokes-Einstein (SE) equation. Similar to the rotation, the low water content mixtures obey the SE equation and show the same proportionality to η/T as the temperature-dependent data. At higher water fractions, the data do not obey the SE equation. The principal results are that the influence of temperature on dry TEGDE orientational relaxation is the same as the influence of water content at fixed temperature, and that the influence of temperature on translational diffusion of dry TEGDE is the same as the influence of water content over a range of relatively low water concentrations. The results demonstrate that there are no large TEGDE structural changes or specific, long-lived water-polyether interactions in the solutions over the entire concentration range.

    View details for DOI 10.1021/jp110487j

    View details for Web of Science ID 000286797700020

    View details for PubMedID 21222441

  • Water dynamics in small reverse micelles in two solvents: Two-dimensional infrared vibrational echoes with two-dimensional background subtraction JOURNAL OF CHEMICAL PHYSICS Fenn, E. E., Wong, D. B., Fayer, M. D. 2011; 134 (5)

    Abstract

    Water dynamics as reflected by the spectral diffusion of the water hydroxyl stretch were measured in w(0) = 2 (1.7 nm diameter) Aerosol-OT (AOT)/water reverse micelles in carbon tetrachloride and in isooctane solvents using ultrafast 2D IR vibrational echo spectroscopy. Orientational relaxation and population relaxation are observed for w(0) = 2, 4, and 7.5 in both solvents using IR pump-probe measurements. It is found that the pump-probe observables are sensitive to w(0), but not to the solvent. However, initial analysis of the vibrational echo data from the water nanopool in the reverse micelles in the isooctane solvent seems to yield different dynamics than the CCl(4) system in spite of the fact that the spectra, vibrational lifetimes, and orientational relaxation are the same in the two systems. It is found that there are beat patterns in the interferograms with isooctane as the solvent. The beats are observed from a signal generated by the AOT/isooctane system even when there is no water in the system. A beat subtraction data processing procedure does a reasonable job of removing the distortions in the isooctane data, showing that the reverse micelle dynamics are the same within experimental error regardless of whether isooctane or carbon tetrachloride is used as the organic phase. Two time scales are observed in the vibrational echo data, ~1 and ~10 ps. The slower component contains a significant amount of the total inhomogeneous broadening. Physical arguments indicate that there is a much slower component of spectral diffusion that is too slow to observe within the experimental window, which is limited by the OD stretch vibrational lifetime.

    View details for DOI 10.1063/1.3532542

    View details for Web of Science ID 000287095500059

    View details for PubMedID 21303143

  • Water Dynamics in Small AOT Reverse Micelles in Two Solvents: 2D IR Vibrational Echoes with 2D Background Subtraction J. Chem. Phys. Fenn, E. E., Wong, D. B., Fayer, M. D. 2011; 134 (054512)
  • The Influence of Histidine Tag Attachment on Protein Dynamics Biochemistry Thielges, M. C., Chung, J. K., Axup, J. Y., Fayer, M. D. 2011; 50: 5799-5805
  • Time-Dependent 5th Order Bands in Nominally 3rd Order 2D IR Vibrational Echo Spectra J. Phys. Chem. A Thielges, M. C., Fayer, M. D. 2011; 115: 9714-9723
  • Conformational Switching between Protein Substates Studied with 2D IR Vibrational Echo Spectroscopy and Molecular Dynamics Simulations JOURNAL OF PHYSICAL CHEMISTRY B Bagchi, S., Thorpe, D. G., Thorpe, I. F., Voth, G. A., Fayer, M. D. 2010; 114 (51): 17187-17193

    Abstract

    Myoglobin is an important protein for the study of structure and dynamics. Three conformational substates have been identified for the carbonmonoxy form of myoglobin (MbCO). These are manifested as distinct peaks in the IR absorption spectrum of the CO stretching mode. Ultrafast 2D IR vibrational echo chemical exchange experiments are used to observed switching between two of these substates, A(1) and A(3), on a time scale of <100 ps for two mutants of wild-type Mb. The two mutants are a single mutation of Mb, L29I, and a double mutation, T67R/S92D. Molecular dynamics (MD) simulations are used to model the structural differences between the substates of the two MbCO mutants. The MD simulations are also employed to examine the substate switching in the two mutants as a test of the ability of MD simulations to predict protein dynamics correctly for a system in which there is a well-defined transition over a significant potential barrier between two substates. For one mutant, L29I, the simulations show that translation of the His64 backbone may differentiate the two substates. The simulations accurately reproduce the experimentally observed interconversion time for the L29I mutant. However, MD simulations exploring the same His64 backbone coordinate fail to display substate interconversion for the other mutant, T67R/S92D, thus pointing to the likely complexity of the underlying protein interactions. We anticipate that understanding conformational dynamics in MbCO via ultrafast 2D IR vibrational echo chemical exchange experiments can help to elucidate fast conformational switching processes in other proteins.

    View details for DOI 10.1021/jp109203b

    View details for Web of Science ID 000285560100022

    View details for PubMedID 21128650

  • Dynamics of a Myoglobin Mutant Enzyme: 2D IR Vibrational Echo Experiments and Simulations JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Bagchi, S., Nebgen, B. T., Loring, R. F., Fayer, M. D. 2010; 132 (51): 18367-18376

    Abstract

    Myoglobin (Mb) double mutant T67R/S92D displays peroxidase enzymatic activity in contrast to the wild type protein. The CO adduct of T67R/S92D shows two CO absorption bands corresponding to the A(1) and A(3) substates. The equilibrium protein dynamics for the two distinct substates of the Mb double mutant are investigated by using two-dimensional infrared (2D IR) vibrational echo spectroscopy and molecular dynamics (MD) simulations. The time-dependent changes in the 2D IR vibrational echo line shapes for both of the substates are analyzed using the center line slope (CLS) method to obtain the frequency-frequency correlation function (FFCF). The results for the double mutant are compared to those from the wild type Mb. The experimentally determined FFCF is compared to the FFCF obtained from molecular dynamics simulations, thereby testing the capacity of a force field to determine the amplitudes and time scales of protein structural fluctuations on fast time scales. The results provide insights into the nature of the energy landscape around the free energy minimum of the folded protein structure.

    View details for DOI 10.1021/ja108491t

    View details for Web of Science ID 000285818700056

    View details for PubMedID 21142083

  • Room Temperature Ionic Liquid-Lithium Salt Mixtures: Optical Kerr Effect Dynamical Measurements JOURNAL OF PHYSICAL CHEMISTRY B Nicolau, B. G., Sturlaugson, A., Fruchey, K., Ribeiro, M. C., Fayer, M. D. 2010; 114 (25): 8350-8356

    Abstract

    The addition of lithium salts to ionic liquids causes an increase in viscosity and a decrease in ionic mobility that hinders their possible application as an alternative solvent in lithium ion batteries. Optically heterodyne-detected optical Kerr effect spectroscopy was used to study the change in dynamics, principally orientational relaxation, caused by the addition of lithium bis(trifluoromethylsulfonyl)imide to the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Over the time scales studied (1 ps-16 ns) for the pure ionic liquid, two temperature-independent power laws were observed: the intermediate power law (1 ps to approximately 1 ns), followed by the von Schweidler power law. The von Schweidler power law is followed by the final complete exponential relaxation, which is highly sensitive to temperature. The lithium salt concentration, however, was found to affect both power laws, and a discontinuity could be found in the trend observed for the intermediate power law when the concentration (mole fraction) of lithium salt is close to chi(LiTf(2)N) = 0.2. A mode coupling theory (MCT) schematic model was also used to fit the data for both the pure ionic liquid and the different salt concentration mixtures. It was found that dynamics in both types of liquids are described very well by MCT.

    View details for DOI 10.1021/jp103810r

    View details for Web of Science ID 000278982200008

    View details for PubMedID 20527943

  • Theory of interfacial orientational relaxation spectroscopic observables JOURNAL OF CHEMICAL PHYSICS Gengeliczki, Z., Rosenfeld, D. E., Fayer, M. D. 2010; 132 (24)

    Abstract

    The orientational correlation functions measured in the time-resolved second-harmonic generation (TRSHG) and time-resolved sum-frequency generation (TRSFG) experiments are derived. In the laboratory coordinate system, the Y(l) (m)(Omega(lab)(t))Y(2) (m)(Omega(lab)(0)) (l=1,3 and m=0,2) correlation functions, where the Y(l) (m) are spherical harmonics, describe the orientational relaxation observables of molecules at interfaces. A wobbling-in-a-cone model is used to evaluate the correlation functions. The theory demonstrates that the orientational relaxation diffusion constant is not directly obtained from an experimental decay time in contrast to the situation for a bulk liquid. Model calculations of the correlation functions are presented to demonstrate how the diffusion constant and cone half-angle affect the time-dependence of the signals in TRSHG and TRSFG experiments. Calculations for the TRSHG experiments on Coumarin C314 molecules at air-water and air-water-surfactant interfaces are presented and used to examine the implications of published experimental results for these systems.

    View details for DOI 10.1063/1.3442446

    View details for Web of Science ID 000279740200041

    View details for PubMedID 20590210

  • Orientational and Translational Dynamics of Polyether/Water Solutions JOURNAL OF PHYSICAL CHEMISTRY B Sturlaugson, A. L., Fruchey, K. S., Lynch, S. R., Aragon, S. R., Fayer, M. D. 2010; 114 (16): 5350-5358

    Abstract

    Optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments and pulsed field-gradient spin-echo NMR (PFGSE-NMR) experiments were performed to measure the rotational and translational diffusion constants of a polyether, tetraethylene glycol dimethyl ether (TEGDE), in binary mixtures with water over concentrations ranging from pure TEGDE to approaching infinite dilution. In addition, hydrodynamic calculations of the rotational and translational diffusion constants for several rigid TEGDE conformations in the neat liquid and in the infinitely dilute solution were performed to supplement the experimental data. The rotational relaxation data follow the Debye-Stokes-Einstein (DSE) equation within experimental error over the entire water concentration range. The agreement with the DSE equation indicates that there is no significant structural change of the polyether as the water content is changed. In contrast to the rotational dynamics, the translational diffusion data show a distinct deviation from Stokes-Einstein (SE) behavior. As the water content of the mixture is reduced, the translational diffusion rate decreases less rapidly than the increase in viscosity alone predicts until the water/TEGDE mole ratio of 7:1 is reached. Upon further reduction of water content, the translational diffusion tracks the viscosity. Comparison of the translational data with the rotational data and the hydrodynamic computations shows that the translational dynamics cannot be explained by a molecular shape change and that the low water fraction solutions are the ones that deviate from hydrodynamic behavior. A conjecture is presented as a possible explanation for the different behaviors of the rotational and translational dynamics.

    View details for DOI 10.1021/jp101369e

    View details for Web of Science ID 000276889100018

    View details for PubMedID 20373773

  • Dynamics in Organic Ionic Liquids in Distinct Regions Using Charged and Uncharged Orientational Relaxation Probes JOURNAL OF PHYSICAL CHEMISTRY B Fruchey, K., Fayer, M. D. 2010; 114 (8): 2840-2845

    Abstract

    The temperature-dependent fluorescence anisotropy decay (orientational relaxation) of perylene and sodium 8-methoxypyrene-1,3,6-sulfonate (MPTS) were measured in a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (alkyl = ethyl, butyl, hexyl, octyl) organic room temperature ionic liquids (RTIL). The two fluorescent probe molecules display markedly different rotational dynamics when analyzed using Stokes-Einstein-Debye theory, demonstrating that they are located in distinct environments within the RTILs and have very different interactions with their surroundings. Perylene rotates with subslip behavior, becoming increasingly subslip as the length of ionic liquid alkyl chain is increased. The dynamics approach those of perylene in an organic oil. In contrast, MPTS shows superstick behavior, likely reflecting very strong coordination with the RTIL cations. These results are consistent with different elements of rotational friction within the ionic liquid structure, which are available to solutes depending on their chemical functionality.

    View details for DOI 10.1021/jp911123v

    View details for Web of Science ID 000274842600036

    View details for PubMedID 20136068

  • Hydrogen Bond Migration between Molecular Sites Observed with Ultrafast 2D IR Chemical Exchange Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Rosenfeld, D. E., Kwak, K., Gengeliczki, Z., Fayer, M. D. 2010; 114 (7): 2383-2389

    Abstract

    Hydrogen-bonded complexes between phenol and phenylacetylene are studied using ultrafast two-dimensional infrared (2D IR) chemical exchange spectroscopy. Phenylacetylene has two possible pi hydrogen bonding acceptor sites (phenyl or acetylene) that compete for hydrogen bond donors in solution at room temperature. The OD stretch frequency of deuterated phenol is sensitive to which acceptor site it is bound. The appearance of off-diagonal peaks between the two vibrational frequencies in the 2D IR spectrum reports on the exchange process between the two competitive hydrogen-bonding sites of phenol-phenylacetylene complexes in the neat phenylacetylene solvent. The chemical exchange process occurs in approximately 5 ps and is assigned to direct hydrogen bond migration along the phenylacetylene molecule. Other nonmigration mechanisms are ruled out by performing 2D IR experiments on phenol dissolved in the phenylacetylene/carbon tetrachloride mixed solvent. The observation of direct hydrogen bond migration can have implications for macromolecular systems.

    View details for DOI 10.1021/jp911452z

    View details for Web of Science ID 000274578500008

    View details for PubMedID 20121275

  • Absolutely Small - How Quantum Theory Explains Our Everyday World Fayer, M. D. AMACOM, New York. 2010
  • Solvent Control of the Soft Angular Potential in Hydroxyl-pi Hydrogen Bonds: Inertial Orientational Dynamics JOURNAL OF PHYSICAL CHEMISTRY B Rosenfeld, D. E., Gengeliczki, Z., Fayer, M. D. 2009; 113 (40): 13300-13307

    Abstract

    Ultrafast polarization and wavelength selective IR pump-probe spectroscopy is used to measure the inertial and long time orientational dynamics of pi-hydrogen bonding complexes. Inertial orientational relaxation is sensitive to the angular potential associated with the hydrogen bond. The complexes studied are composed of phenol-OD (hydroxyl hydrogen replaced by deuterium) and various pi-base solvents with different electron donating or withdrawing substituents (chlorobenzene, bromobenzene, benzene, toluene, p-xylene, mesitylene, 1-pentyne). The different substituents provide experimental control of the hydrogen bond strength. The inertial orientational relaxation of the complexes, measured at the center frequency of each line, is independent of the hydrogen bond strength, demonstrating the insensitivity of the OD inertial dynamics, and therefore the H-bond angular potential, to the hydrogen bond strength. OD stretch absorption bands are inhomogeneously broadened through interactions with the solvent. The hydrogen bonding complexes all have similar wavelength dependent inertial orientational relaxation across their inhomogeneously broadened OD stretch absorption lines. The wavelength dependence of the inertial reorientation across each line arises because of a correlation between local solvent structure and the angular potential. These two results imply that local solvent structure acts as the controlling influence in determining the extent of inertial orientational relaxation, and therefore the angular potential, and that variation in the pi-hydrogen bond strength is of secondary importance.

    View details for DOI 10.1021/jp907616x

    View details for Web of Science ID 000270363500023

    View details for PubMedID 19746960

  • Water dynamics at neutral and ionic interfaces PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Fenn, E. E., Wong, D. B., Fayer, M. D. 2009; 106 (36): 15243-15248

    Abstract

    The orientational dynamics of water at a neutral surfactant reverse micelle interface are measured with ultrafast infrared spectroscopy of the hydroxyl stretch, and the results are compared to orientational relaxation of water interacting with an ionic interface. The comparison provides insights into the influence of a neutral vs. ionic interface on hydrogen bond dynamics. Measurements are made and analyzed for large nonionic surfactant Igepal CO-520reverse micelles (water nanopool with a 9-nm diameter). The results are compared with those from a previous study of reverse micelles of the same size formed with the ionic surfactant Aerosol-OT (AOT). The results demonstrate that the orientational relaxation times for interfacial water molecules in the two types of reverse micelles are very similar (13 ps for Igepal and 18 ps for AOT) and are significantly slower than that of bulk water (2.6 ps). The comparison of water orientational relaxation at neutral and ionic interfaces shows that the presence of an interface plays the dominant role in determining the hydrogen bond dynamics, whereas the chemical nature of the interface plays a secondary role.

    View details for DOI 10.1073/pnas.0907875106

    View details for Web of Science ID 000269632400030

    View details for PubMedID 19706895

  • Water Dynamics in Salt Solutions Studied with Ultrafast Two-Dimensional Infrared (2D IR) Vibrational Echo Spectroscopy ACCOUNTS OF CHEMICAL RESEARCH Fayer, M. D., Moilanen, D. E., Wong, D., Rosenfeld, D. E., Fenn, E. E., Park, S. 2009; 42 (9): 1210-1219

    Abstract

    Water is ubiquitous in nature, but it exists as pure water infrequently. From the ocean to biology, water molecules interact with a wide variety of dissolved species. Many of these species are charged. In the ocean, water interacts with dissolved salts. In biological systems, water interacts with dissolved salts as well as charged amino acids, the zwitterionic head groups of membranes, and other biological groups that carry charges. Water plays a central role in a vast number of chemical processes because of its dynamic hydrogen-bond network. A water molecule can form up to four hydrogen bonds in an approximately tetrahedral arrangement. These hydrogen bonds are continually being broken, and new bonds are being formed on a picosecond time scale. The ability of the hydrogen-bond network of water to rapidly reconfigure enables water to accommodate and facilitate chemical processes. Therefore, the influence of charged species on water hydrogen-bond dynamics is important. Recent advances in ultrafast coherent infrared spectroscopy have greatly expanded our understanding of water dynamics. Two-dimensional infrared (2D IR) vibrational echo spectroscopy is providing new observables that yield direct information on the fast dynamics of molecules in their ground electronic state under thermal equilibrium conditions. The 2D IR vibrational echoes are akin to 2D nuclear magnetic resonance (NMR) but operate on time scales that are many orders of magnitude shorter. In a 2D IR vibrational echo experiment (see the Conspectus figure), three IR pulses are tuned to the vibrational frequency of interest, which in this case is the frequency of the hydroxyl stretching mode of water. The first two pulses "label" the initial molecular structures by their vibrational frequencies. The system evolves between pulses two and three, and the third pulse stimulates the emission of the vibrational echo pulse, which is the signal. The vibrational echo pulse is heterodyne, detected by combining it with another pulse, the local oscillator. Heterodyne detection provides phase and amplitude information, which are both necessary to perform the two Fourier transforms that take the data from the time domain to a two-dimensional frequency domain spectrum. The time dependence of a series of 2D IR vibrational echo spectra provides direct information on system dynamics. Here, we use two types of 2D IR vibrational echo experiments to examine the influence that charged species have on water hydrogen-bond dynamics. Solutions of NaBr and NaBF(4) are studied. The NaBr solutions are studied as a function of the concentration using vibrational echo measurements of spectral diffusion and polarization-selective IR pump-probe measurements of orientational relaxation. Both types of measurements show the slowing of hydrogen-bond network structural evolution with an increasing salt concentration. NaBF(4) is studied using vibrational echo chemical-exchange spectroscopy. In these experiments, it is possible to directly observe the chemical exchange of water molecules switching their hydrogen-bond partners between BF(4)(-) and other water molecules. The results demonstrate that water interacting with ions has slower hydrogen-bond dynamics than pure water, but the slowing is a factor of 3 or 4 rather than orders of magnitude.

    View details for DOI 10.1021/ar900043h

    View details for Web of Science ID 000269861400002

    View details for PubMedID 19378969

    View details for PubMedCentralID PMC2745496

  • Proton Transfer and Proton Concentrations in Protonated Nafion Fuel Cell Membranes JOURNAL OF PHYSICAL CHEMISTRY B Spry, D. B., Fayer, M. D. 2009; 113 (30): 10210-10221

    Abstract

    Proton transfer in protonated Nafion fuel cell membranes is studied using several pyrene derivative photoacids. Proton transfer in the center of the Nafion nanoscopic water channels is probed with the highly charged photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). At high hydration levels, both the time-integrated fluorescence spectrum and the fluorescence kinetics of HPTS permit the determination of hydronium concentration of the interior of the water pools in Nafion. The proton transfer kinetics of HPTS in protonated Nafion at maximum hydration are identical to the kinetics displayed by HPTS in a 0.5 M HCl solution. The hydronium concentration near the water interface in Nafion is estimated with rhodamine-6G to be 1.4 M. Excited state proton transfer (ESPT) is followed in the nonpolar side chain regions of Nafion with the photoacid 8-hydroxy-N,N,N',N',N'',N''-hexamethylpyrene-1,3,6-trisulfonamide (HPTA). Excited state proton transfer of HPTA is possible in protonated Nafion only at the highest hydration level due to a relatively high local pH.

    View details for DOI 10.1021/jp9036777

    View details for Web of Science ID 000268231000025

    View details for PubMedID 19572659

  • Water dynamics in large and small reverse micelles: From two ensembles to collective behavior JOURNAL OF CHEMICAL PHYSICS Moilanen, D. E., Fenn, E. E., Wong, D., Fayer, M. D. 2009; 131 (1)

    Abstract

    The dynamics of water in Aerosol-OT reverse micelles are investigated with ultrafast infrared spectroscopy of the hydroxyl stretch. In large reverse micelles, the dynamics of water are separable into two ensembles: slow interfacial water and bulklike core water. As the reverse micelle size decreases, the slowing effect of the interface and the collective nature of water reorientation begin to slow the dynamics of the core water molecules. In the smallest reverse micelles, these effects dominate and all water molecules have the same long time reorientational dynamics. To understand and characterize the transition in the water dynamics from two ensembles to collective reorientation, polarization and frequency selective infrared pump-probe experiments are conducted on the complete range of reverse micelle sizes from a diameter of 1.6-20 nm. The crossover between two ensemble and collective reorientation occurs near a reverse micelle diameter of 4 nm. Below this size, the small number of confined water molecules and structural changes in the reverse micelle interface leads to homogeneous long time reorientation.

    View details for DOI 10.1063/1.3159779

    View details for Web of Science ID 000267799100026

    View details for PubMedID 19586114

    View details for PubMedCentralID PMC2721765

  • Water Dynamics at the Interface in AOT Reverse Micelles JOURNAL OF PHYSICAL CHEMISTRY B Moilanen, D. E., Fenn, E. E., Wong, D., Fayer, M. D. 2009; 113 (25): 8560-8568

    Abstract

    The orientational dynamics of water molecules at the interface in large Aerosol-OT (AOT) reverse micelles are investigated using ultrafast infrared spectroscopy of the OD stretch of dilute HOD in H(2)O. In large reverse micelles ( approximately 9 nm diameter or larger), a significant amount of the nanoscopic water is sufficiently distant from the interface that it displays bulk-like characteristics. However, some water molecules interact with the interface and have vibrational absorption spectra and dynamics distinct from bulk water. The different characteristics of these interfacial waters allow their contribution to the data to be separated from the bulk. The infrared absorption spectrum of the OD stretch is analyzed to show that the interfacial water molecules have a spectrum that peaks near 2565 cm(-1) in contrast to 2509 cm(-1) in bulk water. A two-component model is developed that simultaneously describes the population relaxation and orientational dynamics of the OD stretch in the spectral region of the interfacial water. The model provides a consistent description of both observables and demonstrates that water interacting with the interface has slower vibrational relaxation and orientational dynamics. The orientational relaxation of interfacial water molecules occurs in 18 +/- 3 ps, in contrast to the bulk water value of 2.6 ps.

    View details for DOI 10.1021/jp902004r

    View details for Web of Science ID 000267205600023

    View details for PubMedID 19485407

  • Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar Structures and Reverse Micelles JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Moilanen, D. E., Fenn, E. E., Wong, D., Fayer, M. D. 2009; 131 (23): 8318-8328

    Abstract

    To determine the relative importance of the confining geometry and nanoscopic length scale versus water/interface interactions, the dynamic interactions between water and interfaces are studied with ultrafast infrared spectroscopy. Aerosol OT (AOT) is a surfactant that can form two-dimensional lamellar structures with known water layer thickness as well as well-defined monodispersed spherical reverse micelles of known water nanopool diameter. Lamellar structures and reverse micelles are compared based on two criteria: surface-to-surface dimensions to study the effect of confining length scales, and water-to-surfactant ratio to study water/interface interactions. We show that the water-to-surfactant ratio is the dominant factor governing the nature of water interacting with an interface, not the characteristic nanoscopic distance. The detailed structure of the interface and the specific interactions between water and the interface also play a critical role in the fraction of water molecules influenced by the surface. A two-component model in which water is separated into bulk-like water in the center of the lamellar structure or reverse micelle and interfacial water is used to quantitatively extract the interfacial dynamics. A greater number of perturbed water molecules are present in the lamellar structures as compared to the reverse micelles due to the larger surface area per AOT molecule and the greater penetration of water molecules past the sulfonate head groups in the lamellar structures.

    View details for DOI 10.1021/ja901950b

    View details for Web of Science ID 000267623100054

    View details for PubMedID 19449867

  • Water Dynamics and Interactions in Water-Polyether Binary Mixtures JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Fenn, E. E., Moilanen, D. E., Levinger, N. E., Fayer, M. D. 2009; 131 (15): 5530-5539

    Abstract

    Poly(ethylene) oxide (PEO) is a technologically important polymer with a wide range of applications including ion-exchange membranes, protein crystallization, and medical devices. PEO's versatility arises from its special interactions with water. Water molecules may form hydrogen-bond bridges between the ether oxygens of the backbone. While steady-state measurements and theoretical studies of PEO's interactions with water abound, experiments measuring dynamic observables are quite sparse. A major question is the nature of the interactions of water with the ether oxygens as opposed to the highly hydrophilic PEO terminal hydroxyls. Here, we examine a wide range of mixtures of water and tetraethylene glycol dimethyl ether (TEGDE), a methyl-terminated derivative of PEO with 4 repeat units (5 ether oxygens), using ultrafast infrared polarization selective pump-probe measurements on water's hydroxyl stretching mode to determine vibrational relaxation and orientational relaxation dynamics. The experiments focus on the dynamical interactions of water with the ether backbone because TEGDE does not have the PEO terminal hydroxyls. The experiments observe two distinct subensembles of water molecules: those that are hydrogen bonded to other waters and those that are associated with TEGDE molecules. The water orientational relaxation has a fast component of a few picoseconds (water-like) followed by much slower decay of approximately 20 ps (TEGDE associated). The two decay times vary only mildly with the water concentration. The two subensembles are evident even in very low water content samples, indicating pooling of water molecules. Structural change as water content is lowered through either conformational changes in the backbone or increasing hydrophobic interactions is discussed.

    View details for DOI 10.1021/ja809261d

    View details for Web of Science ID 000265268100036

    View details for PubMedID 19323522

    View details for PubMedCentralID PMC2889155

  • PHYS 430-Enzyme dynamical changes upon substrate binding and structural interconversions measured with ultrafast 2-D IR vibrational echo spectroscopy Fayer, M. D., Ishikawa, H., Finkelstein, I. J., Chung, J. K., Kwak, K., Kim, S. AMER CHEMICAL SOC. 2009
  • Ion-water hydrogen-bond switching observed with 2D IR vibrational echo chemical exchange spectroscopy PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Moilanen, D. E., Wong, D., Rosenfeld, D. E., Fenn, E. E., Fayer, M. D. 2009; 106 (2): 375-380

    Abstract

    The exchange of water hydroxyl hydrogen bonds between anions and water oxygens is observed directly with ultrafast 2D IR vibrational echo chemical exchange spectroscopy (CES). The OD hydroxyl stretch of dilute HOD in H(2)O in concentrated (5.5 M) aqueous solutions of sodium tetrafluoroborate (NaBF(4)) displays a spectrum with a broad water-like band (hydroxyl bound to water oxygen) and a resolved, blue shifted band (hydroxyl bound to BF(4)(-)). At short time (200 fs), the 2D IR vibrational echo spectrum has 4 peaks, 2 on the diagonal and 2 off-diagonal. The 2 diagonal peaks are the 0-1 transitions of the water-like band and the hydroxyl-anion band. Vibrational echo emissions at the 1-2 transition frequencies give rise to 2 off-diagonal peaks. On a picosecond time scale, additional off-diagonal peaks grow in. These new peaks arise from chemical exchange between water hydroxyls bound to anions and hydroxyls bound to water oxygens. The growth of the chemical exchange peaks yields the time dependence of anion-water hydroxyl hydrogen bond switching under thermal equilibrium conditions as T(aw) = 7 +/- 1 ps. Pump-probe measurements of the orientational relaxation rates and vibrational lifetimes are used in the CES data analysis. The pump-probe measurements are shown to have the correct functional form for a system undergoing exchange.

    View details for DOI 10.1073/pnas.0811489106

    View details for Web of Science ID 000262804000006

    View details for PubMedID 19106293

  • Dynamics of Liquids, Molecules, and Proteins Measured with Ultrafast 2D IR Vibrational Echo Chemical Exchange Spectroscopy ANNUAL REVIEW OF PHYSICAL CHEMISTRY Fayer, M. D. 2009; 60: 21-38

    Abstract

    A wide variety of molecular systems undergo fast structural changes under thermal equilibrium conditions. Such transformations are involved in a vast array of chemical problems. Experimentally measuring equilibrium dynamics is a challenging problem that is at the forefront of chemical research. This review describes ultrafast 2D IR vibrational echo chemical exchange experiments and applies them to several types of molecular systems. The formation and dissociation of organic solute-solvent complexes are directly observed. The dissociation times of 13 complexes, ranging from 4 ps to 140 ps, are shown to obey a relationship that depends on the complex's formation enthalpy. The rate of rotational gauche-trans isomerization around a carbon-carbon single bond is determined for a substituted ethane at room temperature in a low viscosity solvent. The results are used to obtain an approximate isomerization rate for ethane. Finally, the time dependence of a well-defined single structural transformation of a protein is measured.

    View details for DOI 10.1146/annurev-physchem-073108-112712

    View details for Web of Science ID 000268071200003

    View details for PubMedID 18851709

  • Ultrafast 2D-IR Vibration Echo Spectroscopy of Proteins Biological and Biomedical Infrared Spectroscopy Ishikawa, H., Kim, S., Finkelstein, I. J., Fayer, M. D. edited by Barth, A., Harris, P. I. IOS Press BV, Amsterdam. 2009
  • Water Dynamics at Neutral and Ionic Interfaces in Reverse Micelles Fenn, E. E., Wong, D. B., Fayer, M. D. 2009: 15243–48
  • Solute-Solvent Complex Switching Dynamics of Chloroform between Acetone and Dimethylsulfoxide-Two-Dimensional IR Chemical Exchange Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Kwak, K., Rosenfeld, D. E., Chung, J. K., Fayer, M. D. 2008; 112 (44): 13906-13915

    Abstract

    Hydrogen bonds formed between C-H and various hydrogen bond acceptors play important roles in the structure of proteins and organic crystals, and the mechanisms of C-H bond cleavage reactions. Chloroform, a C-H hydrogen bond donor, can form weak hydrogen-bonded complexes with acetone and with dimethylsulfoxide (DMSO). When chloroform is dissolved in a mixed solvent consisting of acetone and DMSO, both types of hydrogen-bonded complexes exist. The two complexes, chloroform-acetone and chloroform-DMSO, are in equilibrium, and they rapidly interconvert by chloroform exchanging hydrogen bond acceptors. This fast hydrogen bond acceptor substitution reaction is probed using ultrafast two-dimensional infrared (2D-IR) vibrational echo chemical exchange spectroscopy. Deuterated chloroform is used in the experiments, and the 2D-IR spectrum of the C-D stretching mode is measured. The chemical exchange of the chloroform hydrogen bonding partners is tracked by observing the time-dependent growth of off-diagonal peaks in the 2D-IR spectra. The measured substitution rate is 1/30 ps for an acetone molecule to replace a DMSO molecule in a chloroform-DMSO complex and 1/45 ps for a DMSO molecule to replace an acetone molecule in a chloroform-acetone complex. Free chloroform exists in the mixed solvent, and it acts as a reactive intermediate in the substitution reaction, analogous to a SN1 type reaction. From the measured rates and the equilibrium concentrations of acetone and DMSO, the dissociation rates for the chloroform-DMSO and chloroform-acetone complexes are found to be 1/24 ps and 1/5.5 ps, respectively. The difference between the measured rate for the complete substitution reaction and the rate for complex dissociation corresponds to the diffusion limited rate. The estimated diffusion limited rate agrees well with the result from a Smoluchowski treatment of diffusive reactions.

    View details for DOI 10.1021/jp806035w

    View details for Web of Science ID 000260533100027

    View details for PubMedID 18855462

    View details for PubMedCentralID PMC2646412

  • Water at the surfaces of aligned phospholipid multibilayer model membranes probed with ultrafast vibrational spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Zhao, W., Moilanen, D. E., Fenn, E. E., Fayer, M. D. 2008; 130 (42): 13927-13937

    Abstract

    The dynamics of water at the surface of artificial membranes composed of aligned multibilayers of the phospholipid dilauroyl phosphatidylcholine (DLPC) are probed with ultrafast polarization selective vibrational pump-probe spectroscopy. The experiments are performed at various hydration levels, x = 2 - 16 water molecules per lipid at 37 degrees C. The water molecules are approximately 1 nm above or below the membrane surface. The experiments are conducted on the OD stretching mode of dilute HOD in H 2O to eliminate vibrational excitation transfer. The FT-IR absorption spectra of the OD stretch in the DLPC bilayer system at low hydration levels shows a red-shift in frequency relative to bulk water, which is in contrast to the blue-shift often observed in systems such as water nanopools in reverse micelles. The spectra for x = 4 - 16 can be reproduced by a superposition of the spectra for x = 2 and bulk water. IR Pump-probe measurements reveal that the vibrational population decays (lifetimes) become longer as the hydration level is decreased. The population decays are fit well by biexponential functions. The population decays, measured as a function of the OD stretch frequency, suggest the existence of two major types of water molecules in the interfacial region of the lipid bilayers. One component may be a clathrate-like water cluster near the hydrophobic choline group and the other may be related to the hydration water molecules mainly associated with the phosphate group. As the hydration level increases, the vibrational lifetimes of these two components decrease, suggesting a continuous evolution of the hydration structures in the two components associated with the swelling of the bilayers. The agreement of the magnitudes of the two components obtained from IR spectra with those from vibrational lifetime measurements further supports the two-component model. The vibrational population decay fitting also gives an estimation of the number of phosphate-associated water molecules and choline-associated water molecules, which range from 1 to 4 and 1 to 12, respectively, as x increases from 2 to 16. Time-dependent anisotropy measurements yield the rate of orientational relaxation as a function of x. The anisotropy decay is biexponential. The fast component is almost independent of x, and is interpreted as small orientational fluctuations that occur without hydrogen-bond rearrangement. The slower component becomes very long as the hydration level decreases. This component is a measure of the rate of complete orientational randomization, which requires H-bond rearrangement and is discussed in terms of a jump reorientation model.

    View details for DOI 10.1021/ja803252y

    View details for Web of Science ID 000260047700037

    View details for PubMedID 18823116

    View details for PubMedCentralID PMC2648527

  • Charge Transfer in Photoacids Observed by Stark Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY A Silverman, L. N., Spry, D. B., Boxer, S. G., Fayer, M. D. 2008; 112 (41): 10244-10249

    Abstract

    The charge redistribution upon photoexcitation is investigated for a series of pyrene photoacids to better understand the driving force behind excited-state proton-transfer processes. The changes in electric dipole for the lowest two electronic transitions ( (1)L b and (1)L a) are measured by Stark spectroscopy, and the magnitudes of charge transfer of the protonated and deprotonated states are compared. For neutral photoacids studied here, the results show that the amount of charge transfer depends more upon the electronic state that is excited than the protonation state. Transitions from the ground state to the (1)L b state result in a much smaller change in electric dipole than transitions to the (1)L a state. Conversely, for the cationic (ammonium) photoacid studied, photoexcitation of a particular electronic state results in much smaller charge transfer for the protonated state than for the deprotonated state.

    View details for DOI 10.1021/jp805189u

    View details for Web of Science ID 000259943100022

    View details for PubMedID 18798602

  • Solute-solvent complex kinetics and thermodynamics probed by 2D-IR vibrational echo chemical exchange Spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Zheng, J., Fayer, M. D. 2008; 112 (33): 10221-10227

    Abstract

    The formation and dissociation kinetics of a series of triethylsilanol/solvent weakly hydrogen bonding complexes with enthalpies of formation ranging from -1.4 to -3.3 kcal/mol are measured with ultrafast two-dimensional infrared (2D IR) chemical exchange spectroscopy in liquid solutions at room temperature. The correlation between the complex enthalpies of formation and dissociation rate constants can be expressed with an equation similar to the Arrhenius equation. The experimental results are in accord with previous observations on eight phenol/solvent complexes with enthalpies of formation from -0.6 to -2.5 kcal/mol. It was found that the inverse of the solute-solvent complex dissociation rate constant is linearly related to exp(-DeltaH0/RT) where DeltaH0 is the complex enthalpy of formation. It is shown here, that the triethylsilanol-solvent complexes obey the same relationship with the identical proportionality constant, that is, all 13 points, five silanol complexes and eight phenol complexes, fall on the same line. In addition, features of 2D IR chemical exchange spectra at long reaction times (spectral diffusion complete) are explicated using the triethylsilanol systems. It is shown that the off-diagonal chemical exchange peaks have shapes that are a combination (outer product) of the absorption line shapes of the species that give rise to the diagonal peaks.

    View details for DOI 10.1021/jp804087v

    View details for Web of Science ID 000258460400022

    View details for PubMedID 18665635

  • PHYS 286-Dynamics of native and unfolded cytochrome c using 2-D-IR vibrational echo spectroscopy 236th National Meeting of the American-Chemical-Society Fayer, M. D., Kim, S., Chung, J. K., Bowman, S. E., Bren, K. L., Bagchi, B. AMER CHEMICAL SOC. 2008
  • Native and unfolded cytochrome c-comparison of dynamics using 2D-IR vibrational echo spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Kim, S., Chung, J. K., Kwak, K., Bowman, S. E., Bren, K. L., Bagchi, B., Fayer, M. D. 2008; 112 (32): 10054-10063

    Abstract

    Unfolded vs native CO-coordinated horse heart cytochrome c (h-cyt c) and a heme axial methionine mutant cyt c552 from Hydrogenobacter thermophilus ( Ht-M61A) are studied by IR absorption spectroscopy and ultrafast 2D-IR vibrational echo spectroscopy of the CO stretching mode. The unfolding is induced by guanidinium hydrochloride (GuHCl). The CO IR absorption spectra for both h-cyt c and Ht-M61A shift to the red as the GuHCl concentration is increased through the concentration region over which unfolding occurs. The spectra for the unfolded state are substantially broader than the spectra for the native proteins. A plot of the CO peak position vs GuHCl concentration produces a sigmoidal curve that overlays the concentration-dependent circular dichroism (CD) data of the CO-coordinated forms of both Ht-M61A and h-cyt c within experimental error. The coincidence of the CO peak shift curve with the CD curves demonstrates that the CO vibrational frequency is sensitive to the structural changes induced by the denaturant. 2D-IR vibrational echo experiments are performed on native Ht-M61A and on the protein in low- and high-concentration GuHCl solutions. The 2D-IR vibrational echo is sensitive to the global protein structural dynamics on time scales from subpicosecond to greater than 100 ps through the change in the shape of the 2D spectrum with time (spectral diffusion). At the high GuHCl concentration (5.1 M), at which Ht-M61A is essentially fully denatured as judged by CD, a very large reduction in dynamics is observed compared to the native protein within the approximately 100 ps time window of the experiment. The results suggest the denatured protein may be in a glassy-like state involving hydrophobic collapse around the heme.

    View details for DOI 10.1021/jp802246h

    View details for Web of Science ID 000258290000060

    View details for PubMedID 18646797

    View details for PubMedCentralID PMC2671645

  • Direct observation of fast protein conformational switching PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Ishikawa, H., Kwak, K., Chung, J. K., Kim, S., Fayer, M. D. 2008; 105 (25): 8619-8624

    Abstract

    Folded proteins can exist in multiple conformational substates. Each substate reflects a local minimum on the free-energy landscape with a distinct structure. By using ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy, conformational switching between two well defined substates of a myoglobin mutant is observed on the approximately 50-ps time scale. The conformational dynamics are directly measured through the growth of cross peaks in the 2D-IR spectra of CO bound to the heme active site. The conformational switching involves motion of the distal histidine/E helix that changes the location of the imidazole side group of the histidine. The exchange between substates changes the frequency of the CO, which is detected by the time dependence of the 2D-IR vibrational echo spectrum. These results demonstrate that interconversion between protein conformational substates can occur on very fast time scales. The implications for larger structural changes that occur on much longer time scales are discussed.

    View details for DOI 10.1073/pnas.0803764105

    View details for Web of Science ID 000257185700026

    View details for PubMedID 18562286

    View details for PubMedCentralID PMC2438383

  • Taking apart the two-dimensional infrared vibrational echo spectra: More information and elimination of distortions JOURNAL OF CHEMICAL PHYSICS Kwak, K., Rosenfeld, D. E., Fayer, M. D. 2008; 128 (20)

    Abstract

    Ultrafast two-dimensional infrared (2D-IR) vibrational echo spectroscopy can probe the fast structural evolution of molecular systems under thermal equilibrium conditions. Structural dynamics are tracked by observing the time evolution of the 2D-IR spectrum, which is caused by frequency fluctuations of vibrational mode(s) excited during the experiment. However, there are a variety of effects that can produce line shape distortions and prevent the correct determination of the frequency-frequency correlation function (FFCF), which describes the frequency fluctuations and connects the experimental observables to a molecular level depiction of dynamics. In addition, it can be useful to analyze different parts of the 2D spectrum to determine if dynamics are different for subensembles of molecules that have different initial absorption frequencies in the inhomogeneously broadened absorption line. Here, an important extension to a theoretical method for extraction of the FFCF from 2D-IR spectra is described. The experimental observable is the center line slope (CLSomega(m)) of the 2D-IR spectrum. The CLSomega(m) is obtained by taking slices through the 2D spectrum parallel to the detection frequency axis (omega(m)). Each slice is a spectrum. The slope of the line connecting the frequencies of the maxima of the sliced spectra is the CLSomega(m). The change in slope of the CLSomega(m) as a function of time is directly related to the FFCF and can be used to obtain the complete FFCF. CLSomega(m) is immune to line shape distortions caused by destructive interference between bands arising from vibrational echo emission, from the 0-1 vibrational transition (positive), and from the 1-2 vibrational transition (negative) in the 2D-IR spectrum. The immunity to the destructive interference enables the CLSomega(m) method to compare different parts of the bands as well as comparing the 0-1 and 1-2 bands. Also, line shape distortions caused by solvent background absorption and finite pulse durations do not affect the determination of the FFCF with the CLSomega(m) method. The CLSomega(m) can also provide information on the cross correlation between frequency fluctuations of the 0-1 and 1-2 vibrational transitions.

    View details for DOI 10.1063/1.2927906

    View details for Web of Science ID 000256304200031

    View details for PubMedID 18513030

  • Water dynamics - The effects of ions and nanoconfinement JOURNAL OF PHYSICAL CHEMISTRY B Park, S., Moilanen, D. E., Fayer, M. D. 2008; 112 (17): 5279-5290

    Abstract

    Hydrogen bond dynamics of water in highly concentrated NaBr salt solutions and reverse micelles are studied using ultrafast 2D-IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments performed on the OD hydroxyl stretch of dilute HOD in H(2)O. The vibrational echo experiments measure spectral diffusion, and the pump-probe experiments measure orientational relaxation. Both experimental observables are directly related to the structural dynamics of water's hydrogen bond network. The measurements performed on NaBr solutions as a function of concentration show that the hydrogen bond dynamics slow as the NaBr concentration increases. The most pronounced change is in the longest time scale dynamics which are related to the global rearrangement of the hydrogen bond structure. Complete hydrogen bond network randomization slows by a factor of approximately 3 in approximately 6 M NaBr solution compared to that in bulk water. The hydrogen bond dynamics of water in nanoscopically confined environments are studied by encapsulating water molecules in ionic head group (AOT) and nonionic head group (Igepal CO 520) reverse micelles. Water dynamics in the nanopools of AOT reverse micelles are studied as a function of size by observing orientational relaxation. Orientational relaxation dynamics deviate significantly from bulk water when the size of the reverse micelles is smaller than several nm and become nonexponential and slower as the size of the reverse micelles decreases. In the smallest reverse micelles, orientational relaxation (hydrogen bond structural randomization) is almost 20 times slower than that in bulk water. To determine if the changes in dynamics from bulk water are caused by the influence of the ionic head groups of AOT or the nanoconfinement, the water dynamics in 4 nm nanopools in AOT reverse micelles (ionic) and Igepal reverse micelles (nonionic) are compared. It is found that the water orientational relaxation in the 4 nm diameter nanopools of the two types of reverse micelles is almost identical, which indicates that confinement by an interface to form a nanoscopic water pool is a primary factor governing the dynamics of nanoscopic water rather than the presence of charged groups at the interface.

    View details for DOI 10.1021/jp7121856

    View details for Web of Science ID 000255292300005

    View details for PubMedID 18370431

  • Water dynamics and proton transfer in Nafion fuel cell membranes LANGMUIR Moilanen, D. E., Spry, D. B., Fayer, M. D. 2008; 24 (8): 3690-3698

    Abstract

    The dynamics of water and its effect on proton transport kinetics in Nafion membranes are compared at several hydration levels. Nafion is the most widely used polyelectrolyte membrane in fuel cells. Ultrafast infrared spectroscopy of the O-D stretch of dilute HOD in H2O provides a probe of the local environment and hydrogen bond network dynamics of water confined in the hydrophilic regions of Nafion. The kinetics of proton transfer in Nafion are tracked by following the excited-state proton transfer and recombination kinetics of a molecular probe, pyranine (HPTS). The hydrophilic domains of Nafion grow with increased hydration, and the interfacial regions reorganize, leading to a changing local environment for water near the interface. Swelling is not uniform throughout the membrane, and heterogeneity is observed in the fluorescence anisotropy decays of the methoxy derivative of pyranine. Measurements of the time-dependent anisotropy of water in Nafion provide a direct probe of the hydrogen bond network dynamics. These dynamics, as well as the rate of proton transport over nanoscopic distances, are observed to slow significantly as the hydration level of the membrane decreases. The results provide insights into the influence of changes in the dynamics of water on the proton-transfer processes.

    View details for DOI 10.1021/la703358a

    View details for Web of Science ID 000254647400003

    View details for PubMedID 18220436

  • Water inertial reorientation: Hydrogen bond strength and the angular potential PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Moilanen, D. E., Fenn, E. E., Lin, Y., Skinner, J. L., Bagchi, B., Fayer, M. D. 2008; 105 (14): 5295-5300

    Abstract

    The short-time orientational relaxation of water is studied by ultrafast infrared pump-probe spectroscopy of the hydroxyl stretching mode (OD of dilute HOD in H(2)O). The anisotropy decay displays a sharp drop at very short times caused by inertial orientational motion, followed by a much slower decay that fully randomizes the orientation. Investigation of temperatures from 1 degrees C to 65 degrees C shows that the amplitude of the inertial component (extent of inertial angular displacement) depends strongly on the stretching frequency of the OD oscillator at higher temperatures, although the slow component is frequency-independent. The inertial component becomes frequency-independent at low temperatures. At high temperatures there is a correlation between the amplitude of the inertial decay and the strength of the O-D O hydrogen bond, but at low temperatures the correlation disappears, showing that a single hydrogen bond (OD O) is no longer a significant determinant of the inertial angular motion. It is suggested that the loss of correlation at lower temperatures is caused by the increased importance of collective effects of the extended hydrogen bonding network. By using a new harmonic cone model, the experimentally measured amplitudes of the inertial decays yield estimates of the characteristic frequencies of the intermolecular angular potential for various strengths of hydrogen bonds. The frequencies are in the range of approximately 400 cm(-1). A comparison with recent molecular dynamics simulations employing the simple point charge-extended water model at room temperature shows that the simulations qualitatively reflect the correlation between the inertial decay and the OD stretching frequency.

    View details for DOI 10.1073/pnas.0801554105

    View details for Web of Science ID 000254893600004

    View details for PubMedID 18381817

    View details for PubMedCentralID PMC2291089

  • Charge redistribution and photoacidity: Neutral versus cationic photoacids JOURNAL OF CHEMICAL PHYSICS Spry, D. B., Fayer, M. D. 2008; 128 (8)

    Abstract

    A series of pyrene photoacids is used to investigate excited-state proton transfer with time-dependent pump-probe spectroscopy. The deprotonation dynamics of a cationic photoacid, 8-aminopyrene-1,3,6-trisulfonic acid trisodium salt (APTS), shows single exponential dynamics( approximately 30 ps) in water. This is in contrast to what is observed for the neutral photoacids 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and 8-hydroxy-N,N,N',N',N",N"-hexamethylpyrene-1,3,6-trisulfonamide, which display biexponential dynamics. For the cationic photoacid, the vast majority of the intramolecular charge redistribution does not occur in the protonated state. Instead, the charge redistribution, which is responsible for the photoacidity and the observed spectroscopic changes, occurs primarily following the excited-state proton transfer. The lack of charge redistribution prior to proton transfer causes APTS to display single exponential kinetics. In contrast, the dynamics for the neutral photoacids are multiexponential because major charge redistribution precedes proton transfer followed by additional charge redistribution that accompanies proton transfer. Previous studies of HPTS in water are discussed in terms of the results presented here.

    View details for DOI 10.1063/1.2825297

    View details for Web of Science ID 000254047200036

    View details for PubMedID 18315062

  • Disulfide bond influence on protein structural dynamics probed with 2D-IR vibrational echo spectroscopy PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Ishikawa, H., Kim, S., Kwak, K., Wakasugi, K., Fayer, M. D. 2007; 104 (49): 19309-19314

    Abstract

    Intramolecular disulfide bonds are understood to play a role in regulating protein stability and activity. Because disulfide bonds covalently link different components of a protein, they influence protein structure. However, the effects of disulfide bonds on fast (subpicosecond to approximately 100 ps) protein equilibrium structural fluctuations have not been characterized experimentally. Here, ultrafast 2D-IR vibrational echo spectroscopy is used to examine the constraints an intramolecular disulfide bond places on the structural fluctuations of the protein neuroglobin (Ngb). Ngb is a globin family protein found in vertebrate brains that binds oxygen reversibly. Like myoglobin (Mb), Ngb has the classical globin fold and key residues around the heme are conserved. Furthermore, the heme-ligated CO vibrational spectra of Mb (Mb-CO) and Ngb (Ngb-CO) are virtually identical. However, in contrast to Mb, human Ngb has an intramolecular disulfide bond that affects its oxygen affinity and protein stability. By using 2D-IR vibrational echo spectroscopy, we investigated the equilibrium protein dynamics of Ngb-CO by observing the CO spectral diffusion (time dependence of the 2D-IR line shapes) with and without the disulfide bond. Despite the similarity of the linear FTIR spectra of Ngb-CO with and without the disulfide bond, 2D-IR measurements reveal that the equilibrium sampling of different protein configurations is accelerated by disruption of the disulfide bond. The observations indicate that the intramolecular disulfide bond in Ngb acts as an inhibitor of fast protein dynamics even though eliminating it does not produce significant conformational change in the protein's structure.

    View details for DOI 10.1073/pnas.0709760104

    View details for Web of Science ID 000251525800028

    View details for PubMedID 18042705

    View details for PubMedCentralID PMC2148286

  • Observation of slow charge redistribution preceding excited-state proton transfer JOURNAL OF CHEMICAL PHYSICS Spry, D. B., Fayer, M. D. 2007; 127 (20)

    Abstract

    The photoacid 8-hydroxy-N,N,N',N',N',N'-hexamethylpyrene-1,3,6-trisulfonamide (HPTA) and related compounds are used to investigate the steps involved in excited-state deprotonation in polar solvents using pump-probe spectroscopy and time correlated single photon counting fluorescence spectroscopy. The dynamics show a clear two-step process leading to excited-state proton transfer. The first step after electronic excitation is charge redistribution occurring on a tens of picoseconds time scale followed by proton transfer on a nanosecond time scale. The three states observed in the experiments (initial excited state, charge redistributed state, and proton transfer state) are recognized by distinct features in the time dependence of the pump-probe spectrum and fluorescence spectra. In the charge redistributed state, charge density has transferred from the hydroxyl oxygen to the pyrene ring, but the OH sigma bond is still intact. The experiments indicate that the charge redistribution step is controlled by a specific hydrogen bond donation from HPTA to the accepting base molecule. The second step is the full deprotonation of the photoacid. The full deprotonation is clearly marked by the growth of stimulated emission spectral band in the pump-probe spectrum that is identical to the fluorescence spectrum of the anion.

    View details for DOI 10.1063/1.2803188

    View details for Web of Science ID 000251325100025

    View details for PubMedID 18052436

  • Confinement or the nature of the interface? Dynamics of nanoscopic water JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Moilanen, D. E., Levinger, N. E., Spry, D. B., Fayer, M. D. 2007; 129 (46): 14311-14318

    Abstract

    The dynamics of water confined in two different types of reverse micelles are studied using ultrafast infrared pump-probe spectroscopy of the hydroxyl OD stretch of HOD in H2O. Reverse micelles of the surfactant Aerosol-OT (ionic head group) in isooctane and the surfactant Igepal CO 520 (nonionic head group) in 50/50 wt % cyclohexane/hexane are prepared to have the same diameter water nanopools. Measurements of the IR spectra and vibrational lifetimes show that the identity of the surfactant head groups affects the local environment experienced by the water molecules inside the reverse micelles. The orientational dynamics (time-dependent anisotropy), which is a measure of the hydrogen bond network rearrangement, are very similar for the confined water in the two types of reverse micelles. The results demonstrate that confinement by an interface to form a nanoscopic water pool is a primary factor governing the dynamics of nanoscopic water rather than the presence of charged groups at the interface.

    View details for DOI 10.1021/ja073977d

    View details for Web of Science ID 000251182000056

    View details for PubMedID 17958424

  • Are water simulation models consistent with steady-state and ultrafast vibrational spectroscopy experiments? CHEMICAL PHYSICS Schmidt, J. R., Roberts, S. T., Loparo, J. J., Tokmakoff, A., Fayer, M. D., Skinner, J. L. 2007; 341 (1-3): 143-157
  • Hydrogen bond dynamics in aqueous NaBr solutions PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Park, S., Fayer, M. D. 2007; 104 (43): 16731-16738

    Abstract

    Hydrogen bond dynamics of water in NaBr solutions are studied by using ultrafast 2D IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments. The hydrogen bond structural dynamics are observed by measuring spectral diffusion of the OD stretching mode of dilute HOD in H(2)O in a series of high concentration aqueous NaBr solutions with 2D IR vibrational echo spectroscopy. The time evolution of the 2D IR spectra yields frequency-frequency correlation functions, which permit quantitative comparisons of the influence of NaBr concentration on the hydrogen bond dynamics. The results show that the global rearrangement of the hydrogen bond structure, which is represented by the slowest component of the spectral diffusion, slows, and its time constant increases from 1.7 to 4.8 ps as the NaBr concentration increases from pure water to approximately 6 M NaBr. Orientational relaxation is analyzed with a wobbling-in-a-cone model describing restricted orientational diffusion that is followed by complete orientational randomization described as jump reorientation. The slowest component of the orientational relaxation increases from 2.6 ps (pure water) to 6.7 ps (approximately equal to 6 M NaBr). Vibrational population relaxation of the OD stretch also slows significantly as the NaBr concentration increases.

    View details for Web of Science ID 000250487600005

    View details for PubMedID 17940023

    View details for PubMedCentralID PMC2040434

  • Neuroglobin dynamics observed with ultrafast 2D-IR vibrational echo spectroscopy PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Ishikawa, H., Finkelstein, I. J., Kim, S., Kwak, K., Chung, J. K., Wakasugi, K., Massari, A. M., Fayer, M. D. 2007; 104 (41): 16116-16121

    Abstract

    Neuroglobin (Ngb), a protein in the globin family, is found in vertebrate brains. It binds oxygen reversibly. Compared with myoglobin (Mb), the amino acid sequence has limited similarity, but key residues around the heme and the classical globin fold are conserved in Ngb. The CO adduct of Ngb displays two CO absorption bands in the IR spectrum, referred to as N(3) (distal histidine in the pocket) and N(0) (distal histidine swung out of the pocket), which have absorption spectra that are almost identical with the Mb mutants L29F and H64V, respectively. The Mb mutants mimic the heme pocket structures of the corresponding Ngb conformers. The equilibrium protein dynamics for the CO adduct of Ngb are investigated by using ultrafast 2D-IR vibrational echo spectroscopy by observing the CO vibration's spectral diffusion (2D-IR spectra time dependence) and comparing the results with those for the Mb mutants. Although the heme pocket structure and the CO FTIR peak positions of Ngb are similar to those of the mutant Mb proteins, the 2D-IR results demonstrate that the fast structural fluctuations of Ngb are significantly slower than those of the mutant Mbs. The results may also provide some insights into the nature of the energy landscape in the vicinity of the folded protein free energy minimum.

    View details for DOI 10.1073/pnas.0707718104

    View details for Web of Science ID 000250128800028

    View details for PubMedID 17916624

    View details for PubMedCentralID PMC2042171

  • Ultrafast 2D-IR vibrational echo spectroscopy: a probe of molecular dynamics LASER PHYSICS LETTERS Park, S., Kwak, K., Fayer, M. D. 2007; 4 (10): 704-718
  • Frequency-frequency correlation functions and apodization in two-dimensional infrared vibrational echo spectroscopy: A new approach JOURNAL OF CHEMICAL PHYSICS Kwak, K., Park, S., Finkelstein, I. J., Fayer, M. D. 2007; 127 (12)

    Abstract

    Ultrafast two-dimensional infrared (2D-IR) vibrational echo spectroscopy can probe structural dynamics under thermal equilibrium conditions on time scales ranging from femtoseconds to approximately 100 ps and longer. One of the important uses of 2D-IR spectroscopy is to monitor the dynamical evolution of a molecular system by reporting the time dependent frequency fluctuations of an ensemble of vibrational probes. The vibrational frequency-frequency correlation function (FFCF) is the connection between the experimental observables and the microscopic molecular dynamics and is thus the central object of interest in studying dynamics with 2D-IR vibrational echo spectroscopy. A new observable is presented that greatly simplifies the extraction of the FFCF from experimental data. The observable is the inverse of the center line slope (CLS) of the 2D spectrum. The CLS is the inverse of the slope of the line that connects the maxima of the peaks of a series of cuts through the 2D spectrum that are parallel to the frequency axis associated with the first electric field-matter interaction. The CLS varies from a maximum of 1 to 0 as spectral diffusion proceeds. It is shown analytically to second order in time that the CLS is the T(w) (time between pulses 2 and 3) dependent part of the FFCF. The procedure to extract the FFCF from the CLS is described, and it is shown that the T(w) independent homogeneous contribution to the FFCF can also be recovered to yield the full FFCF. The method is demonstrated by extracting FFCFs from families of calculated 2D-IR spectra and the linear absorption spectra produced from known FFCFs. Sources and magnitudes of errors in the procedure are quantified, and it is shown that in most circumstances, they are negligible. It is also demonstrated that the CLS is essentially unaffected by Fourier filtering methods (apodization), which can significantly increase the efficiency of data acquisition and spectral resolution, when the apodization is applied along the axis used for obtaining the CLS and is symmetrical about tau=0. The CLS is also unchanged by finite pulse durations that broaden 2D spectra.

    View details for DOI 10.1063/1.2772269

    View details for Web of Science ID 000249787300033

    View details for PubMedID 17902917

  • Dynamics around solutes and solute-solvent complexes in mixed solvents PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kwak, K., Park, S., Fayer, M. D. 2007; 104 (36): 14221-14226

    Abstract

    Ultrafast 2D-IR vibrational echo experiments, IR pump-probe experiments, and FT-IR spectroscopy of the hydroxyl stretch of phenol-OD in three solvents, CCl4, mesitylene (1, 3, 5 trimethylbenzene), and the mixed solvent of mesitylene and CCl4 (0.83 mole fraction CCl4), are used to study solute-solvent dynamics via observation of spectral diffusion. Phenol forms a complex with Mesitylene. In the mesitylene solution, there is only complexed phenol; in the CCl4 solution, there is only uncomplexed phenol; and in the mixed solvent, both phenol species are present. Dynamics of the free phenol in CCl4 or the mixed solvent are very similar, and dynamics of the complex in mesitylene and in the mixed solvent are very similar. However, there are differences in the slowest time scale dynamics between the pure solvents and the mixed solvents. The mixed solvent produces slower dynamics that are attributed to first solvent shell solvent composition variations. The composition variations require a longer time to randomize than is required in the pure solvents, where only density variations occur. The experimental results and recent MD simulations indicate that the solvent structure around the solute may be different from the mixed solvent's mole fraction.

    View details for DOI 10.1073/pnas.0701710104

    View details for Web of Science ID 000249333600010

    View details for PubMedID 17581876

    View details for PubMedCentralID PMC1964852

  • Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Spry, D. B., Goun, A., Glusac, K., Moilanen, D. E., Fayer, M. D. 2007; 129 (26): 8122-8130

    Abstract

    The properties of confined water and diffusive proton-transfer kinetics in the nanoscopic water channels of Nafion fuel cell membranes at various hydration levels are compared to water in a series of well-characterized AOT reverse micelles with known water nanopool sizes using the photoacid pyranine as a molecular probe. The side chains of Nafion are terminated by sulfonate groups with sodium counterions that are arrayed along the water channels. AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. The extent of excited-state deprotonation is observed by steady-state fluorescence measurements. Proton-transfer kinetics and orientational relaxation are measured by time-dependent fluorescence using time-correlated single photon counting. The time dependence of deprotonation is related to diffusive proton transport away from the photoacid. The fluorescence reflecting the long time scale proton transport has an approximately t-0.8 power law decay in contrast to bulk water, which has a t-3/2 power law. For a given hydration level of Nafion, the excited-state proton transfer and the orientational relaxation are similar to those observed for a related size AOT water nanopool. The effective size of the Nafion water channels at various hydration levels are estimated by the known size of the AOT reverse micelles that display the corresponding proton-transfer kinetics and orientational relaxation.

    View details for DOI 10.1021/ja071939o

    View details for Web of Science ID 000247563700025

    View details for PubMedID 17567012

  • Water dynamics in nafion fuel cell membranes: The effects of confinement and structural changes on the hydrogen bond network JOURNAL OF PHYSICAL CHEMISTRY C Moilanen, D. E., Piletic, I. R., Fayer, M. D. 2007; 111 (25): 8884-8891

    Abstract

    The complex environments experienced by water molecules in the hydrophilic channels of Nafion membranes are studied by ultrafast infrared pump-probe spectroscopy. A wavelength dependent study of the vibrational lifetime of the O-D stretch of dilute HOD in H(2)O confined in Nafion membranes provides evidence of two distinct ensembles of water molecules. While only two ensembles are present at each level of membrane hydration studied, the characteristics of the two ensembles change as the water content of the membrane changes. Time dependent anisotropy measurements show that the orientational motions of water molecules in Nafion membranes are significantly slower than in bulk water and that lower hydration levels result in slower orientational relaxation. Initial wavelength dependent results for the anisotropy show no clear variation in the time scale for orientational motion across a broad range of frequencies. The anisotropy decay is analyzed using a model based on restricted orientational diffusion within a hydrogen bond configuration followed by total reorientation through jump diffusion.

    View details for DOI 10.1021/jp067460k

    View details for Web of Science ID 000247601900022

    View details for PubMedCentralID PMC2523265

  • Viscosity-dependent protein dynamics BIOPHYSICAL JOURNAL Finkelstein, I. J., Massari, A. M., Fayer, M. D. 2007; 92 (10): 3652-3662

    Abstract

    Spectrally resolved stimulated vibrational echo spectroscopy is used to investigate the dependence of fast protein dynamics on bulk solution viscosity at room temperature in four heme proteins: hemoglobin, myoglobin, a myoglobin mutant with the distal histidine replaced by a valine (H64V), and a cytochrome c552 mutant with the distal methionine replaced by an alanine (M61A). Fructose is added to increase the viscosity of the aqueous protein solutions over many orders of magnitude. The fast dynamics of the four globular proteins were found to be sensitive to solution viscosity and asymptotically approached the dynamical behavior that was previously observed in room temperature sugar glasses. The viscosity-dependent protein dynamics are analyzed in the context of a viscoelastic relaxation model that treats the protein as a deformable breathing sphere. The viscoelastic model is in qualitative agreement with the experimental data but does not capture sufficient system detail to offer a quantitative description of the underlying fluctuation amplitudes and relaxation rates. A calibration method based on the near-infrared spectrum of water overtones was constructed to accurately determine the viscosity of small volumes of protein solutions.

    View details for DOI 10.1529/biophysj.106.093708

    View details for Web of Science ID 000245852600029

    View details for PubMedID 17446536

  • Hydrogen bond lifetimes and energetics for solute/solvent complexes studied with 2D-IR vibrational echo spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Zheng, J., Fayer, M. D. 2007; 129 (14): 4328-4335

    Abstract

    Weak pi hydrogen-bonded solute/solvent complexes are studied with ultrafast two-dimensional infrared (2D-IR) vibrational echo chemical exchange spectroscopy, temperature-dependent IR absorption spectroscopy, and density functional theory calculations. Eight solute/solvent complexes composed of a number of phenol derivatives and various benzene derivatives are investigated. The complexes are formed between the phenol derivative (solute) in a mixed solvent of the benzene derivative and CCl4. The time dependence of the 2D-IR vibrational echo spectra of the phenol hydroxyl stretch is used to directly determine the dissociation and formation rates of the hydrogen-bonded complexes. The dissociation rates of the weak hydrogen bonds are found to be strongly correlated with their formation enthalpies. The correlation can be described with an equation similar to the Arrhenius equation. The results are discussed in terms of transition state theory.

    View details for DOI 10.1021/ja067760f

    View details for Web of Science ID 000245723800048

    View details for PubMedID 17373792

    View details for PubMedCentralID PMC2522382

  • Ultrafast 2-D infrared vibrational echo chemical exchange spectroscopy studies of chemical processes Fayer, M. D., Zheng, J., Kwak, K. AMER CHEMICAL SOC. 2007
  • Substrate binding and protein conformational dynamics measured by 2D-IR vibrational echo spectroscopy PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Finkelstein, I. J., Ishikawa, H., Kim, S., Massari, A. M., Fayer, M. D. 2007; 104 (8): 2637-2642

    Abstract

    Enzyme structural dynamics play a pivotal role in substrate binding and biological function, but the influence of substrate binding on enzyme dynamics has not been examined on fast time scales. In this work, picosecond dynamics of horseradish peroxidase (HRP) isoenzyme C in the free form and when ligated to a variety of small organic molecule substrates is studied by using 2D-IR vibrational echo spectroscopy. Carbon monoxide bound at the heme active site of HRP serves as a spectroscopic marker that is sensitive to the structural dynamics of the protein. In the free form, HRP assumes two distinct spectroscopic conformations that undergo fluctuations on a tens-of-picoseconds time scale. After substrate binding, HRP is locked into a single conformation that exhibits reduced amplitudes and slower time-scale structural dynamics. The decrease in carbon monoxide frequency fluctuations is attributed to reduced dynamic freedom of the distal histidine and the distal arginine, which are key residues in modulating substrate binding affinity. It is suggested that dynamic quenching caused by substrate binding can cause the protein to be locked into a conformation suitable for downstream steps in the enzymatic cycle of HRP.

    View details for DOI 10.1073/pnas.0610027104

    View details for Web of Science ID 000244511200016

    View details for PubMedID 17296942

    View details for PubMedCentralID PMC1815234

  • Deprotonation dynamics and stokes shift of pyranine (HPTS) JOURNAL OF PHYSICAL CHEMISTRY A Spry, D. B., Goun, A., Fayer, M. D. 2007; 111 (2): 230-237

    Abstract

    The short and intermediate time scale dynamics of the photoacid pyranine (1-hydroxy-3,6,8-pyrenetrisulfonic acid, commonly referred to as HPTS) are studied with visible pump-probe spectroscopy in various solvents to elucidate the nature of its proton-transfer kinetics in water. The observed time dependences of HPTS are compared with those of the methoxy derivative, MPTS. A global fitting procedure is employed to model both the spectral shift (Stokes shift) caused by solvent reorganization and deprotonation of pyranine in water. Three distinct time-dependent features can be clearly identified. They are the Stokes shift (1 ps in H(2)O and 1.5 ps in D(2)O), followed by the deprotonation processes, which gives rise to a biexponential decay of the protonated species with time constants (in H(2)O) of 3 and 88 ps. By the use of a model previously discussed in the literature, the biexponential process can be interpreted as an initial deprotonation step followed by the longer time scale process which separates the resulting ion pair. The results presented here are consistent with some of the previous reports but unambiguously identify and quantitatively measure the Stokes shift as a separate and distinct phenomenon from the deprotonation process, in contrast to other reports that have suggested that all short time (a few picoseconds) dynamics are merely a Stokes shift.

    View details for DOI 10.1021/jp066041k

    View details for Web of Science ID 000243388500006

    View details for PubMedID 17214458

  • Probing dynamics of complex molecular systems with ultrafast 2D IR vibrational echo spectroscopy PHYSICAL CHEMISTRY CHEMICAL PHYSICS Finkelstein, I. J., Zheng, J., Ishikawa, H., Kim, S., Kwak, K., Fayer, M. D. 2007; 9 (13): 1533-1549

    Abstract

    Ultrafast 2D IR vibrational echo spectroscopy is described and a number of experimental examples are given. Details of the experimental method including the pulse sequence, heterodyne detection, and determination of the absorptive component of the 2D spectrum are outlined. As an initial example, the 2D spectrum of the stretching mode of CO bound to the protein myoglobin (MbCO) is presented. The time dependence of the 2D spectrum of MbCO, which is caused by protein structural evolution, is presented and its relationship to the frequency-frequency correlation function is described and used to make protein structural assignments based on comparisons to molecular dynamics simulations. The 2D vibrational echo experiments on the protein horseradish peroxidase are presented. The time dependence of the 2D spectra of the enzyme in the free form and with a substrate bound at the active site are compared and used to examine the influence of substrate binding on the protein's structural dynamics. The application of 2D vibrational echo spectroscopy to the study of chemical exchange under thermal equilibrium conditions is described. 2D vibrational echo chemical exchange spectroscopy is applied to the study of formation and dissociation of organic solute-solvent complexes and to the isomerization around a carbon-carbon single bond of an ethane derivative.

    View details for DOI 10.1039/b618158a

    View details for Web of Science ID 000245633400002

    View details for PubMedID 17429547

  • Confinement or Properties of the Interface? Dynamics of Nanoscopic Water in Reverse Micelles J. Am. Chem. Soc. Moilanen, D. E., Spry, D. B., Levinger, N. E., Fayer, M. D. 2007; 129: 14311 - 14318
  • Ultrafast chemical exchange 2D IR spectroscopy 15th International Conference on Ultrafast Phenomena Zheng, J., Fayer, M. D. SPRINGER-VERLAG BERLIN. 2007: 323–325
  • Ultrafast 2D IR vibrational echo spectroscopy ACCOUNTS OF CHEMICAL RESEARCH Zheng, J., Kwak, K., Fayer, M. D. 2007; 40 (1): 75-83

    Abstract

    The experimental technique and applications of ultrafast two-dimensional infrared (2D IR) vibrational echo spectroscopy are presented. Using ultrashort infrared pulses and optical heterodyne detection to provide phase information, unique information can be obtained about the dynamics, interactions, and structures of molecular systems. The form and time evolution of the 2D IR spectrum permits examination of processes that cannot be studied with linear infrared absorption experiments. Three examples are given: organic solute-solvent complex chemical exchange, dynamics of the hydrogen-bond network of water, and assigning peaks in an IR spectrum of a mixture of species.

    View details for DOI 10.1021/ar068010d

    View details for Web of Science ID 000243683700008

    View details for PubMedID 17226947

  • Phenol-benzene complexation dynamics: Quantum chemistry calculation, molecular dynamics simulations, and two dimensional IR spectroscopy JOURNAL OF CHEMICAL PHYSICS Kwac, K., Lee, C., Jung, Y., Han, J., Kwak, K., Zheng, J., Fayer, M. D., Cho, M. 2006; 125 (24)

    Abstract

    Molecular dynamics (MD) simulations and quantum mechanical electronic structure calculations are used to investigate the nature and dynamics of the phenol-benzene complex in the mixed solvent, benzene/CCl4. Under thermal equilibrium conditions, the complexes are continuously dissociating and forming. The MD simulations are used to calculate the experimental observables related to the phenol hydroxyl stretching mode, i.e., the two dimensional infrared vibrational echo spectrum as a function of time, which directly displays the formation and dissociation of the complex through the growth of off-diagonal peaks, and the linear absorption spectrum, which displays two hydroxyl stretch peaks, one for the complex and one for the free phenol. The results of the simulations are compared to previously reported experimental data and are found to be in quite reasonable agreement. The electronic structure calculations show that the complex is T shaped. The classical potential used for the phenol-benzene interaction in the MD simulations is in good accord with the highest level of the electronic structure calculations. A variety of other features is extracted from the simulations including the relationship between the structure and the projection of the electric field on the hydroxyl group. The fluctuating electric field is used to determine the hydroxyl stretch frequency-frequency correlation function (FFCF). The simulations are also used to examine the number distribution of benzene and CCl4 molecules in the first solvent shell around the phenol. It is found that the distribution is not that of the solvent mole fraction of benzene. There are substantial probabilities of finding a phenol in either a pure benzene environment or a pure CCl4 environment. A conjecture is made that relates the FFCF to the local number of benzene molecules in phenol's first solvent shell.

    View details for DOI 10.1063/1.2403132

    View details for Web of Science ID 000243158000025

    View details for PubMedID 17199356

  • Dynamics of a discotic liquid crystal in the isotropic phase JOURNAL OF CHEMICAL PHYSICS Li, J., Fruchey, K., Fayer, M. D. 2006; 125 (19)

    Abstract

    Optically heterodyne-detected optical Kerr effect (OHD-OKE) experiments are conducted to study the orientational dynamics of a discotic liquid crystal 2,3,6,7,10,11-hexakis(pentyloxy)triphenylene (HPT) in the isotropic phase near the columnar-isotropic (C-I) phase transition. The OHD-OKE signal of HPT is characterized by an intermediate power law t(-0.76+/-0.02) at short times (a few picoseconds), a von Schweidler power law t(-0.26+/-0.01) at intermediate times (hundreds of picoseconds), and an exponential decay at long times (tens of nanoseconds). The exponential decay has Arrhenius temperature dependence. The functional form of the total time dependent decay is identical to the one observed previously for a large number of molecular supercooled liquids. The mode coupling theory schematic model based on the Sjogren [Phys. Rev. A 33, 1254 (1986)] model is able to reproduce the HPT data over a wide range of times from <1 ps to tens of nanoseconds. The studies indicate that the HPT C-I phase transition is a strong first order transition, and the dynamics in the isotropic phase display a complex time dependent profile that is common to other molecular liquids that lack mesoscopic structure.

    View details for DOI 10.1063/1.2378623

    View details for Web of Science ID 000242181800081

    View details for PubMedID 17129161

  • Identification and properties of the L-1(a) and L-1(b) states of pyranine JOURNAL OF CHEMICAL PHYSICS Spry, D. B., Goun, A., Bell, C. B., Fayer, M. D. 2006; 125 (14)

    Abstract

    The spectroscopic locations of the 1La and 1Lb electronic states of pyranine (1-hydroxy-3,6,8-pyrenetrisulfonic acid, commonly referred to as HPTS), as well as several related compounds, are found using magnetic circular dichroism spectroscopy as well as absorption and fluorescence spectroscopies. These electronic states have been discussed in connection with the photoacid properties of HPTS. Polarization selective fluorescence spectroscopy is used to identify the transition dipole directions of the electronic states of the compounds studied. The issue of the origin for the changes in vibronic structure of HPTS in different solvents is addressed. It is demonstrated that a Brownian oscillator model, in which the strength of the coupling of the electronic states to the solvent changes with solvent, is sufficient to reproduce the trends in the shapes of the vibronic structure.

    View details for DOI 10.1063/1.2358685

    View details for Web of Science ID 000241248400047

    View details for PubMedID 17042616

  • Ultrafast two-dimensional infrared vibrational echo chemical exchange experiments and theory JOURNAL OF PHYSICAL CHEMISTRY B Kwak, K., Zheng, J., Cang, H., Fayer, M. D. 2006; 110 (40): 19998-20013

    Abstract

    Ultrafast two-dimensional (2D) infrared vibrational echo experiments and theory are used to examine chemical exchange between solute-solvent complexes and the free solute for the solute phenol and three solvent complex partners, p-xylene, benzene, and bromobenzene, in mixed solvents of the partner and CCl4. The experiments measure the time evolution of the 2D spectra of the hydroxyl (OD) stretching mode of the phenol. The time-dependent 2D spectra are analyzed using time-dependent diagrammatic perturbation theory with a model that includes the chemical exchange (formation and dissociation of the complexes), spectral diffusion of both the complex and the free phenol, orientational relaxation of the complexes and free phenol, and the vibrational lifetimes. The detailed calculations are able to reproduce the experimental results and demonstrate that a method employed previously that used a kinetic model for the volumes of the peaks is adequate to extract the exchange kinetics. The current analysis also yields the spectral diffusion (time evolution of the dynamic line widths) and shows that the spectral diffusion is significantly different for phenol complexes and free phenol.

    View details for DOI 10.1021/jp0624808

    View details for Web of Science ID 000241053400033

    View details for PubMedID 17020388

  • Ultrafast carbon-carbon single-bond rotational isomerization in room-temperature solution SCIENCE Zheng, J., Kwak, K., Xie, J., Fayer, M. D. 2006; 313 (5795): 1951-1955

    Abstract

    Generally, rotational isomerization about the carbon-carbon single bond in simple ethane derivatives in room-temperature solution under thermal equilibrium conditions has been too fast to measure. We achieved this goal using two-dimensional infrared vibrational echo spectroscopy to observe isomerization between the gauche and trans conformations of an ethane derivative, 1-fluoro-2-isocyanato-ethane (1), in a CCl4 solution at room temperature. The isomerization time constant is 43 picoseconds (ps, 10(-12) s). Based on this value and on density functional theory calculations of the barrier heights of 1, n-butane, and ethane, the time constants for n-butane and ethane internal rotation under the same conditions are approximately 40 and approximately 12 ps, respectively.

    View details for DOI 10.1126/science.1132178

    View details for Web of Science ID 000240832200048

    View details for PubMedID 17008529

  • Cytochrome c(552) mutants: Structure and dynamics at the active site probed by multidimensional NMR and vibration echo spectroscopy Festschrift in honor of the 65th Birthday of Robert J Silbey Massari, A. M., McClain, B. L., Finkelstein, I. J., Lee, A. P., Reynolds, H. L., Bren, K. L., Fayer, M. D. AMER CHEMICAL SOC. 2006: 18803–10

    Abstract

    Spectrally resolved infrared stimulated vibrational echo experiments are used to measure the vibrational dephasing of a CO ligand bound to the heme cofactor in two mutated forms of the cytochrome c552 from Hydrogenobacter thermophilus. The first mutant (Ht-M61A) is characterized by a single mutation of Met61 to an Ala (Ht-M61A), while the second variant is doubly modified to have Gln64 replaced by an Asn in addition to the M61A mutation (Ht-M61A/Q64N). Multidimensional NMR experiments determined that the geometry of residue 64 in the two mutants is consistent with a non-hydrogen-bonding and hydrogen-bonding interaction with the CO ligand for Ht-M61A and Ht-M61A/Q64N, respectively. The vibrational echo experiments reveal that the shortest time scale vibrational dephasing of the CO is faster in the Ht-M61A/Q64N mutant than that in Ht-M61A. Longer time scale dynamics, measured as spectral diffusion, are unchanged by the Q64N modification. Frequency-frequency correlation functions (FFCFs) of the CO are extracted from the vibrational echo data to confirm that the dynamical difference induced by the Q64N mutation is primarily an increase in the fast (hundreds of femtoseconds) frequency fluctuations, while the slower (tens of picoseconds) dynamics are nearly unaffected. We conclude that the faster dynamics in Ht-M61A/Q64N are due to the location of Asn64, which is a hydrogen bond donor, above the heme-bound CO. A similar difference in CO ligand dynamics has been observed in the comparison of the CO derivative of myoglobin (MbCO) and its H64V variant, which is caused by the difference in axial residue interactions with the CO ligand. The results suggest a general trend for rapid ligand vibrational dynamics in the presence of a hydrogen bond donor.

    View details for DOI 10.1021/jp054959q

    View details for Web of Science ID 000240654900010

    View details for PubMedID 16986870

  • Dynamics in supercooled ionic organic liquids and mode coupling theory analysis JOURNAL OF PHYSICAL CHEMISTRY A Li, J., Wang, I., Fruchey, K., Fayer, M. D. 2006; 110 (35): 10384-10391

    Abstract

    Optically heterodyne-detected optical Kerr effect experiments are applied to study the orientational dynamics of the supercooled ionic organic liquids N-propyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide (PMPIm) and 1-ethyl-3-methylimidazolium tosylate (EMImTOS). The orientational dynamics are complex with relaxation involving several power law decays followed by a final exponential decay. A mode coupling theory (MCT) schematic model, the Sjögren model, was able to reproduce the PMPIm data very successfully over a wide range of times from 1 ps to hundreds of ns for all temperatures studied. Over the temperature range from room temperature down to the critical temperature Tc of 231 K, the OHD-OKE signal of PMPIm is characterized by the intermediate power law t(-1.00+/-0.04) at short times, a von Schweidler power law t(-0.51+/-0.03) at intermediate times, and a highly temperature-dependent exponential (alpha relaxation) at long times. This form of the decay is identical to the form observed previously for a large number of organic van der Waals liquids. MCT analysis indicates that the theory can explain the experimental data very well for a range of temperatures above Tc, but as might be expected, there are some deviations from the theoretical modeling at temperatures close to Tc. For EMImTOS, the orientational dynamics were studied on the ps time scale in the deeply supercooled region near its glass transition temperature. The orientational relaxation of EMImTOS clearly displays the feature associated with the boson peak at approximately 2 ps, which is the first time domain evidence of the boson peak in ionic organic liquids. Overall, all the dynamical features observed earlier for organic van der Waals liquids using the same experimental technique are also observed for organic ionic liquids.

    View details for DOI 10.1021/jp0637476

    View details for Web of Science ID 000240149200003

    View details for PubMedID 16942043

  • What nonlinear-IR experiments can tell you about water that the IR spectrum cannot JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Piletic, I. R., Moilanen, D. E., Levinger, N. E., Fayer, M. D. 2006; 128 (32): 10366-10367

    Abstract

    Frequently, the IR spectrum of water is used to characterize the structure and strength of the associated hydrogen bond network. Here, we use nonlinear-IR spectroscopy to investigate the dynamics of four aqueous systems that have very similar absorption spectra. We address the question: to what extent can the dynamics of water vary in systems with very similar absorption spectra? The results illustrate that the vibrational lifetimes and orientational relaxation time scales vary dramatically between the four samples and do not correlate with the amount of water relative to surfactant or solute in solution. Nonlinear-IR spectroscopies are therefore important for providing detailed information necessary to understand hydrogen bonded systems.

    View details for DOI 10.1021/ja062549p

    View details for Web of Science ID 000239618700010

    View details for PubMedID 16895392

  • Photoinduced electron transfer and geminate recombination in the group head region of micelles JOURNAL OF CHEMICAL PHYSICS Glusac, K., Goun, A., Fayer, M. D. 2006; 125 (5)

    Abstract

    A pump-probe spectroscopic study of photoinduced forward electron transfer and geminate recombination between donors and acceptors located in the head group regions of micelles is presented. The hole donor is octadecyl-rhodamine B (ODRB) and the hole acceptor is N,N-dimethyl-aniline (DMA). The experiments are conducted as a function of the DMA concentration in the dodecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide micelles. In spite of the fact that the absorptions of both the ODRB radical and ground state bleach spectrally overlap with the ODRB excited state absorption, a procedure that makes it possible to determine the geminate recombination dynamics is presented. These experiments are the first to measure the dynamics of geminate recombination in micelles, and the experiments have two orders of magnitude better time resolution than previous studies of forward transfer. The experimental data are compared to statistical mechanics theoretical calculations of both the forward transfer and the geminate recombination. The theory includes important aspects of the topology of the micelle and the diffusion of the donor-acceptors in the micelle head group region. A semiquantitative but nonquantitative agreement between theory and experiments is achieved.

    View details for DOI 10.1063/1.2227392

    View details for Web of Science ID 000239573100051

    View details for PubMedID 16942246

  • Tracking water's response to structural changes in Nafion membranes JOURNAL OF PHYSICAL CHEMISTRY A Moilanen, D. E., Piletic, I. R., Fayer, M. D. 2006; 110 (29): 9084-9088

    Abstract

    As the water content of Nafion membranes increases, the local environments of water molecules change due to reorganization of the pendant side chains in the hydrophilic domains. Changes in local structure as a function of water content are studied by measuring the IR spectra and the vibrational lifetimes of the hydroxyl stretch of dilute HOD in H(2)O. The main features of the IR spectra are fit well by a weighted sum of the spectra of bulk water and almost dry Nafion, suggesting a two-environment model. An additional small peak on the high frequency side of the main band associated with non-hydrogen-bonded water embedded in the polymer near the interface is analyzed quantitatively as a function of the membrane water content. The spectra of this peak show that a significant reorganization of the interfacial region occurs when the water content of the membrane exceeds the threshold for ion conduction. Vibrational excited state population relaxation times (lifetimes) of the main band lengthen substantially as the water content of the membrane is decreased. The population decays are not single exponentials and indicate that multiple ensembles of water molecules exist, and the characteristics of the individual ensembles change with water content. This is in contrast to the spectra of the main water absorption band, which is only sensitive to two classes of water molecules.

    View details for DOI 10.1021/jp0623084

    View details for Web of Science ID 000239141600009

    View details for PubMedID 16854019

  • Testing the core/shell model of nanoconfined water in reverse micelles using linear and nonlinear IR spectroscopy JOURNAL OF PHYSICAL CHEMISTRY A Piletic, I. R., Moilanen, D. E., Spry, D. B., Levinger, N. E., Fayer, M. D. 2006; 110 (15): 4985-4999

    Abstract

    A core/shell model has often been used to describe water confined to the interior of reverse micelles. The validity of this model for water encapsulated in AOT/isooctane reverse micelles ranging in diameter from 1.7 to 28 nm (w0 = 2-60) and bulk water is investigated using four experimental observables: the hydroxyl stretch absorption spectra, vibrational population relaxation times, orientational relaxation rates, and spectral diffusion dynamics. The time dependent observables are measured with ultrafast infrared spectrally resolved pump-probe and vibrational echo spectroscopies. Major progressive changes appear in all observables as the system moves from bulk water to the smallest water nanopool, w0 = 2. The dynamics are readily distinguishable for reverse micelle sizes smaller than 7 nm in diameter (w0 = 20) compared to the response of bulk water. The results also demonstrate that the size dependent absorption spectra and population relaxation times can be quantitatively predicted using a core-shell model in which the properties of the core (interior of the nanopool) are taken to be those of bulk water and the properties of the shell (water associated with the headgroups) are taken to be those of w0 = 2. A weighted sum of the core and shell components reproduces the size dependent spectra and the nonexponential population relaxation dynamics. However, the same model does not reproduce the spectral diffusion and the orientational relaxation experiments. It is proposed that, when hydrogen bond structural rearrangement is involved (orientational relaxation and spectral diffusion), dynamical coupling between the shell and the core cause the water nanopool to display more homogeneous dynamics. Therefore, the absorption spectra and vibrational lifetime decays can discern different hydrogen bonding environments whereas orientational and spectral diffusion correlation functions predict that the dynamics are size dependent but not as strongly spatially dependent within a reverse micelle.

    View details for DOI 10.1021/jp061065c

    View details for Web of Science ID 000236991900006

    View details for PubMedID 16610816

  • Dynamics of proteins encapsulated in silica sol-gel glasses studied with IR vibrational echo spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Massari, A. M., Finkelstein, I. J., Fayer, M. D. 2006; 128 (12): 3990-3997

    Abstract

    Spectrally resolved infrared stimulated vibrational echo spectroscopy is used to measure the fast dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and -hemoglobin (HbCO) embedded in silica sol-gel glasses. On the time scale of approximately 100 fs to several picoseconds, the vibrational dephasing of the heme-bound CO is measurably slower for both MbCO and HbCO relative to that of aqueous protein solutions. The fast structural dynamics of MbCO, as sensed by the heme-bound CO, are influenced more by the sol-gel environment than those of HbCO. Longer time scale structural dynamics (tens of picoseconds), as measured by the extent of spectral diffusion, are the same for both proteins encapsulated in sol-gel glasses compared to that in aqueous solutions. A comparison of the sol-gel experimental results to viscosity-dependent vibrational echo data taken on various mixtures of water and fructose shows that the sol-gel-encapsulated MbCO exhibits dynamics that are the equivalent of the protein in a solution that is nearly 20 times more viscous than bulk water. In contrast, the HbCO dephasing in the sol-gel reflects only a 2-fold increase in viscosity. Attempts to alter the encapsulating pore size by varying the molar ratio of silane precursor to water (R value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady-state spectroscopic results. The vibrational echo data are discussed in the context of solvent confinement and protein-pore wall interactions to provide insights into the influence of a confined environment on the fast structural dynamics experienced by a biomolecule.

    View details for DOI 10.1021/ja058745y

    View details for Web of Science ID 000236401600049

    View details for PubMedID 16551107

    View details for PubMedCentralID PMC2532503

  • Ultrafast chemical exchange 2-D infrared spectroscopy of complexes in solution 231st National Meeting of the American-Chemical-Society Fayer, M. D., Zheng, J., Kwak, K. AMER CHEMICAL SOC. 2006
  • Formation and dissociation of intra-intermolecular hydrogen-bonded solute-solvent complexes: Chemical exchange two-dimensional infrared vibrational echo spectroscopy JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Zheng, J. R., Kwak, K., Chen, X., Asbury, J. B., Fayer, M. D. 2006; 128 (9): 2977-2987

    Abstract

    2-Methoxyphenol (2MP) solutes form weak complexes with toluene solvent molecules. The complexes are unusual in that the 2MP hydroxyl has an intramolecular hydrogen bond and simultaneously forms an intermolecular hydrogen bond with toluene and other aromatic solvents. In the equilibrated solute-solvent solution, there exists approximately the same concentration of 2MP-toluene complex and free 2MP. The very fast formation and dissociation (chemical exchange) of this type of three-centered hydrogen bond complex were observed in real time under thermal equilibrium conditions with two-dimensional (2D) infrared vibrational echo spectroscopy. Chemical exchange is manifested in the 2D spectrum by the growth of off-diagonal peaks. Both the formation and dissociation can be characterized in terms of the dissociation time constant, which was determined to be 3 ps for the 2MP-toluene complex. The intra-intermolecular hydrogen bond formation is influenced by subtle details of the molecular structure. Although 2MP forms a complex with toluene, it is demonstrated that 2-ethoxyphenol (2EP) does not form complexes to any significant extent. Density functional calculations at the B3LYP/6-31+G(d,p) level suggest that steric effects caused by the extra methyl group in 2EP are responsible for the difference.

    View details for DOI 10.1021/ja057084

    View details for Web of Science ID 000235942000050

    View details for PubMedID 16506778

  • Photoinduced electron transfer and geminate recombination in liquids on short time scales: Experiments and theory JOURNAL OF CHEMICAL PHYSICS Goun, A., Glusac, K., Fayer, M. D. 2006; 124 (8)

    Abstract

    The coupled processes of intermolecular photoinduced forward electron transfer and geminate recombination between the (hole) donor (Rhodamine 3B) and (hole) acceptors (N,N-dimethylaniline) are studied in three molecular liquids: acetonitrile, butyronitrile, and benzonitrile. Two color pump-probe experiments on time scales from approximately 100 fs to hundreds of picoseconds give information about the depletion of the donor excited state due to forward electron transfer and the survival kinetics of the radicals produced by forward electron transfer. The data are analyzed with a model presented previously that includes distance dependent forward and back electron transfer rates, donor and acceptor diffusion, solvent structure, and the hydrodynamic effect in a mean-field theory of through solvent electron transfer. The forward electron transfer is in the normal regime, and the Marcus equation for the distance dependence of the transfer rate is used. The forward electron transfer data for several concentrations in the three solvents are fitted to the theory with a single adjustable parameter, the electronic coupling matrix element Jf at contact. Within experimental error all concentrations in all three solvents are fitted with the same value of Jf. The geminate recombination (back transfer) is in the inverted region, and semiclassical treatment developed by Jortner [J. Chem. Phys. 64, 4860 (1976)] is used to describe the distance dependence of the back electron transfer. The data are fitted with the single adjustable parameter Jb. It is found that the value of Jb decreases as the solvent viscosity increases. Possible explanations are discussed.

    View details for DOI 10.1063/1.2174009

    View details for Web of Science ID 000235663300032

    View details for PubMedID 16512726

  • Three homeotropically aligned nematic liquid crystals: Comparison of ultrafast to slow time-scale dynamics JOURNAL OF CHEMICAL PHYSICS Li, J., WANG, I., Fayer, M. D. 2006; 124 (4)

    Abstract

    The dynamics of two nematic liquid crystals, 4-(trans-4(')-n-octylcyclohexyl)isothiocyanatobenzene and 4-(4-pentyl-cyclohexyl)-benzonitrile, are investigated as a function of temperature both in the homeotropically aligned nematic phase and in the isotropic phase using optical heterodyne-detected optical Kerr effect experiments, which measures the time derivative of the polarizability-polarizability-correlation function (orientational relaxation). Data are presented over a time range of 500 fs-70 micros for the nematic phase and 500 fs to a few hundred nanoseconds for the isotropic phase. The nematic dynamics are compared with a previously studied liquid crystal in the nematic phase. All three liquid crystals have very similar dynamics in the nematic phase that are very different from the isotropic phase. On the slowest time scale (20 ns-70 micros), a temperature-independent power law, the final power law, t(-f) with f approximately 0.5, is observed. On short time scales (approximately 3 ps to approximately 1 ns), a temperature-dependent intermediate power law is observed with an exponent that displays a linear dependence on the nematic order parameter. Between the intermediate power law and the final power law, there is a crossover region that has an inflection point. For times that are short compared to the intermediate power law (approximately <2 ps), the data decay much faster, and can be described as a third power law, although this functional form is not definitive. The isotopic phase data have the same features as found in previous studies of nematogens in the isotropic phase, i.e., the temperature-independent intermediate power law and von Schweidler power law at short to intermediate times, and a highly temperature-dependent long time exponential decay that is well described by the Landau-de Gennes theory. The results show that liquid-crystal dynamics in the nematic phase exhibit universal behavior.

    View details for DOI 10.1063/1.2149867

    View details for Web of Science ID 000234979300070

    View details for PubMedID 16460211

  • A mode coupling theory description of the short- and long-time dynamics of nematogens in the isotropic phase JOURNAL OF CHEMICAL PHYSICS Li, J., Cang, H., ANDERSEN, H. C., Fayer, M. D. 2006; 124 (1)

    Abstract

    Optical heterodyne-detected optical Kerr effect (OHD-OKE) experimental data are pre-sented on nematogens 4-(trans-4-n-octylcyclohexyl)isothiocyanatobenzene (8-CHBT), and 4-(4-pentyl-cyclohexyl)-benzonitrile (5-PCH) in the isotropic phase. The 8-CHBT and 5-PCH data and previously published data on 4-pentyl-4-biphenylcarbonitrile (5-CB) are analyzed using a modification of a schematic mode coupling theory (MCT) that has been successful in describing the dynamics of supercooled liquids. At long time, the OHD-OKE data (orientational relaxation) are well described with the standard Landau-de Gennes (LdG) theory. The data decay as a single exponential. The decay time diverges as the isotropic to nematic phase transition is approached from above. Previously there has been no theory that can describe the complex dynamics that occur at times short compared to the LdG exponential decay. Earlier, it has been noted that the short-time nematogen dynamics, which consist of several power laws, have a functional form identical to that observed for the short time behavior of the orientational relaxation of supercooled liquids. The temperature-dependent orientational dynamics of supercooled liquids have recently been successfully described using a schematic mode coupling theory. The schematic MCT theory that fits the supercooled liquid data does not reproduce the nematogen data within experimental error. The similarities of the nematogen data to the supercooled liquid data are the motivation for applying a modification of the successful MCT theory to nematogen dynamics in the isotropic phase. The results presented below show that the new schematic MCT theory does an excellent job of reproducing the nematogen isotropic phase OHD-OKE data on all time scales and at all temperatures.

    View details for DOI 10.1063/1.2145679

    View details for Web of Science ID 000234428900043

    View details for PubMedID 16409058

  • Vibrational Echo and Pump-Probe Spectroscopic Studies of the Dynamics of Water Molecules Confined to Nanoscopic Dimensions Femtochemistry VII: Fundamental Ultrafast Processes in Chemistry, Physics, and Biology Piletic, I. R., Tan, H. S., Moilanen, D. E., Spry, B., Fayer, M. D., W, C. A., Kimble, J., Eds, M. L. 2006: 195 - 203
  • Comparisons of the Orientational Dynamics of Three Homeotropically Aligned Nematic Liquid Crystals J. Chem. Phys Li, J., Wang, I., Fayer, M. D. 2006; 124
  • Identification and Properties of the 1La and 1Lb States of Pyranine (HPTS) J. Chem. Phys. Spry, D. B., Goun, A., Bell III, C. B., Fayer, M. D. 2006; 125
  • Dynamics of nanoscopic water: Vibrational echo and infrared pump-probe studies of reverse micelles JOURNAL OF PHYSICAL CHEMISTRY B Piletic, I. R., TAN, H. S., Fayer, M. D. 2005; 109 (45): 21273-21284

    Abstract

    The dynamics of water in nanoscopic pools 1.7-4.0 nm in diameter in AOT reverse micelles were studied with ultrafast infrared spectrally resolved stimulated vibrational echo and pump-probe spectroscopies. The experiments were conducted on the OD hydroxyl stretch of low-concentration HOD in the H2O, providing a direct examination of the hydrogen-bond network dynamics. Pump-probe experiments show that the vibrational lifetime of the OD stretch mode increases as the size of the reverse micelle decreases. These experiments are also sensitive to hydrogen-bond dissociation and reformation dynamics, which are observed to change with reverse micelle size. Spectrally resolved vibrational echo data were obtained at several frequencies. The vibrational echo data are compared to data taken on bulk water and on a 6 M NaCl solution, which is used to examine the role of ionic strength on the water dynamics in reverse micelles. Two types of vibrational echo measurements are presented: the vibrational echo decays and the vibrational echo peak shifts. As the water nanopool size decreases, the vibrational echo decays become slower. Even the largest nanopool (4 nm, approximately 1000 water molecules) has dynamics that are substantially slower than bulk water. It is demonstrated that the slow dynamics in the reverse micelle water nanopools are a result of confinement rather than ionic strength. The data are fit using time-dependent diagrammatic perturbation theory to obtain the frequency-frequency correlation function (FFCF) for each reverse micelle. The results are compared to the FFCF of water and show that the largest differences are in the slowest time scale dynamics. In bulk water, the slowest time scale dynamics are caused by hydrogen-bond network equilibration, i.e., the making and breaking of hydrogen bonds. For the smallest nanopools, the longest time scale component of the water dynamics is approximately 10 times longer than the dynamics in bulk water. The vibrational echo data for the smallest reverse micelle displays a dependence on the detection wavelength, which may indicate that multiple ensembles of water molecules are being observed.

    View details for DOI 10.1021/jp051837p

    View details for Web of Science ID 000233280600006

    View details for PubMedID 16853758

  • Photoinduced electron transfer in the head group region of sodium dodecyl sulfate micelles JOURNAL OF LUMINESCENCE Nanda, J., Behera, P. K., Tavernier, H. L., Fayer, M. D. 2005; 115 (3-4): 138-146
  • Accidental vibrational degeneracy in vibrational excited states observed with ultrafast two-dimensional IR vibrational echo spectroscopy JOURNAL OF CHEMICAL PHYSICS Zheng, J. R., Kwak, K., Steinel, T., Asbury, J., Chen, X., Xie, J., Fayer, M. D. 2005; 123 (16)

    Abstract

    The coupling between the OD stretch v=2 level and benzene-ring modes in 2-methoxyphenol-OD (hydroxyl H replaced by D) is observed with ultrafast two-dimensional (2D) IR vibrational echo spectroscopy. Because of this coupling, the 1-2 transition peak in the 2D spectrum is split into a doublet with peaks of approximately equal amplitudes. Several molecules and solvents were used to study this phenomenon. Near-IR (NIR) spectroscopy measurements and density-functional theory calculations (B3LYP6-31+G(d,p) level) were also applied. Experimental results and calculations show that the OD stretch 1-2 transition is coupled to a combination band related to the benzene-ring motions. A simple quantum-mechanical model indicates that the combination band has a frequency of 5172 and 5176.5 cm(-1) in CCl4 and hexane, respectively. The transition between this combination band and the ground state is too weak to detect by NIR. The transition between this band and the OD stretch first excited state is also so weak that most of the intensity of the doublet comes from the oscillator strength produced by coupling to the OD stretch. The model gives the coupling strengths as 6.5 and 7 cm(-1) in CCl4 and hexane, respectively.

    View details for DOI 10.1063/1.2071967

    View details for Web of Science ID 000232855700022

    View details for PubMedID 16268691

  • The influence of aqueous versus glassy solvents on protein dynamics: Vibrational echo experiments and molecular dynamics simulations JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Massari, A. M., Finkelstein, I. J., McClain, B. L., Goj, A., Wen, X., Bren, K. L., Loring, R. F., Fayer, M. D. 2005; 127 (41): 14279-14289

    Abstract

    Spectrally resolved infrared stimulated vibrational echo measurements are used to measure the vibrational dephasing of the CO stretching mode of carbonmonoxy-hemoglobin (HbCO), a myoglobin mutant (H64V), and a bacterial cytochrome c(552) mutant (Ht-M61A) in aqueous solution and trehalose glasses. The vibrational dephasing of the heme-bound CO is significantly slower for all three proteins embedded in trehalose glasses compared to that of aqueous protein solutions. All three proteins exhibit persistent but notably slower spectral diffusion when the protein surface is fixed by the glassy solvent. Frequency-frequency correlation functions (FFCFs) of the CO are extracted from the vibrational echo data to reveal that the structural dynamics, as sensed by the CO, of the three proteins in trehalose and aqueous solution are dominated by fast (tens of femtoseconds), motionally narrowed fluctuations. MD simulations of H64V in dynamic and "static" water are presented as models of the aqueous and glassy environments. FFCFs are calculated from the H64V simulations and qualitatively reproduce the important features of the experimentally extracted FFCFs. The suppression of long time scale (picoseconds to tens of picoseconds) frequency fluctuations (spectral diffusion) in the glassy solvent is the result of a damping of atomic displacements throughout the protein structure and is not limited to structural dynamics that occur only at the protein surface. The analysis provides evidence that some dynamics are coupled to the hydration shell of water, supporting the idea that the bioprotection offered by trehalose is due to its ability to immobilize the protein surface through a thin, constrained layer of water.

    View details for DOI 10.1021/ja053627w

    View details for Web of Science ID 000232605600051

    View details for PubMedID 16218622

  • Ultrafast dynamics of myoglobin without the distal histidine: Stimulated vibrational echo experiments and molecular dynamics simulations JOURNAL OF PHYSICAL CHEMISTRY B Finkelstein, I. J., Goj, A., McClain, B. L., Massari, A. M., Merchant, K. A., Loring, R. F., Fayer, M. D. 2005; 109 (35): 16959-16966

    Abstract

    Ultrafast protein dynamics of the CO adduct of a myoglobin mutant with the polar distal histidine replaced by a nonpolar valine (H64V) have been investigated by spectrally resolved infrared stimulated vibrational echo experiments and molecular dynamics (MD) simulations. In aqueous solution at room temperature, the vibrational dephasing rate of CO in the mutant is reduced by approximately 50% relative to the native protein. This finding confirms that the dephasing of the CO vibration in the native protein is sensitive to the interaction between the ligand and the distal histidine. The stimulated vibrational echo observable is calculated from MD simulations of H64V within a model in which vibrational dephasing is driven by electrostatic forces. In agreement with experiment, calculated vibrational echoes show slower dephasing for the mutant than for the native protein. However, vibrational echoes calculated for H64V do not show the quantitative agreement with measurements demonstrated previously for the native protein.

    View details for DOI 10.1021/jp0517201

    View details for Web of Science ID 000231687400054

    View details for PubMedID 16853158

  • Polarization selective spectroscopy experiments: methodology and pitfalls JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Tan, H. S., Piletic, I. R., Fayer, M. D. 2005; 22 (9): 2009-2017
  • Boson peak in supercooled liquids: Time domain observations and mode coupling theory JOURNAL OF CHEMICAL PHYSICS Cang, H., Li, J., ANDERSEN, H. C., Fayer, M. D. 2005; 123 (6)

    Abstract

    Optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments are presented for the supercooled liquid acetylsalicylic acid (aspirin - ASP). The ASP data and previously published OHD-OKE data on supercooled dibutylphthalate (DBP) display highly damped oscillations with a periods of approximately 2 ps as the temperature is reduced to and below the mode coupling theory (MCT) temperature T(C). The oscillations become more pronounced below T(C). The oscillations can be interpreted as the time domain signature of the boson peak. Recently a schematic MCT model, the Sjogren model, was used to describe the OHD-OKE data for a number of supercooled liquids by Gotze and Sperl [W. Gotze and M. Sperl, Phys. Rev. E 92, 105701 (2004)] , but the short-time and low-temperature behaviors were not addressed. Franosch et al. [T. Franosch, W. Gotze, M. R. Mayr, and A. P. Singh, Phys. Rev. E 55, 3183 (1997)] found that the Sjogren model could describe the boson peak observed by depolarized light-scattering (DLS) experiments on glycerol. The OHD-OKE experiment measures a susceptibility that is a time domain equivalent of the spectrum measured in DLS. Here we present a detailed analysis of the ASP and DBP data over a broad range of times and temperatures using the Sjogren model. The MCT schematic model is able to describe the data very well at all temperatures and relevant time scales. The trajectory of MCT parameters that fit the high-temperature data (no short-time oscillations) when continued below T(C) results in calculations that reproduce the oscillations seen in the data. The results indicate that increasing translational-rotational coupling is responsible for the appearance of the boson peak as the temperature approaches and drops below T(C).

    View details for DOI 10.1063/1.2000235

    View details for Web of Science ID 000231310500043

    View details for PubMedID 16122327

  • Orientational dynamics of water confined on a nanometer length scale in reverse micelles JOURNAL OF CHEMICAL PHYSICS TAN, H. S., Piletic, I. R., Fayer, M. D. 2005; 122 (17)

    Abstract

    The time-resolved orientational anisotropies of the OD hydroxyl stretch of dilute HOD in H(2)O confined on a nanometer length scale in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles are studied using ultrafast infrared polarization and spectrally resolved pump-probe spectroscopy, and the results are compared to the same experiments on bulk water. The orientational anisotropy data for three water nanopool sizes (4.0, 2.4, and 1.7 nm) can be fitted well with biexponential decays. The biexponential decays are analyzed using a wobbling-in-a-cone model that involves fast orientational diffusion within a cone followed by slower, full orientational relaxation. The data provide the cone angles, the diffusion constants for motion within the cones, and the final diffusion constants as a function of the nanopool size. The two processes can be interpreted as a local angular fluctuation of the OD and a global hydrogen bond network rearrangement process. The trend in the relative amplitudes of the long and short exponential decays suggest an increasing rigidity as the nanopool size decreases. The trend in the long decay constants indicates a longer hydrogen bond network rearrangement time with decreasing reverse micelle size. The anisotropy measurements for the reverse micelles studied extrapolate to approximately 0.33 rather than the ideal value of 0.4, suggesting the presence of an initial inertial component in the anisotropy decay that is too fast to resolve. The very fast decay component is consistent with initial inertial orientational motion that is seen in published molecular-dynamics simulations of water in AOT reverse micelles. The angle over which the inertial orientational motion occurs is determined. The results are in semiquantitative agreement with the molecular-dynamics simulations.

    View details for DOI 10.1063/1.1883605

    View details for Web of Science ID 000229064600025

    View details for PubMedID 15910039

  • Ultrafast to slow orientational dynamics of a homeotropically aligned nematic liquid crystal JOURNAL OF PHYSICAL CHEMISTRY B Li, J., WANG, I., Fayer, M. D. 2005; 109 (14): 6514-6519

    Abstract

    The orientational dynamics of a homeotropically aligned nematic liquid crystal, 4'-pentyl-4-biphenylcarbonitrile (5-CB), is studied over more than six decades of time (500 fs to 2 mus) using optical heterodyne detected optical Kerr effect experiments. In contrast to the dynamics of nematogens in the isotropic phase, the data do not decay as a highly temperature-dependent exponential on the longest time scale, but rather, a temperature-independent power law spanning more than two decades of time, the final power law, is observed. On short time scales (approximately 3 ps to approximately 1 ns) another power law, the intermediate power law, is observed that is temperature dependent. The power law exponent of the correlation function associated with the intermediate power law displays a linear dependence on the change in the nematic order parameter with temperature. Between the intermediate power law and the final power law, there is a crossover region that displays an inflection point. The temperature-dependent orientational dynamics in the nematic phase are shown to be very different than those observed in the isotropic phase.

    View details for DOI 10.1021/jp0459581

    View details for Web of Science ID 000228231200009

    View details for PubMedID 16851731

  • Dynamics of water confined on a nanometer length scale in reverse micelles: Ultrafast infrared vibrational echo spectroscopy PHYSICAL REVIEW LETTERS TAN, H. S., Piletic, I. R., Riter, R. E., Levinger, N. E., Fayer, M. D. 2005; 94 (5)

    Abstract

    The dynamics of water, confined on a nanometer length scale (1.7 to 4.0 nm) in sodium bis-(2-ethylhexyl) sulfosuccinate reverse micelles, is directly investigated using frequency resolved infrared vibrational echo experiments. The data are compared to bulk water and salt solution data. The experimentally determined frequency-frequency correlation functions show that the confined water dynamics is substantially slower than bulk water dynamics and is size dependent. The fastest dynamics (approximately 50 fs) is more similar to bulk water, while the slowest time scale dynamics is much slower than water, and, in analogy to bulk water, reflects the making and breaking of hydrogen bonds.

    View details for DOI 10.1103/PhysRevLett.94.057405

    View details for Web of Science ID 000226941500083

    View details for PubMedID 15783696

  • Dynamics of water probed with vibrational echo correlation spectroscopy JOURNAL OF CHEMICAL PHYSICS Asbury, J. B., Steinel, T., Kwak, K., Corcelli, S. A., Lawrence, C. P., Skinner, J. L., Fayer, M. D. 2004; 121 (24): 12431-12446

    Abstract

    Vibrational echo correlation spectroscopy experiments on the OD stretch of dilute HOD in H(2)O are used to probe the structural dynamics of water. A method is demonstrated for combining correlation spectra taken with different infrared pulse bandwidths (pulse durations), making it possible to use data collected from many experiments in which the laser pulse properties are not identical. Accurate measurements of the OD stretch anharmonicity (162 cm(-1)) are presented and used in the data analysis. In addition, the recent accurate determination of the OD vibrational lifetime (1.45 ps) and the time scale for the production of vibrational relaxation induced broken hydrogen bond "photoproducts" ( approximately 2 ps) aid in the data analysis. The data are analyzed using time dependent diagrammatic perturbation theory to obtain the frequency time correlation function (FTCF). The results are an improved FTCF compared to that obtained previously with vibrational echo correlation spectroscopy. The experimental data and the experimentally determined FTCF are compared to calculations that employ a polarizable water model (SPC-FQ) to calculate the FTCF. The SPC-FQ derived FTCF is much closer to the experimental results than previously tested nonpolarizable water models which are also presented for comparison.

    View details for DOI 10.1063/1.1818107

    View details for Web of Science ID 000225714500036

    View details for PubMedID 15606264

  • Watching hydrogen bonds break: A transient absorption study of water JOURNAL OF PHYSICAL CHEMISTRY A Steinel, T., Asbury, J. B., Zheng, J. R., Fayer, M. D. 2004; 108 (50): 10957-10964

    View details for DOI 10.1021/jp046711r

    View details for Web of Science ID 000225694900006

  • Dynamics of hemoglobin in human erythrocytes and in solution: Influence of viscosity studied by ultrafast vibrational echo experiments JOURNAL OF THE AMERICAN CHEMICAL SOCIETY McClain, B. L., Finkelstein, I. J., Fayer, M. D. 2004; 126 (48): 15702-15710

    Abstract

    Ultrafast spectrally resolved stimulated vibrational echo experiments are used to measure the vibrational dephasing of the CO stretching mode of hemoglobin-CO (HbCO) inside living human erythrocytes (red blood cells), in liquid solutions, and in a glassy matrix. A method is presented to overcome the adverse impact on the vibrational echo signal from the strong light scattering caused by the cells. The results from the cytoplasmic HbCO are compared to experiments on aqueous HbCO samples prepared in different buffers, solutions containing low and high concentrations of glycerol, and in a solid trehalose matrix. Measurements are also presented that provide an accurate determination of the viscosity at the very high Hb concentration that is found inside the cells. It is demonstrated that the dynamics of the protein, as sensed by the CO ligand, are the same inside the erythrocytes and in aqueous solution and are independent of the viscosity. In solutions that are predominantly glycerol, the dynamics are modified somewhat but are still independent of viscosity. The experiments in trehalose give the dynamics at infinite viscosity and are used to separate the viscosity-dependent dynamics from the viscosity-independent dynamics. Although the HbCO dynamics are the same in the red blood cell and in the equivalent aqueous solutions, differences in the absorption spectra show that the distribution of a protein's equilibrium substates is sensitive to small pH differences.

    View details for DOI 10.1021/ja0454790

    View details for Web of Science ID 000225505700020

    View details for PubMedID 15571392

  • Spectral diffusion in a fluctuating charge model of water JOURNAL OF CHEMICAL PHYSICS Corcelli, S. A., Lawrence, C. P., Asbury, J. B., Steinel, T., Fayer, M. D., Skinner, J. L. 2004; 121 (18): 8897-8900

    Abstract

    We apply the combined electronic structure/molecular dynamics approach of Corcelli, Lawrence, and Skinner [J. Chem. Phys. 120, 8107 (2004)] to the fluctuating charge (SPC-FQ) model of liquid water developed by Rick, Stuart, and Berne [J. Chem. Phys. 101, 6141 (1994)]. For HOD in H(2)O the time scale for the long-time decay of the OD stretch frequency time-correlation function, which corresponds to the time scale for hydrogen-bond rearrangement in the liquid, is about 1.5 ps. This result is significantly longer than the 0.9 ps decay previously calculated for the nonpolarizable SPC/E water model. Our results for the SPC-FQ model are in better agreement with recent vibrational echo experiments.

    View details for DOI 10.1063/1.1803532

    View details for Web of Science ID 000224798900026

    View details for PubMedID 15527354

  • Photoinduced intermolecular electron transfer in liquid solutions JOURNAL OF PHYSICAL CHEMISTRY A Saik, V. O., Goun, A. A., Nanda, J., Shirota, K., Tavernier, H. L., Fayer, M. D. 2004; 108 (32): 6696-6703

    View details for DOI 10.1021/jp049391k

    View details for Web of Science ID 000223182700012

  • Vibrational echo experiments on red blood cells: Comparison of the dynamics of cytoplasmic and aqueous hemoglobin CHEMICAL PHYSICS LETTERS McClain, B. L., Finkelstein, I. J., Fayer, M. D. 2004; 392 (4-6): 324-329
  • Fifth-order contributions to ultrafast spectrally resolved vibrational echoes: Heme-CO proteins JOURNAL OF CHEMICAL PHYSICS Finkelstein, I. J., McClain, B. L., Fayer, M. D. 2004; 121 (2): 877-885

    Abstract

    The fifth order contributions to the signals of ultrafast infrared spectrally resolved stimulated vibrational echoes at high intensities have been investigated in carbonmonoxy heme proteins. High intensities are often required to obtain good data. Intensity dependent measurements are presented on hemoglobin-CO (Hb-CO) and a mutant of myoglobin, H64V-CO. The spectrally resolved vibrational echoes demonstrate that fifth order effects arise at both the 1-0 and the 2-1 emission frequencies of the stretching mode of the CO chromophore bound at the active site of heme proteins. Unlike one-dimensional experiments, in which the signal is integrated over all emission frequencies, spectrally resolving the signal shows that the fifth order contributions have a much more pronounced influence on the 2-1 transition than on the 1-0 transition. By spectrally isolating the 1-0 transition, the influence of fifth order contributions to vibrational echo data can be substantially reduced. Analysis of fifth order Feynman diagrams that contribute in the vibrational echo phase-matched direction demonstrates the reason for the greater influence of fifth order processes on the 1-2 transition, and that the fifth order contributions are heterodyne amplified by the third order signal. Finally, it is shown that the anharmonic oscillations in vibrational echo data of Hb-CO that previous work had attributed strictly to fifth order effects arise even without fifth order contributions.

    View details for DOI 10.1063/1.1758940

    View details for Web of Science ID 000222265600033

    View details for PubMedID 15260618

  • Hydrogen bond networks: Structure and evolution after hydrogen bond breaking JOURNAL OF PHYSICAL CHEMISTRY B Asbury, J. B., Steinel, T., Fayer, M. D. 2004; 108 (21): 6544-6554

    View details for DOI 10.1021/jp036600c

    View details for Web of Science ID 000221546200005

  • Photoinduced electron transfer and geminate recombination for photoexcited acceptors in a pure donor solvent JOURNAL OF CHEMICAL PHYSICS Saik, V. O., Goun, A. A., Fayer, M. D. 2004; 120 (20): 9601-9611

    Abstract

    Photoinduced electron transfer and geminate recombination are studied for the systems rhodamine 3B (R3B(+)) and rhodamine 6G (R6G(+)), which are cations, in neat neutral N,N-dimethylaniline (DMA). Following photoexcitation of R3B(+) or R6G(+) (abbreviated as R(+)), an electron is transferred from DMA to give the neutral radical R and the cation DMA(+). Because the DMA hole acceptor is the neat solvent, the forward transfer rate is very large, approximately 5x10(12) s(-1). The forward transfer is followed by geminate recombination, which displays a long-lived component suggesting several percent of the radicals escape geminate recombination. Spectrally resolved pump-probe experiments are used in which the probe is a "white" light continuum, and the full time-dependent spectrum is recorded with a spectrometer/charge-coupled device. Observations of stimulated emission (excited state decay-forward electron transfer), the R neutral radical spectrum, and the DMA(+) radical cation spectrum as well as the ground-state bleach recovery (geminate recombination) make it possible to unambiguously follow the electron transfer kinetics. Theoretical modeling shows that the long-lived component can be explained without invoking hole hopping or spin-forbidden transitions.

    View details for DOI 10.1063/1.1712826

    View details for Web of Science ID 000221268300020

    View details for PubMedID 15267972

  • Vibrational echo correlation spectroscopy probes of hydrogen bond dynamics in water and methanol 8th International Meeting on Hole Burning Single Molecule, and Related Spectroscopies Asbury, J. B., Steinel, T., Fayer, M. D. ELSEVIER SCIENCE BV. 2004: 271–86
  • Water dynamics: dependence on local structure probed with vibrational echo correlation spectroscopy CHEMICAL PHYSICS LETTERS Steinel, T., Asbury, J. B., Corcelli, S. A., Lawrence, C. P., Skinner, J. L., Fayer, M. D. 2004; 386 (4-6): 295-300
  • Water dynamics: Vibrational echo correlation spectroscopy and comparison to molecular dynamics simulations JOURNAL OF PHYSICAL CHEMISTRY A Asbury, J. B., Steinel, T., Stromberg, C., Corcelli, S. A., Lawrence, C. P., Skinner, J. L., Fayer, M. D. 2004; 108 (7): 1107-1119

    View details for DOI 10.1021/jp036266k

    View details for Web of Science ID 000188957600002

  • Vibrational Echo Correlation Spectroscopy: a New Probe of Hydrogen Bond Dynamics in Water and Methanol Femtosecond Laser Spectroscopy: Progress in Lasers Asbury, J. B., Steinel, T., Fayer, M. D. edited by Hannaford, P. Kluwer, Brussells. 2004
  • Orientational dynamics of the ionic organic liquid 1-ethyl-3-methylimidazolium nitrate JOURNAL OF CHEMICAL PHYSICS Cang, H., Li, J., Fayer, M. D. 2003; 119 (24): 13017-13023

    View details for DOI 10.1063/1.1628668

    View details for Web of Science ID 000187576300037

  • Hydrogen bond breaking probed with multidimensional stimulated vibrational echo correlation spectroscopy JOURNAL OF CHEMICAL PHYSICS Asbury, J. B., Steinel, T., Stromberg, C., Gaffney, K. J., Piletic, I. R., Fayer, M. D. 2003; 119 (24): 12981-12997

    View details for DOI 10.1063/1.1627762

    View details for Web of Science ID 000187576300033

  • Hydrogen bond dynamics probed with ultrafast infrared heterodyne-detected multidimensional vibrational stimulated echoes PHYSICAL REVIEW LETTERS Asbury, J. B., Steinel, T., Stromberg, C., Gaffney, K. J., Piletic, I. R., Goun, A., Fayer, M. D. 2003; 91 (23)

    Abstract

    Hydrogen bond dynamics are explicated with exceptional detail using multidimensional infrared vibrational echo correlation spectroscopy with full phase information. Probing the hydroxyl stretch of methanol-OD oligomers in CCl4, the dynamics of the evolving hydrogen bonded network are measured with ultrashort (<50 fs) pulses. The data along with detailed model calculations demonstrate that vibrational relaxation leads to selective hydrogen bond breaking on the red side of the spectrum (strongest hydrogen bonds) and the production of singly hydrogen bonded photoproducts.

    View details for DOI 10.1103/PhysRevLett.91.237402

    View details for Web of Science ID 000187004500053

    View details for PubMedID 14683215

  • Dynamical signature of two "ideal glass transitions" in nematic liquid crystals JOURNAL OF CHEMICAL PHYSICS Cang, H., Li, J., Novikov, V. N., Fayer, M. D. 2003; 119 (19): 10421-10427

    View details for DOI 10.1063/1.1618215

    View details for Web of Science ID 000186273200053

  • Myoglobin-CO substate structures and dynamics: Multidimensional vibrational echoes and molecular dynamics simulations JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Merchant, K. A., Noid, W. G., Akiyama, R., Finkelstein, I. J., Goun, A., McClain, B. L., Loring, R. F., Fayer, M. D. 2003; 125 (45): 13804-13818

    Abstract

    Spectrally resolved infrared stimulated vibrational echo data were obtained for sperm whale carbonmonoxymyoglobin (MbCO) at 300 K. The measured dephasing dynamics of the CO ligand are in agreement with dephasing dynamics calculated with molecular dynamics (MD) simulations for MbCO with the residue histidine-64 (His64) having its imidazole epsilon nitrogen protonated (N(epsilon)-H). The two conformational substate structures B(epsilon) and R(epsilon) observed in the MD simulations are assigned to the spectroscopic A(1) and A(3) conformational substates of MbCO, respectively, based on the agreement between the experimentally measured and calculated dephasing dynamics for these substates. In the A(1) substate, the N(epsilon)-H proton and N(delta) of His64 are approximately equidistant from the CO ligand, while in the A(3) substate, the N(epsilon)-H of His64 is oriented toward the CO, and the N(delta) is on the surface of the protein. The MD simulations show that dynamics of His64 represent the major source of vibrational dephasing of the CO ligand in the A(3) state on both femtosecond and picosecond time scales. Dephasing in the A(1) state is controlled by His64 on femtosecond time scales, and by the rest of the protein and the water solvent on longer time scales.

    View details for DOI 10.1021/ja035654x

    View details for Web of Science ID 000186424800045

    View details for PubMedID 14599220

  • Using ultrafast infrared multidimensional correlation spectroscopy to aid in vibrational spectral peak assignments CHEMICAL PHYSICS LETTERS Asbury, J. B., Steinel, T., Fayer, M. D. 2003; 381 (1-2): 139-146
  • Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning studies of spectral diffusion JOURNAL OF CHEMICAL PHYSICS Piletic, I. R., Gaffney, K. J., Fayer, M. D. 2003; 119 (1): 423-434

    View details for DOI 10.1063/1.1578058

    View details for Web of Science ID 000183585400049

  • Ultrafast heterodyne detected infrared multidimensional vibrational stimulated echo studies of hydrogen bond dynamics CHEMICAL PHYSICS LETTERS Asbury, J. B., Steinel, T., Stromberg, C., Gaffney, K. J., Piletic, I. R., Goun, A., Fayer, M. D. 2003; 374 (3-4): 362-371
  • Dynamics in supercooled liquids and in the isotropic phase of liquid crystals: A comparison JOURNAL OF CHEMICAL PHYSICS Cang, H., Li, J., Novikov, V. N., Fayer, M. D. 2003; 118 (20): 9303-9311

    View details for DOI 10.1063/1.1568338

    View details for Web of Science ID 000182794300030

  • Experimental observation of a nearly logarithmic decay of the orientational correlation function in supercooled liquids on the picosecond-to-nanosecond time scales PHYSICAL REVIEW LETTERS Cang, H., Novikov, V. N., Fayer, M. D. 2003; 90 (19)

    Abstract

    Dynamics of five supercooled molecular liquids have been studied using optical heterodyne detected optical Kerr effect experiments. "Intermediate" time scale power law decays (approximately 2 ps to 1-10 ns) with temperature independent exponents close to -1 have been observed in all five samples from high temperature to approximately T(c), the mode-coupling theory (MCT) critical temperature. The amplitude of the intermediate power law increases with temperature as [(T-T(c))/T(c)](1/2). The results cannot be explained by standard MCT, and one possible explanation within MCT would require the higher order singularity scenario, thought to be highly improbable, to be virtually universal.

    View details for DOI 10.1103/PhysRevLett.90.197401

    View details for Web of Science ID 000182928300050

    View details for PubMedID 12785982

  • Hydrogen bond dynamics in alcohols. 225th National Meeting of the American-Chemical-Society Fayer, M. D., Gaffney, K. J., Piletic, I. R. AMER CHEMICAL SOC. 2003: U467–U467
  • Logarithmic decay of the orientational correlation function in supercooled liquids on the Ps to Ns time scale JOURNAL OF CHEMICAL PHYSICS Cang, H., Novikov, V. N., Fayer, M. D. 2003; 118 (6): 2800-2807

    View details for DOI 10.1063/1.1536612

    View details for Web of Science ID 000180564800038

  • Orientational relaxation and vibrational excitation transfer in methanol-carbon tetrachloride solutions JOURNAL OF CHEMICAL PHYSICS Gaffney, K. J., Piletic, I. R., Fayer, M. D. 2003; 118 (5): 2270-2278

    View details for DOI 10.1063/1.1534580

    View details for Web of Science ID 000180579900030

  • Isomerization and intermolecular solute-solvent interactions of ethyl isocyanate: Ultrafast infrared vibrational echoes and linear vibrational spectroscopy JOURNAL OF CHEMICAL PHYSICS Levinger, N. E., Davis, P. H., Behera, P. K., Myers, D. J., Stromberg, C., Fayer, M. D. 2003; 118 (3): 1312-1326

    View details for DOI 10.1063/1.1527926

    View details for Web of Science ID 000180316700037

  • Structural assignments and dynamics of the A substates of MbCO: Spectrally resolved vibrational echo experiments and molecular dynamics simulations JOURNAL OF PHYSICAL CHEMISTRY B Merchant, K. A., Noid, W. G., Thompson, D. E., Akiyama, R., Loring, R. F., Fayer, M. D. 2003; 107 (1): 4-7

    View details for DOI 10.1021/jp026793o

    View details for Web of Science ID 000180254900002

  • Experimental Observation of Nearly Logarithmic Decay of the Orientational Correlation Function in Supercooled Liquids on the Ps to Ns Time Scale Phys. Rev. Lett. Cang, H., Novikov, V. N., Fayer, M. D. 2003; 90 (197401)
  • Hydrogen bond dissociation and reformation in methanol oligomers following hydroxyl stretch relaxation JOURNAL OF PHYSICAL CHEMISTRY A Gaffney, K. J., Davis, P. H., Piletic, I. R., Levinger, N. E., Fayer, M. D. 2002; 106 (50): 12012-12023

    View details for DOI 10.1021/jp.021696g

    View details for Web of Science ID 000179921000004

  • Short time dynamics in the isotropic phase of liquid crystals: the aspect ratio and the power law decay CHEMICAL PHYSICS LETTERS Cang, H., Li, H., Fayer, M. D. 2002; 366 (1-2): 82-87
  • Hydrogen bond breaking and reformation in alcohol oligomers following vibrational relaxation of a non-hydrogen-bond donating hydroxyl stretch JOURNAL OF PHYSICAL CHEMISTRY A Gaffney, K. J., Piletic, I. R., Fayer, M. D. 2002; 106 (41): 9428-9435

    View details for DOI 10.1021/jp021170w

    View details for Web of Science ID 000178548500007

  • Frequency selected ultrafast infrared vibrational echo studies of liquids, glasses, and proteins JOURNAL OF PHYSICAL CHEMISTRY A Merchant, K. A., Xu, Q. H., Thompson, D. E., Fayer, M. D. 2002; 106 (38): 8839-8849

    View details for DOI 10.1021/jp021145q

    View details for Web of Science ID 000178106300002

  • Temperature-dependent vibrational dephasing: Comparison of liquid and glassy solvents using frequency-selected vibrational echoes JOURNAL OF CHEMICAL PHYSICS Xu, Q. H., Fayer, M. D. 2002; 117 (6): 2732-2740

    View details for DOI 10.1063/1.1492280

    View details for Web of Science ID 000177042800032

  • Vibrational dynamics of a metalloporphyrin carbonyl in liquid and glass solutions: Ultrafast 1-D and frequency-selected vibrational echo experiments LASER PHYSICS Xu, Q. H., Fayer, M. D. 2002; 12 (8): 1104-1113
  • Influence of diffusion on the kinetics of donor-acceptor electron transfer monitored by the quenching of donor fluorescence JOURNAL OF PHYSICAL CHEMISTRY A Gladkikh, V. S., Burshtein, A. I., Tavernier, H. L., Fayer, M. D. 2002; 106 (30): 6982-6990

    View details for DOI 10.1021/jp0207228

    View details for Web of Science ID 000177104700010

  • Myoglobin-CO conformational substate dynamics: 2D vibrational echoes and MD simulations BIOPHYSICAL JOURNAL Merchant, K. A., Thompson, D. E., Xu, Q. H., Williams, R. B., Loring, R. F., Fayer, M. D. 2002; 82 (6): 3277-3288

    Abstract

    Two-dimensional (2D) infrared vibrational echoes were performed on horse heart carbonmonoxymyoglobin (MbCO) in water over a range of temperatures. The A(1) and A(3) conformational substates of MbCO are found to have different dephasing rates with different temperature dependences. A frequency-frequency correlation function derived from molecular dynamics simulations on MbCO at 298 K is used to calculate the vibrational echo decay. The calculated decay shows substantial agreement with the experimentally measured decays. The 2D vibrational echo probes protein dynamics and provides an observable that can be used to test structural assignments for the MbCO conformational substates.

    View details for PubMedID 12023251

  • Comparison of the ultrafast to slow time scale dynamics of three liquid crystals in the isotropic phase JOURNAL OF CHEMICAL PHYSICS Gottke, S. D., Cang, H., Bagchi, B., Fayer, M. D. 2002; 116 (14): 6339-6347

    View details for DOI 10.1063/1.1462039

    View details for Web of Science ID 000174634200048

  • Exploring relaxation and hydrogen bond breaking in methanol-d oligomers in carbon tetrachloride. Levinger, N. E., Davis, P. H., Fayer, M. D. AMER CHEMICAL SOC. 2002: C62–C62
  • Separation of contributions to the third-order signal: ultrafast frequency-selected vibrational echo experiments on a metalloporphyrin-CO CHEMICAL PHYSICS LETTERS Xu, Q. H., Thompson, D. E., Merchant, K. A., Fayer, M. D. 2002; 355 (1-2): 139-146
  • Vibrational dynamics of large hot molecules in the collisionless gas phase JOURNAL OF CHEMICAL PHYSICS Stromberg, C., Myers, D. J., Fayer, M. D. 2002; 116 (9): 3540-3553

    View details for DOI 10.1063/1.1446850

    View details for Web of Science ID 000173888400004

  • Thermal, structural, and orientational relaxation of supercooled salol studied by polarization-dependent impulsive stimulated scattering JOURNAL OF CHEMICAL PHYSICS Glorieux, C., Nelson, K. A., Hinze, G., Fayer, M. D. 2002; 116 (8): 3384-3395

    View details for DOI 10.1063/1.1445749

    View details for Web of Science ID 000173853600026

  • Accidental degeneracy beats: A distinct type of beat phenomenon in nonlinear optical spectroscopy PHYSICAL REVIEW A Merchant, K. A., Thompson, D. E., Fayer, M. D. 2002; 65 (2)
  • Orientational dynamics of the glass forming liquid, dibutylphthalate: Time domain experiments and comparison to mode coupling theory JOURNAL OF CHEMICAL PHYSICS Brace, D. D., Gottke, S. D., Cang, H., Fayer, M. D. 2002; 116 (4): 1598-1606
  • Liquid crystal dynamics in the isotropic phase JOURNAL OF CHEMICAL PHYSICS Gottke, S. D., Brace, D. D., Cang, H., Bagchi, B., Fayer, M. D. 2002; 116 (1): 360-367
  • Comparison of the Ultrafast to Slow Timescale Dynamics of Three Liquid Crystals in the Isotropic Phase J. Chem. Phys. Gottke, S. D., Cang, H., Bagchi, B., Fayer, M. D. 2002; 116: 6339-6347
  • Separation of Contributions to the Third-Order Vibrational Echo Signal: Ultrafast Frequency-Selected Experiments on a Metalloporphyrin-CO Chem. Phys. Lett. Xu, Q., Thompson, D. E., Merchant, K. A., Fayer, M. D. 2002; 355: 139-146
  • Vibrational relaxation of the free terminal hydroxyl stretch in methanol oligomers: Indirect pathway to hydrogen bond breaking JOURNAL OF CHEMICAL PHYSICS Levinger, N. E., Davis, P. H., Fayer, M. D. 2001; 115 (20): 9352-9360
  • Dynamic partitioning of an aromatic probe between the headgroup and core regions of cationic micelles JOURNAL OF PHYSICAL CHEMISTRY B Cang, H., Brace, D. D., Fayer, M. D. 2001; 105 (41): 10007-10015

    View details for DOI 10.1021/jp0113127

    View details for Web of Science ID 000171614900016

  • Photoinduced intermolecular electron transfer in micelles: Dielectric and structural properties of micelle headgroup regions JOURNAL OF PHYSICAL CHEMISTRY A Tavernier, H. L., Laine, F., Fayer, M. D. 2001; 105 (39): 8944-8957

    View details for DOI 10.1021/jp0106597

    View details for Web of Science ID 000171401200016

  • Temperature and density dependent solute vibrational relaxation in supercritical fluoroform JOURNAL OF CHEMICAL PHYSICS Myers, D. J., Shigeiwa, M., Cherayil, B. J., Fayer, M. D. 2001; 115 (10): 4689-4695
  • Two-dimensional ultrafast infrared vibrational echo studies of solute-solvent interactions and dynamics JOURNAL OF CHEMICAL PHYSICS Thompson, D. E., Merchant, K. A., Fayer, M. D. 2001; 115 (1): 317-330
  • Solute-solvent interactions: two-dimensional ultrafast infrared vibrational echo experiments CHEMICAL PHYSICS LETTERS Thompson, D. E., Merchant, K. A., Fayer, M. D. 2001; 340 (3-4): 267-274
  • Vibrational dephasing of carbonmonoxy myoglobin JOURNAL OF PHYSICAL CHEMISTRY B Williams, R. B., Loring, R. F., Fayer, M. D. 2001; 105 (19): 4068-4071

    View details for DOI 10.1021/jp010798o

    View details for Web of Science ID 000168803800005

  • Two-dimensional time-frequency ultrafast infrared vibrational echo spectroscopy PHYSICAL REVIEW LETTERS Merchant, K. A., Thompson, D. E., Fayer, M. D. 2001; 86 (17): 3899-3902

    Abstract

    2D spectrally resolved ultrafast (<200 fs) IR vibrational echo experiments were performed on Rh(CO)(2)acac [(acetylacetonato)dicarbonylrhodium (I)]. The 2D spectra display features that reflect the 0-1 and 1-2 transitions and the combination band transition of the symmetric (S) and antisymmetric (A) CO stretching modes. Three oscillations in the data arise from the frequency difference between the S and A modes (quantum beats) and the S and A anharmonicities. A new explanation is given for these "anharmonic" oscillations. Calculations show that spectral resolution enables the 0-1 and 1-2 dephasing to be measured independently.

    View details for Web of Science ID 000168338300051

    View details for PubMedID 11329352

  • Solute-solute spatial distribution in hydrogen bonding liquids probed with time-dependent intermolecular electron transfer JOURNAL OF CHEMICAL PHYSICS Tavernier, H. L., Fayer, M. D. 2001; 114 (10): 4552-4564
  • Effects of solvent viscosity on protein dynamics: Infrared vibrational echo experiments and theory JOURNAL OF PHYSICAL CHEMISTRY B Rector, K. D., Jiang, J. W., Berg, M. A., Fayer, M. D. 2001; 105 (5): 1081-1092
  • Time domain optical studies of dynamics in supercooled o-terphenyl: Comparison to mode coupling theory on fast and slow time scales JOURNAL OF PHYSICAL CHEMISTRY B Gottke, S. D., Brace, D. D., Hinze, G., Fayer, M. D. 2001; 105 (1): 238-245
  • Fast protein dynamics probed with infrared vibrational echo experiments ANNUAL REVIEW OF PHYSICAL CHEMISTRY Fayer, M. D. 2001; 52: 315-356

    Abstract

    IR vibrational echo experiments are used to study dynamics in myoglobin (Mb) by investigating the dephasing of the CO-stretching mode of CO bound at the active site of the protein (Mb-CO). The temperature dependence and the viscosity dependence of Mb-CO pure dephasing have been measured in several solvents. In low-temperature, glassy solvents, the pure dephasing has a power law temperature dependence, T(1.3), that reflects glasslike protein dynamics. In liquids, the temperature dependence is much steeper and arises from a combination of pure temperature dependence and the influence of decreasing solvent viscosity with increasing temperature. As the solvent viscosity decreases, the ability of the protein's surface to undergo topological fluctuations increases, which in turn increases the internal protein-structural fluctuations. The protein-structural motions are coupled to the CO bound at the active site by electric field fluctuations that accompany movements of polar residues. The dynamic electric field-coupling mechanism is tested by observing differences in the temperature dependence of the pure dephasing of Mb-CO mutations.

    View details for Web of Science ID 000169246500014

    View details for PubMedID 11326068

  • Elements of Quantum Mechanics Fayer, M. D. Oxford University Press, New York. 2001
  • Dynamic Partitioning of an Aromatic Probe Between the Head Group and Core Regions of Cationic Micelles J. Phys. Chem. B Cang, H., Brace, D. D., Fayer, M. D. 2001; 105: 10007-10015
  • Ultrafast Infrared and Raman Spectroscopy Fayer, M. D. Marcel Dekker, New York. 2001
  • Time Domain Optical Studies of Dynamics in Supercooled Ortho-terphenyl: Comparison to Mode Coupling Theory on Fast and Slow Time Scales J. Phys. Chem. Gottke, S. D., Brace, D. D., Hinze, G., Fayer, M. D. 2001; 105: 238-245
  • Photoinduced Intermolecular Electron Transfer in Micelles: Dielectric and Structural Properties of Micelle Head Group Regions J. Phys. Chem. A Tavernier, H. L., Laine, F., Fayer, M. D. 2001; 105: 8944-8957
  • Vibrational Relaxation of Polyatomic Molecules in Supercritical Fluids and the Gas Phase Ultrafast Infrared and Raman Spectroscopy Myers, D. J., Shigeiwa, M., Fayer, M. D., Cherayil, B. J. edited by Fayer, M. D. Marcel Dekker: New York. 2001: 625–674
  • Infrared Vibrational Echo Experiments Ultrafast Infrared and Raman Spectroscopy, Rector, K. D., Fayer, M. edited by Fayer, M. D. Marcel Dekker: New York. 2001: 227–272
  • Photoinduced intermolecular electron transfer in complex liquids: Experiment and theory JOURNAL OF CHEMICAL PHYSICS Tavernier, H. L., Kalashnikov, M. M., Fayer, M. D. 2000; 113 (22): 10191-10201
  • Distance dependence of electron transfer in DNA: The role of the reorganization energy and free energy JOURNAL OF PHYSICAL CHEMISTRY B Tavernier, H. L., Fayer, M. D. 2000; 104 (48): 11541-11550

    View details for DOI 10.1021/jp001362w

    View details for Web of Science ID 000165725700015

  • A detailed test of mode-coupling theory on all time scales: Time domain studies of structural relaxation in a supercooled liquid JOURNAL OF CHEMICAL PHYSICS Hinze, G., Brace, D. D., Gottke, S. D., Fayer, M. D. 2000; 113 (9): 3723-3733
  • Two-pulse echo experiments in the spectral diffusion regime JOURNAL OF CHEMICAL PHYSICS Berg, M. A., Rector, K. D., Fayer, M. D. 2000; 113 (8): 3233-3242
  • Temperature dependence of solute vibrational relaxation in supercritical fluids: experiment and theory CHEMICAL PHYSICS LETTERS Myers, D. J., Shigeiwa, M., Stromberg, C., Fayer, M. D., Cherayil, B. J. 2000; 325 (5-6): 619-626
  • Vibrational lifetimes and spectral shifts in supercritical fluids as a function of density: Experiments and theory JOURNAL OF PHYSICAL CHEMISTRY B Myers, D. J., Shigeiwa, M., Fayer, M. D., Cherayil, B. J. 2000; 104 (10): 2402-2414
  • Orientational dynamics in supercooled liquids near T-c and comparison with ideal mode-coupling theory PHYSICAL REVIEW LETTERS Hinze, G., Brace, D. D., Gottke, S. D., Fayer, M. D. 2000; 84 (11): 2437-2440
  • Dynamics in globular proteins: vibrational echo experiments CHEMICAL PHYSICS LETTERS Rector, K. D., Thompson, D. E., Merchant, K., Fayer, M. D. 2000; 316 (1-2): 122-128
  • Orientational dynamics in supercooled liquids near T(c) and comparison with ideal mode-coupling theory Physical review letters Hinze, G., Brace, D. D., Gottke, S. D., Fayer, M. D. 2000; 84 (11): 2437–40

    Abstract

    Orientational dynamics in supercooled salol and ortho-terphenyl were measured near their critical temperatures, T(c), with optical Kerr effect experiments spanning a very broad range of times. Above T(c), the decays are shown to be in excellent agreement with the master curve predicted by ideal mode-coupling theory when higher order terms are included. Between the critical decay and the von Schweidler power laws, the intermediate time range of the data can be modeled by a power law. This intermediate power law, located at 2

    View details for PubMedID 11018904

  • Orientational Dynamics in Supercooled Liquids Near Tc and Comparison to Ideal Mode Coupling Theory Phys. Rev. Lett. Hinze, G., Brace, D. D., Gottke, S. D., Fayer, M. D. 2000; 84: 2437-2440
  • Density dependent vibrational relaxation in supercritical fluids CHEMICAL PHYSICS LETTERS Myers, D. J., Shigeiwa, M., Fayer, M. D., Cherayil, B. J. 1999; 313 (3-4): 592-599
  • Non-exponential relaxation of a single quantum vibrational excitation of a large molecule in collision free gas phase at elevated temperature CHEMICAL PHYSICS LETTERS Myers, D. J., Shigeiwa, M., Fayer, M. D., Silbey, R. 1999; 312 (5-6): 399-406
  • Phase separation in binary and ternary polymer composites studied with electronic excitation transport MACROMOLECULES Hussey, D. M., Fayer, M. D. 1999; 32 (20): 6638-6645
  • Translational-rotational coupling in supercooled liquids: Heterodyne detected density induced molecular alignment JOURNAL OF CHEMICAL PHYSICS Hinze, G., Francis, R. S., Fayer, M. D. 1999; 111 (6): 2710-2719
  • T-2 selective scanning vibrational echo spectroscopy CHEMICAL PHYSICS LETTERS Rector, K. D., Fayer, M. D., Engholm, J. R., Crosson, E., Smith, T. I., Schwettman, H. A. 1999; 305 (1-2): 51-56
  • Density-induced heterodyne-amplified rotational dynamics: a new technique for studying orientational relaxation CHEMICAL PHYSICS LETTERS Francis, R. S., Hinze, G., Fayer, M. D. 1999; 304 (1-2): 28-34
  • A dynamical transition in the protein myoglobin observed by infrared vibrational echo experiments JOURNAL OF PHYSICAL CHEMISTRY A Rector, K. D., Engholm, J. R., Rella, C. W., Hill, J. R., Dlott, D. D., Fayer, M. D. 1999; 103 (14): 2381-2387
  • Crack propagation induced heating in crystalline energetic materials JOURNAL OF CHEMICAL PHYSICS Holmes, W., Francis, R. S., Fayer, M. D. 1999; 110 (7): 3576-3583
  • Nitro group asymmetric stretching mode lifetimes of molecules used in energetic materials CHEMICAL PHYSICS LETTERS Aubuchon, C. M., Rector, K. D., Holmes, W., Fayer, M. D. 1999; 299 (1): 84-90
  • T2 Selective Scanning Vibrational Echo Spectroscopy Chem. Phys. Lett. Rector, K. D., Fayer, M. D., Engholm, J. R., Crosson, E., Smith, T. I., Schwettman, H. A. 1999; 305: 51-56
  • Myoglobin dynamics measured with vibrational echo experiments 8th International Conference on Time-Resolved Vibrational Spectroscopy Rector, K. D., Fayer, M. D. TAYLOR & FRANCIS LTD. 1999: 19–34
  • Monte Carlo simulations of electronic excitation transfer in polymer composites and comparison to theory JOURNAL OF CHEMICAL PHYSICS Hussey, D. M., Matzinger, S., Fayer, M. D. 1998; 109 (19): 8708-8718
  • Temperature dependent vibrational lifetimes in supercritical fluids near the critical point JOURNAL OF CHEMICAL PHYSICS Myers, D. J., Chen, S., Shigeiwa, M., Cherayil, B. J., Fayer, M. D. 1998; 109 (14): 5971-5979
  • Vibrational echo spectroscopy: Spectral selectivity from vibrational coherence JOURNAL OF CHEMICAL PHYSICS Rector, K. D., Zimdars, D., Fayer, M. D. 1998; 109 (13): 5455-5465
  • Fluorescent probe solubilization in the headgroup and core regions of micelles: Fluorescence lifetime and orientational relaxation measurements JOURNAL OF PHYSICAL CHEMISTRY B Matzinger, S., Hussey, D. M., Fayer, M. D. 1998; 102 (37): 7216-7224
  • Polystyrene size determination in polystyrene and poly(vinyl methyl ether) using electronic excitation transport JOURNAL OF PHYSICAL CHEMISTRY B Diachun, N. A., Hussey, D. M., Fayer, M. D. 1998; 102 (37): 7112-7119
  • Myoglobin's ultrafast dynamics measured with vibrational echo experiments International Symposium on Free Electron Laser Facilities and Applications (FELFA 98) Rector, K. D., Fayer, M. D. ELSEVIER SCIENCE BV. 1998: 218–24
  • Solvent reorganization energy and free energy change for donor/acceptor electron transfer at micelle surfaces: Theory and experiment JOURNAL OF PHYSICAL CHEMISTRY B Tavernier, H. L., Barzykin, A. V., Tachiya, M., Fayer, M. D. 1998; 102 (31): 6078-6088
  • Vibrational echoes: a new approach to condensed-matter vibrational spectroscopy INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY Rector, K. D., Fayer, M. D. 1998; 17 (3): 261-306
  • Vibrational dynamics of polyatomic molecules in polyatomic supercritical fluids near the critical point. Fayer, M. D., Urdahl, R. S., Myers, D. J., Rector, K. D., Davis, P. H., Cherayil, B. J. AMER CHEMICAL SOC. 1998: U148–U148
  • Vibrational dephasing mechanisms in liquids and glasses: Vibrational echo experiments JOURNAL OF CHEMICAL PHYSICS Rector, K. D., Fayer, M. D. 1998; 108 (5): 1794-1803
  • Dynamics of myoglobin-CO with the proximal histidine removed: Vibrational echo experiments JOURNAL OF PHYSICAL CHEMISTRY B Rector, K. D., Engholm, J. R., Hill, J. R., Myers, D. J., Hu, R., Boxer, S. G., Dlott, D. D., Fayer, M. D. 1998; 102 (2): 331-333
  • Polystyrene Size Determination in Polystyrene and Polyvinylmethylether Using Electronic Excitation Transport J. Phys. Chem. B Diachun, N. A., Hussey, D. M., Fayer, M. D. 1998; 102: 7112-7119
  • Vibrational echo studies of proteins, liquids, and glasses Conference on Laser Techniques for Condensed-Phase and Biological Systems Rector, K. D., Fayer, M. D. SPIE-INT SOC OPTICAL ENGINEERING. 1998: 34–45
  • Vibrational Echoes: A New Approach to Condensed Mater Vibrational Spectroscopy Internat. Rev. Phys. Chem. Rector, K. D., Fayer, M. D. 1998; 17: 261-306
  • Temperature dependence of vibrational lifetimes at the critical density in supercritical mixtures JOURNAL OF CHEMICAL PHYSICS Myers, D. J., Urdahl, R. S., Cherayil, B. J., Fayer, M. D. 1997; 107 (23): 9741-9748
  • Vibrational relaxation in supercritical fluids near the critical point JOURNAL OF CHEMICAL PHYSICS Cherayil, B. J., Fayer, M. D. 1997; 107 (19): 7642-7650
  • Photoinduced electron transfer on the surfaces of micelles JOURNAL OF PHYSICAL CHEMISTRY B Weidemaier, K., Tavernier, H. L., Fayer, M. D. 1997; 101 (45): 9352-9361
  • Photoinduced electron transfer between donors and acceptors on micelle surfaces CHEMICAL PHYSICS LETTERS Weidemaier, K., Tavernier, H. L., Chu, K. T., Fayer, M. D. 1997; 276 (5-6): 309-315
  • Effect of chromophore diffusion on electronic excitation transfer in micellar systems CHEMICAL PHYSICS LETTERS Matzinger, S., Weidemaier, K., Fayer, M. D. 1997; 276 (3-4): 274-281
  • Vibrational echo studies of pure dephasing: Mechanisms in liquids and glasses CHEMICAL PHYSICS LETTERS Rector, K. D., KWOK, A. S., Ferrante, C., Francis, R. S., Fayer, M. D. 1997; 276 (3-4): 217-223
  • Vibrational lifetimes and vibrational line positions in polyatomic supercritical fluids near the critical point JOURNAL OF CHEMICAL PHYSICS Urdahl, R. S., Myers, D. J., Rector, K. D., Davis, P. H., Cherayil, B. J., Fayer, M. D. 1997; 107 (10): 3747-3757
  • Vibrational anharmonicity and multilevel vibrational dephasing from vibrational echo beats JOURNAL OF CHEMICAL PHYSICS Rector, K. D., KWOK, A. S., Ferrante, C., Tokmakoff, A., Rella, C. W., Fayer, M. D. 1997; 106 (24): 10027-10036
  • Electronic dephasing in nonpolar room temperature liquids: UV photon echo pulse duration dependent measurements JOURNAL OF CHEMICAL PHYSICS Zimdars, D., Francis, R. S., Ferrante, C., Fayer, M. D. 1997; 106 (18): 7498-7511
  • Temperature-dependent vibrational and orientational relaxation of monocarbonyls in polyatomic solvents. Davis, P. H., Aubuchon, C. M., Fayer, M. D. AMER CHEMICAL SOC. 1997: 117-PHYS
  • Photoinduced electron transfer and geminate recombination in liquids JOURNAL OF PHYSICAL CHEMISTRY A Weidemaier, K., Tavernier, H. L., Swallen, S. F., Fayer, M. D. 1997; 101 (10): 1887-1902
  • Mutant and wild-type myoglobin-CO protein dynamics: Vibrational echo experiments JOURNAL OF PHYSICAL CHEMISTRY B Rector, K. D., Rella, C. W., Hill, J. R., KWOK, A. S., Sligar, S. G., Chien, E. Y., Dlott, D. D., Fayer, M. D. 1997; 101 (8): 1468-1475
  • Vibrational Echo Studies of Heme Protein Dynamics ACS Symp. Ser. Fayer, M. D., Dlott, D. D. edited by Foukas, J. T., Kivelson, D., Mohanty, U., Nelson, K. A. 1997: 337–50
  • Vibrational echo studies of heme-protein dynamics Symposium on Supercooled Liquids - Advances and Novel Applications, at the 212th National Meeting of the American-Chemical-Society Fayer, M. D., Dlott, D. D. AMER CHEMICAL SOC. 1997: 324–337
  • Electronic Dephasing of a Non-polar Solute in Non-polar Liquids: UV Femtosecond Photon Echo Pulse Duration Dependent Measurements J. Chem. Phys. Zimdars, D., Francis, R. S., Ferrante, C., Fayer, M. D. 1997; 106: 7498-7511
  • Electronic excitation transfer as a probe of phase behavior in polymer composites Conference on Advances in Fluorescence Sensing Technology III Hussey, D. M., Keller, L., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1997: 446–452
  • Vibrational relaxation of a polyatomic solute in a polyatomic supercritical fluid near the critical point JOURNAL OF CHEMICAL PHYSICS Urdahl, R. S., Rector, K. D., Myers, D. J., Davis, P. H., Fayer, M. D. 1996; 105 (19): 8973-8976
  • Tuning the vibrational relaxation of CO bound to heme and metalloporphyrin complexes JOURNAL OF PHYSICAL CHEMISTRY Hill, J. R., Ziegler, C. J., Suslick, K. S., Dlott, D. D., Rella, C. W., Fayer, M. D. 1996; 100 (46): 18023-18032
  • Vibrational echo studies of myoglobin-CO JOURNAL OF PHYSICAL CHEMISTRY Rella, C. W., Rector, K. D., Kwok, A., Hill, J. R., Schwettman, H. A., Dlott, D. D., Fayer, M. D. 1996; 100 (38): 15620-15629
  • Vibrational relaxation in metalloporphyrin CO complexes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Dlott, D. D., Fayer, M. D., Hill, J. R., Rella, C. W., Suslick, K. S., Ziegler, C. J. 1996; 118 (33): 7853-7854
  • Vibrational echo studies of protein dynamics PHYSICAL REVIEW LETTERS Rella, C. W., Kwok, A., RECTOR, K., Hill, J. R., Schwettman, H. A., Dlott, D. D., Fayer, M. D. 1996; 77 (8): 1648-1651
  • Vibrational dynamics of carbon monoxide at the active sites of mutant heme proteins JOURNAL OF PHYSICAL CHEMISTRY Hill, J. R., Dlott, D. D., Rella, C. W., Peterson, K. A., Decatur, S. M., Boxer, S. G., Fayer, M. D. 1996; 100 (29): 12100-12107
  • Photophysical studies of probes bound to cross-link junctions in poly(dimethyl siloxane) elastomers and nanocomposites 3rd International Symposium on Functional Dyes (FUNCTIONAL DYE 95) Leezenberg, P. B., Fayer, M. D., Frank, C. W. INT UNION PURE APPLIED CHEMISTRY. 1996: 1381–88
  • Calculations of electronic excitation transfer: Applications to ordered phases in polymeric materials JOURNAL OF PHYSICAL CHEMISTRY Keller, L., Hussey, D. M., Fayer, M. D. 1996; 100 (24): 10257-10264
  • Experimental and theoretical analysis of photoinduced electron transfer: Including the role of liquid structure JOURNAL OF PHYSICAL CHEMISTRY Swallen, S. F., Weidemaier, K., Tavernier, H. L., Fayer, M. D. 1996; 100 (20): 8106-8117
  • Rotational dynamics of naphthalene-labeled cross-link junctions in poly(dimethylsiloxane) elastomers JOURNAL OF PHYSICAL CHEMISTRY Leezenberg, P. B., Marcus, A. H., Frank, C. W., Fayer, M. D. 1996; 100 (18): 7646-7655
  • Electronic spectral diffusion in glasses: The influence of coupling to the medium on experimental observables JOURNAL OF CHEMICAL PHYSICS Zimdars, D., Fayer, M. D. 1996; 104 (11): 3865-3875
  • Role of diffusion in photoinduced electron transfer on a micelle surface: Theoretical and Monte Carlo investigations JOURNAL OF PHYSICAL CHEMISTRY Weidemaier, K., Fayer, M. D. 1996; 100 (9): 3767-3774
  • Solvent structure and hydrodynamic effects in photoinduced electron transfer JOURNAL OF CHEMICAL PHYSICS Swallen, S. F., Weidemaier, K., Fayer, M. D. 1996; 104 (8): 2976-2986
  • Theory of electronic excitation transfer in polymer micelles and lamellae 7th International Conference on Unconventional Photoactive Systems Hussey, D. M., Keller, L., Fayer, M. D. GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP. 1996: 173–177
  • Temperature-dependent vibrational dynamics and inhomogeneous broadening in glass-forming liquids studied with infrared photon echoes 9th International Symposium on Ultrafast Processes in Spectroscopy (UPS 95) Tokmakoff, A., Fayer, M. D. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1996: 123–125
  • Vibrational population dynamics in liquids and glasses - IR pump-probe experiments from 10 K to 300 K 9th International Symposium on Ultrafast Processes in Spectroscopy (UPS 95) Ferrante, C., Tokmakoff, A., TAITI, C., KWOK, A. S., Francis, R. S., Rector, K. D., Fayer, M. D. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1996: 115–117
  • Rotational Dynamics of Naphthalene-Labeled Cross-link Junctions of Varying Functionality in Poly(dimethylsiloxane) Elastomers J. Phys. Chem. Leezenberg, P. B., Marcus, A. H., Frank, C. W., Fayer, M. D. 1996; 100: 7646-7655
  • Liquid, glass, and protein vibrational dynamics: Infrared vibrational echo experiments Proceedings of the Fifth International Meeting on Hole Burning and Related Spectroscopies (HBRS'96) - Science and Applications Rector, K. D., Fayer, M. D. GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP. 1996: 1–9
  • Nanodomain formation and phase separation in polymer blends Fluorescence Detection IV Conference Hussey, D. M., Keller, L., Diachun, N. A., Marcus, A. H., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1996: 136–142
  • Chromophore rich nanodomains in bulk and ultra thin film polymer blends 7th International Conference on Unconventional Photoactive Systems Marcus, A. H., Morkved, T., Jaeger, H., Rice, S. A., Hussey, D. M., Diachun, N. A., Fayer, M. D. GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP. 1996: 31–35
  • Ultrafast infrared spectroscopy in biomolecules: Active site dynamics of heme proteins 7th International Conference on Time Resolved Vibrational Spectroscopy (TRVS-7) Hill, J. R., Dlott, D. D., Rella, C. W., Smith, T. I., Schwettman, H. A., Peterson, K. A., Kwok, A., Rector, K. D., Fayer, M. D. JOHN WILEY & SONS LTD. 1996: 277–99
  • PHOTOINDUCED ELECTRON-TRANSFER AND GEMINATE RECOMBINATION IN LIQUIDS - ANALYTICAL THEORY AND MONTE-CARLO SIMULATIONS JOURNAL OF CHEMICAL PHYSICS Swallen, S. F., Fayer, M. D. 1995; 103 (20): 8864-8872
  • NANODOMAIN FORMATION IN A LIQUID POLYMER BLEND - THE INITIAL-STAGES OF PHASE-SEPARATION JOURNAL OF CHEMICAL PHYSICS Marcus, A. H., Hussey, D. M., Diachun, N. A., Fayer, M. D. 1995; 103 (18): 8189-8200
  • INFRARED PHOTON-ECHO EXPERIMENTS - EXPLORING VIBRATIONAL DYNAMICS IN LIQUIDS AND GLASSES ACCOUNTS OF CHEMICAL RESEARCH Tokmakoff, A., Fayer, M. D. 1995; 28 (11): 437-445
  • VIBRATIONAL-RELAXATION OF CARBON-MONOXIDE IN MODEL HEME COMPOUNDS - 6-COORDINATE METALLOPORPHYRINS (M=FE, RU, OS) CHEMICAL PHYSICS LETTERS Hill, J. R., Dlott, D. D., Fayer, M. D., Peterson, K. A., Rella, C. W., Rosenblatt, M. M., Suslick, K. S., Ziegler, C. J. 1995; 244 (3-4): 218-223
  • INFRARED VIBRATIONAL PHOTON-ECHO EXPERIMENTS IN LIQUIDS AND GLASSES JOURNAL OF PHYSICAL CHEMISTRY Tokmakoff, A., Zimdars, D., Urdahl, R. S., Francis, R. S., KWOK, A. S., Fayer, M. D. 1995; 99 (36): 13310-13320
  • THE LOW-FREQUENCY DENSITY-OF-STATES AND VIBRATIONAL POPULATION-DYNAMICS OF POLYATOMIC-MOLECULES IN LIQUIDS JOURNAL OF CHEMICAL PHYSICS Moore, P., Tokmakoff, A., Keyes, T., Fayer, M. D. 1995; 103 (9): 3325-3334
  • HOMOGENEOUS VIBRATIONAL DYNAMICS AND INHOMOGENEOUS BROADENING IN GLASS-FORMING LIQUIDS - INFRARED PHOTON-ECHO EXPERIMENTS FROM ROOM-TEMPERATURE TO 10 K JOURNAL OF CHEMICAL PHYSICS Tokmakoff, A., Fayer, M. D. 1995; 103 (8): 2810-2826
  • VIBRATIONAL DYNAMICS OF LIQUIDS AND GLASSES PROBED WITH IR PHOTON-ECHOES International Workshop on Laser Physics (LPHYS-94) Tokmakoff, A., KOWK, A., Urdahl, R., Zimdars, D. A., Francis, R., Fayer, M. D. INTERPERIODICA. 1995: 652–55
  • VIBRATIONAL DYNAMICS IN CONDENSED MATTER PROBED WITH LINAC BASED FELS 16th International Free Electron Laser Conference Tokmakoff, A., KOWK, A., URHDAL, R., Zimdars, D. A., Fayer, M. D. ELSEVIER SCIENCE BV. 1995: 540–43
  • MULTILEVEL VIBRATIONAL DEPHASING AND VIBRATIONAL ANHARMONICITY FROM INFRARED PHOTON-ECHO BEATS CHEMICAL PHYSICS LETTERS Tokmakoff, A., KWOK, A. S., Urdahl, R. S., Francis, R. S., Fayer, M. D. 1995; 234 (4-6): 289-295
  • VIBRATIONAL SPECTRAL DIFFUSION AND POPULATION-DYNAMICS IN A GLASS-FORMING LIQUID - VARIABLE BANDWIDTH PICOSECOND INFRARED-SPECTROSCOPY JOURNAL OF CHEMICAL PHYSICS Tokmakoff, A., Urdahl, R. S., Zimdars, D., Francis, R. S., KWOK, A. S., Fayer, M. D. 1995; 102 (10): 3919-3931
  • THEORY OF UNIVERSAL FAST ORIENTATIONAL DYNAMICS IN THE ISOTROPIC-PHASE OF LIQUID-CRYSTALS JOURNAL OF CHEMICAL PHYSICS Sengupta, A., Fayer, M. D. 1995; 102 (10): 4193-4202
  • PHOTOINDUCED ELECTRON-TRANSFER AND GEMINATE RECOMBINATION ON A MICELLE SURFACE - ANALYTICAL THEORY AND MONTE-CARLO SIMULATIONS JOURNAL OF CHEMICAL PHYSICS Weidemaier, K., Fayer, M. D. 1995; 102 (9): 3820-3829
  • EXCLUDED-VOLUME EFFECTS IN PHOTOINDUCED ELECTRON-TRANSFER AND GEMINATE RECOMBINATION - ANALYTICAL THEORY AND SIMULATIONS JOURNAL OF PHYSICAL CHEMISTRY Swallen, S. F., Weidemaier, K., Fayer, M. D. 1995; 99 (7): 1856-1866
  • Vibrational Dynamics in Liquids and Glasses Probed with Infrared Photon Echoes Using a Free Electron Laser Zimdars, D., Tokmakoff, A., Sauter, B., Francis, R. S., Kwok, A. S., Fayer, M. D. edited by Barbara, P. F., Knox, W. H., Mourou, G. A., Zewail, A. H., 1995: 58–62
  • Vibrational Dynamics in Condensed Matter Probed with Linac Based FELs Nuclear Instruments & Methods in Physics Research A Tokmakoff, A., Kwok, A. S., Urdahl, R. S., Zimdars, D. A., Fayer, M. D. 1995; 358: 550-553
  • Vibrational Dynamics at the Active Site of Myoglobin: Picosecond Infrared Free Electron Laser Experiments Peterson, K. A., Hill, J. R., Tokmakoff, A., Sauter, B., Zimdars, D., Dlott, D. D., Fayer, M. D. edited by Barbara, P. F., Knox, W. H., Mourou, G. A., Zewail, A. H. 1995: 445–47
  • Local Order and Ultrafast Molecular Dynamics in Liquids: Subpicosecond Transient Grating Optical Kerr Effect Experiments Sengupta, A., Fayer, M. D. edited by Barbara, P. F., Knox, W. H., Mourou, G. A., Zewail, A. H. 1995: 97–98
  • THEORY OF VIBRATIONAL-RELAXATION OF POLYATOMIC-MOLECULES IN LIQUIDS JOURNAL OF CHEMICAL PHYSICS Kenkre, V. M., Tokmakoff, A., Fayer, M. D. 1994; 101 (12): 10618-10629
  • VIBRATIONAL DYNAMICS OF CARBON-MONOXIDE AT THE ACTIVE-SITE OF MYOGLOBIN - PICOSECOND INFRARED FREE-ELECTRON LASER PUMP-PROBE EXPERIMENTS JOURNAL OF PHYSICAL CHEMISTRY Hill, J. R., Tokmakoff, A., Peterson, K. A., Sauter, B., Zimdars, D., Dlott, D. D., Fayer, M. D. 1994; 98 (43): 11213-11219
  • VIBRATIONAL PHOTON-ECHOES IN A LIQUID AND GLASS - ROOM-TEMPERATURE TO 10-K JOURNAL OF CHEMICAL PHYSICS Tokmakoff, A., Zimdars, D., Sauter, B., Francis, R. S., KWOK, A. S., Fayer, M. D. 1994; 101 (2): 1741-1744
  • INTERMOLECULAR STRUCTURE IN A SINGLE-COMPONENT POLYMER GLASS - TOWARDS HIGH-RESOLUTION MEASUREMENTS OF THE SIDE-CHAIN PAIR CORRELATION-FUNCTION JOURNAL OF CHEMICAL PHYSICS Marcus, A. H., Fayer, M. D., Curro, J. G. 1994; 100 (12): 9156-9169
  • TEMPERATURE-DEPENDENT VIBRATIONAL-RELAXATION IN POLYATOMIC LIQUIDS - PICOSECOND INFRARED PUMP-PROBE EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Tokmakoff, A., Sauter, B., Fayer, M. D. 1994; 100 (12): 9035-9043
  • PHONON-INDUCED SCATTERING BETWEEN VIBRATIONS AND MULTIPHOTON VIBRATIONAL UP-PUMPING IN LIQUID SOLUTION CHEMICAL PHYSICS LETTERS Tokmakoff, A., Sauter, B., KWOK, A. S., Fayer, M. D. 1994; 221 (5-6): 412-418
  • DYNAMICS IN POLYDIMETHYLSILOXANE - THE EFFECT OF SOLUTE POLARITY JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Diachun, N. A., Marcus, A. H., Hussey, D. M., Fayer, M. D. 1994; 116 (3): 1027-1032
  • ULTRAFAST NONEXPONENTIAL DYNAMICS IN A POLYMER GLASS-FORMING LIQUID JOURNAL OF CHEMICAL PHYSICS Sengupta, A., Fayer, M. D. 1994; 100 (2): 1673-1683
  • EFFECTS OF LOCAL LIQUID STRUCTURE ON ORIENTATIONAL RELAXATION - 2-ETHYLNAPHTHALENE, NEAT AND IN SOLUTION JOURNAL OF PHYSICAL CHEMISTRY Greenfield, S. R., Sengupta, A., Stankus, J. J., Terazima, M., Fayer, M. D. 1994; 98 (1): 313-320
  • Local Order and Ultrafast dynamics in Liquids Transient Grating Optical Kerr Effect Experiments Sengupta, A., Fayer, M. D. edited by Rizzo, T., Myers, A. John Wiley & Sons, New York. 1994: 211–282
  • PICOSECOND VIBRATIONAL PHOTON-ECHO EXPERIMENTS IN LIQUIDS AND GLASSES Conference on Longer Wavelength Lasers and Applications Zimdars, D., Tokmakoff, A., Sauter, B., Chen, S., KWOK, A. S., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1994: 26–34
  • MOLECULAR-ENERGY TRANSFER IN CONDENSED MATTER STUDIED BY ULTRAFAST VIBRATIONAL SPECTROSCOPY Conference on Longer Wavelength Lasers and Applications Hill, J. R., Chen, S., Dlott, D. D., Tokmakoff, A., Sauter, B., Zimdars, D., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1994: 75–84
  • Phonon Induced Scattering Between Vibrations and Multiphoton Up-pumping in Liquid Solution Chem. Phys. Lett. Tokmakoff, A., Sauter, B., Kwok, A. S., Fayer, M. D. 1994; 221: 412-418
  • Electron Transfer in Solution: Theory and Experiment Ultrafast Spectroscopy of Chemical Systems Fayer, M. D., Song, L., Swallen, S. E., Dorfman, R. C., Weidemaier, K. edited by John, S. Kluwer Academic Publishers. 1994: 37–80
  • STRUCTURE OF COMPLEX-SYSTEMS USING ELECTRONIC EXCITATION TRANSPORT - THEORY, MONTE-CARLO SIMULATIONS, AND EXPERIMENTS ON MICELLE SOLUTIONS JOURNAL OF CHEMICAL PHYSICS FINGER, K. U., Marcus, A. H., Fayer, M. D. 1994; 100 (1): 271-286
  • INFLUENCE OF LOCAL LIQUID STRUCTURE ON ORIENTATIONAL DYNAMICS - ISOTROPIC-PHASE OF LIQUID-CRYSTALS JOURNAL OF PHYSICAL CHEMISTRY Stankus, J. J., Torre, R., Fayer, M. D. 1993; 97 (37): 9478-9487
  • OPTICAL PARAMETRIC AMPLIFICATION OF 1-KHZ HIGH-ENERGY PICOSECOND MIDINFRARED PULSES AND APPLICATION TO INFRARED TRANSIENT-GRATING EXPERIMENTS ON DIAMOND JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Tokmakoff, A., Marshall, C. D., Fayer, M. D. 1993; 10 (9): 1785-1791
  • INTERMOLECULAR STRUCTURE IN A POLYMER GLASS - ELECTRONIC EXCITATION TRANSFER STUDIES MACROMOLECULES Marcus, A. H., Diachun, N. A., Fayer, M. D. 1993; 26 (12): 3041-3048
  • TRANSIENT GRATING DIFFRACTION FROM AN INTERFACE BETWEEN 2 MATERIALS - THEORY AND EXPERIMENTAL APPLICATION JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Fishman, I. M., Marshall, C. D., Tokmakoff, A., Fayer, M. D. 1993; 10 (6): 1006-1016
  • DYNAMICS OF IONIC LIPOPHILIC PROBES IN MICELLES - PICOSECOND FLUORESCENCE DEPOLARIZATION MEASUREMENTS JOURNAL OF PHYSICAL CHEMISTRY Quitevis, E. L., Marcus, A. H., Fayer, M. D. 1993; 97 (21): 5762-5769
  • EXTRA RESONANCES IN TIME-DOMAIN 4-WAVE-MIXING OPTICS LETTERS Fourkas, J. T., Trebino, R., Dugan, M. A., Fayer, M. D. 1993; 18 (10): 781-783

    Abstract

    We show that extra resonances, such as those caused in frequency-domain nonlinear wave mixing by pure dephasing or laser fluctuations, can also be induced by operation in the time domain. These pulse-length-induced extra resonances arise in transient-grating experiments when the laser pulses are short enough that a steady state cannot be achieved during the excitation process. We show theoretically that these resonances increase in strength with decreasing excitation pulse length until the pulse length becomes shorter than the dephasing time of the medium and quote an experimental example to support this interpretation.

    View details for Web of Science ID A1993LA94700009

    View details for PubMedID 19802271

  • PICOSECOND INFRARED VIBRATIONAL PHOTON-ECHOES IN A LIQUID AND GLASS USING A FREE-ELECTRON LASER PHYSICAL REVIEW LETTERS Zimdars, D., Tokmakoff, A., Chen, S., Greenfield, S. R., Fayer, M. D., Smith, T. I., Schwettman, H. A. 1993; 70 (18): 2718-2721
  • CHEMICAL-REACTION INITIATION AND HOT-SPOT FORMATION IN SHOCKED ENERGETIC MOLECULAR MATERIALS JOURNAL OF PHYSICAL CHEMISTRY Tokmakoff, A., Fayer, M. D., Dlott, D. D. 1993; 97 (9): 1901-1913
  • FLAME TEMPERATURE-MEASUREMENT USING PICOSECOND TRANSIENT GRATING EXPERIMENTS CHEMICAL PHYSICS LETTERS Brewer, T. R., Fourkas, J. T., Fayer, M. D. 1993; 203 (4): 344-348
  • PHOTOINDUCED ELECTRON-TRANSFER AND GEMINATE RECOMBINATION IN SOLUTION JOURNAL OF PHYSICAL CHEMISTRY Song, L., Swallen, S. F., DORFMAN, R. C., Weidemaier, K., Fayer, M. D. 1993; 97 (7): 1374-1382
  • THERMAL-BOUNDARY RESISTANCE AND DIFFUSIVITY MEASUREMENTS ON THIN YBA2CU3O7-X FILMS WITH MGO AND SRTIO3 SUBSTRATES USING THE TRANSIENT GRATING METHOD JOURNAL OF APPLIED PHYSICS Marshall, C. D., Tokmakoff, A., Fishman, I. M., Eom, C. B., Phillips, J. M., Fayer, M. D. 1993; 73 (2): 850-857
  • The Influence of Local Liquid Structure on Orientational Dynamics: The Isotropic Phase of Liquid Crystals J. Phys. Chem. Stankus, J. J., Torre, R., Fayer, M. D. 1993; 97: 9478-9487
  • FEL-MICROSCOPY FOR THE INVESTIGATION OF TRANSIENT LOCAL HEATING IN SINGLE LIVING CELLS CONF ON FREE-ELECTRON LASER SPECTROSCOPY IN BIOLOGY, MEDICINE, AND MATERIALS SCIENCE Tromberg, B. J., Peterson, K. A., Krasieva, T. B., Shimizu, S., RELLA, C. A., Jeung, A., CHAPMAN, C. F., Dlott, D. D., Fayer, M. D., Schwettman, H. A., Berns, M. W. SPIE - INT SOC OPTICAL ENGINEERING. 1993: 154–161
  • PICOSECOND INFRARED VIBRATIONAL PHOTON-ECHOES AND LIFETIME MEASUREMENTS USING THE STANFORD SUPERCONDUCTING-ACCELERATOR-PUMPED FREE-ELECTRON LASER CONF ON FREE-ELECTRON LASER SPECTROSCOPY IN BIOLOGY, MEDICINE, AND MATERIALS SCIENCE Fayer, M. D., Zimdars, D., Tokmakoff, A., Chen, S., Greenfield, S. R., Smith, T. I., Schwettman, H. A. SPIE - INT SOC OPTICAL ENGINEERING. 1993: 86–93
  • ULTRAFAST DYNAMICS OF NEMATIC LIQUID-CRYSTALS IN THE ISOTROPIC-PHASE CONF ON ULTRAFAST PULSE GENERATION AND SPECTROSCOPY Stankus, J. J., Torre, R., Greenfield, S. R., Sengupta, A., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1993: 263–274
  • INTERFACE SELECTIVE TRANSIENT GRATING SPECTROSCOPY - THEORY AND APPLICATIONS TO THERMAL FLOW AND ACOUSTIC PROPAGATION IN SUPERCONDUCTING THIN-FILMS CONF ON ULTRAFAST PULSE GENERATION AND SPECTROSCOPY Marshall, C. D., Tokmakoff, A., Fishman, I. M., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1993: 302–313
  • SHOCKED ENERGETIC MOLECULAR MATERIALS - CHEMICAL-REACTION INITIATION AND HOT-SPOT FORMATION SYMP ON STRUCTURE AND PROPERTIES OF ENERGETIC MATERIALS, AT THE 1992 FALL MEETING OF THE MATERIALS RESEARCH SOC Fayer, M. D., Tokmakoff, A., Dlott, D. D. MATERIALS RESEARCH SOC. 1993: 379–384
  • Thermal Diffusivity Measurement of Natural and Isotopically Enriched Diamond by Picosecond Infrared Transient Grating Experiments Applied Physics A Tokmakoff, A., Fayer, M. D., Banholtzer, W. 1993; 56: 87-90
  • Optical Parametric Generation of 1 kHz, High Energy, Picosecond Infrared Pulses and Application to Infrared Transient Grating Experiments on Diamond J.O.S.A. B Tokmakoff, A., Marshall, C. D., Fayer, M. D. 1993; 10: 1785-1791
  • Extra Resonances in Time-Domain Four-Wave Mixing Experiments Optics Letters Fourkas, J. T., Trebino, R., Dugan, M. A., Fayer, M. D. 1993; 18: 781-783
  • Shocked Energetic Molecular Materials: Chemical Reaction Initiation and Hot Spot Formation Materials Research Society Fayer, M. D., Tokmakoff, A., Dlott, D. D. edited by Liebenberg, D. H., Armstrong, R. W., Gilman, J. J. 1993: 379–84
  • Dynamics in Complex Liquids: Optical Nonlinear Experiments Femtosecond Spectroscopy of Chemical Reactions Fayer, M. D. 1993: 271-286
  • ELECTRONIC EXCITATION TRANSFER IN CONCENTRATED MICELLE SOLUTIONS JOURNAL OF PHYSICAL CHEMISTRY Marcus, A. H., Diachun, N. A., Fayer, M. D. 1992; 96 (22): 8930-8937
  • ULTRAFAST SIDE GROUP MOTIONS OF POLYMERS JOURNAL OF PHYSICAL CHEMISTRY Sengupta, A., Terazima, M., Fayer, M. D. 1992; 96 (21): 8619-8626
  • SPECTRAL DIFFUSION IN LIQUIDS JOURNAL OF CHEMICAL PHYSICS Stein, A. D., Fayer, M. D. 1992; 97 (5): 2948-2962
  • THE GRATING DECOMPOSITION METHOD - A NEW APPROACH FOR UNDERSTANDING POLARIZATION-SELECTIVE TRANSIENT GRATING EXPERIMENTS .1. THEORY JOURNAL OF CHEMICAL PHYSICS Fourkas, J. T., Trebino, R., Fayer, M. D. 1992; 97 (1): 69-77
  • THE GRATING DECOMPOSITION METHOD - A NEW APPROACH FOR UNDERSTANDING POLARIZATION-SELECTIVE TRANSIENT GRATING EXPERIMENTS .2. APPLICATIONS JOURNAL OF CHEMICAL PHYSICS Fourkas, J. T., Trebino, R., Fayer, M. D. 1992; 97 (1): 78-85
  • NANOSECOND TIME SCALE DYNAMICS OF PSEUDO-NEMATIC DOMAINS IN THE ISOTROPIC-PHASE OF LIQUID-CRYSTALS CHEMICAL PHYSICS LETTERS Stankus, J. J., Torre, R., Marshall, C. D., Greenfield, S. R., Sengupta, A., Tokmakoff, A., Fayer, M. D. 1992; 194 (3): 213-216
  • DYNAMICS IN POLY(DIMETHYLSILOXANE) MELTS - FLUORESCENCE DEPOLARIZATION MEASUREMENTS OF PROBE CHROMOPHORE ORIENTATIONAL RELAXATION JOURNAL OF PHYSICAL CHEMISTRY Stein, A. D., Hoffmann, D. A., Marcus, A. H., Leezenberg, P. B., Frank, C. W., Fayer, M. D. 1992; 96 (13): 5255-5263
  • LOCAL-STRUCTURE DYNAMICS IN LIQUIDS - NONHYDRODYNAMIC ORIENTATIONAL RELAXATION OF 2-ETHYL NAPHTHALENE CHEMICAL PHYSICS LETTERS Greenfield, S. R., Sengupta, A., Stankus, J. J., Fayer, M. D. 1992; 193 (1-3): 49-54
  • THE INFLUENCE OF DIFFUSION ON PHOTOINDUCED ELECTRON-TRANSFER AND GEMINATE RECOMBINATION JOURNAL OF CHEMICAL PHYSICS DORFMAN, R. C., Fayer, M. D. 1992; 96 (10): 7410-7422
  • THERMAL-DIFFUSION, INTERFACIAL THERMAL BARRIER, AND ULTRASONIC PROPAGATION IN YBA2CU3O7-X THIN-FILMS - SURFACE-SELECTIVE TRANSIENT-GRATING EXPERIMENTS PHYSICAL REVIEW B Marshall, C. D., Fishman, I. M., DORFMAN, R. C., Eom, C. B., Fayer, M. D. 1992; 45 (17): 10009-10021
  • THE TRANSIENT GRATING - A HOLOGRAPHIC WINDOW TO DYNAMIC PROCESSES ACCOUNTS OF CHEMICAL RESEARCH Fourkas, J. T., Fayer, M. D. 1992; 25 (5): 227-233
  • DYNAMICS IN A LOW-TEMPERATURE GLASS - FAST GENERATION AND DETECTION OF OPTICAL HOLES JOURNAL OF CHEMICAL PHYSICS Littau, K. A., Dugan, M. A., Chen, S., Fayer, M. D. 1992; 96 (5): 3484-3494
  • REORIENTATIONAL MOTION OF A CROSS-LINK JUNCTION IN A POLY(DIMETHYLSILOXANE) NETWORK MEASURED BY TIME-RESOLVED FLUORESCENCE DEPOLARIZATION JOURNAL OF CHEMICAL PHYSICS Stein, A. D., Hoffman, D. A., Frank, C. W., Fayer, M. D. 1992; 96 (4): 3269-3278
  • Reorientational Motion of a Crosslink Junction in a Poly(dimethylsiloxane) Network Measured by Time-resolved Fluorescence Depolarization J. Chem. Phys. Stein, A. D., Hoffmann, D. A., Frank, C. W., Fayer, M. D. 1992; 96: 3269-3278
  • APPLICATIONS OF INFRARED FREE-ELECTRON LASERS - BASIC RESEARCH ON THE DYNAMICS OF MOLECULAR-SYSTEMS IEEE JOURNAL OF QUANTUM ELECTRONICS Dlott, D. D., Fayer, M. D. 1991; 27 (12): 2697-2713
  • PICOSECOND POLARIZATION-SELECTIVE TRANSIENT GRATING EXPERIMENTS IN SODIUM-SEEDED FLAMES JOURNAL OF CHEMICAL PHYSICS Fourkas, J. T., Brewer, T. R., Kim, H. K., Fayer, M. D. 1991; 95 (8): 5775-5784
  • SURFACE SELECTIVITY IN 4-WAVE-MIXING - TRANSIENT GRATINGS AS A THEORETICAL AND EXPERIMENTAL EXAMPLE JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Fishman, I. M., Marshall, C. D., Meth, J. S., Fayer, M. D. 1991; 8 (9): 1880-1888
  • PICOSECOND PHOTON-ECHO EXPERIMENTS USING A SUPERCONDUCTING ACCELERATOR-PUMPED FREE-ELECTRON LASER JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Bai, Y. S., Greenfield, S. R., Fayer, M. D., Smith, T. I., Frisch, J. C., SWENT, R. L., Schwettman, H. A. 1991; 8 (8): 1652-1662
  • PICOSECOND FEL EXPERIMENTS ON CONDENSED MATTER SYSTEMS 12TH INTERNATIONAL CONF ON FREE ELECTRON LASER ( FEL 90 ) Fayer, M. D. ELSEVIER SCIENCE BV. 1991: 797–97
  • TEMPERATURE-DEPENDENT INTERSYSTEM CROSSING AND TRIPLET TRIPLET ABSORPTION OF RUBRENE IN SOLID-SOLUTION JOURNAL OF LUMINESCENCE Li, S., Fayer, M. D. 1991; 50 (2): 75-81
  • INFLUENCE OF DIFFUSION ON PHOTOINDUCED ELECTRON-TRANSFER JOURNAL OF PHYSICAL CHEMISTRY Song, L., DORFMAN, R. C., Swallen, S. F., Fayer, M. D. 1991; 95 (9): 3454-3457
  • ELECTRONIC EXCITATION TRANSFER IN CLUSTERED CHROMOPHORE SYSTEMS - CALCULATION OF TIME-RESOLVED OBSERVABLES FOR INTERCLUSTER TRANSFER JOURNAL OF CHEMICAL PHYSICS Marcus, A. H., Fayer, M. D. 1991; 94 (8): 5622-5630
  • FORWARD AND BACK PHOTOINDUCED ELECTRON-TRANSFER IN SOLID-SOLUTIONS - A COMPARISON OF THEORETICAL METHODS CHEMICAL PHYSICS LETTERS DORFMAN, R. C., Tachiya, M., Fayer, M. D. 1991; 179 (1-2): 152-158
  • PHOTORESPONSE OF NB FILMS - OBSERVATION OF BIEXPONENTIAL RECOVERY TIMES OF THE SUPERCONDUCTING STATE 1990 APPLIED SUPERCONDUCTIVITY CONF Johnson, M., BLUZER, N., Reyzer, M., Geballe, T. H., Greenfield, S. R., Stankus, J. J., Fayer, M. D., Herring, C. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 1991: 1523–27
  • SUPERCONDUCTING, TRANSITION, AND NORMAL STATE PHOTORESPONSE IN YBCO OBSERVED AT DIFFERENT TEMPERATURES 1990 APPLIED SUPERCONDUCTIVITY CONF BLUZER, N., Fork, D. K., Geballe, T. H., Beasley, M. R., Reizer, M. Y., Greenfield, S. R., Stankus, J. J., Fayer, M. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 1991: 1519–22
  • ANOMALOUS PHOTORESPONSE OF METAL-FILMS APPLIED PHYSICS LETTERS Johnson, M., Beasley, M. R., Geballe, T. H., Greenfield, S. R., Stankus, J. J., Fayer, M. D. 1991; 58 (6): 568-570
  • ULTRASONIC WAVE-PROPAGATION AND BARRIER-LIMITED HEAT-FLOW IN THIN-FILMS OF YBA2CU3O7-X PHYSICAL REVIEW B Marshall, C. D., Fishman, I. M., Fayer, M. D. 1991; 43 (4): 2696-2699
  • PROBING LOW-TEMPERATURE GLASS DYNAMICS BY FAST GENERATION AND DETECTION OF OPTICAL HOLES CHEMICAL PHYSICS LETTERS Littau, K. A., Fayer, M. D. 1991; 176 (6): 551-558
  • PICOSECOND TIME-RESOLVED 4-WAVE-MIXING EXPERIMENTS IN SODIUM-SEEDED FLAMES OPTICS LETTERS Fourkas, J. T., Brewer, T. R., Kim, H. J., Fayer, M. D. 1991; 16 (3): 177-179

    Abstract

    Picosecond four-wave mixing experiments have been used to study collisions in a Na-seeded, premixed, methane-air flame. Population gratings are used to measure Na excited-state quenching collision rates, while polarization gratings are used to measure Na ground-state hyperfine coherence randomizing collision rates and overall Na diffusion rates, even though these processes are slower than the excited-state quenching rate.

    View details for Web of Science ID A1991EV19700021

    View details for PubMedID 19773874

  • OBSERVATION OF FAST TIME SCALE SPECTRAL DIFFUSION IN A LOW-TEMPERATURE GLASS - COMPARISON OF PICOSECOND PHOTON AND STIMULATED ECHOES CHEMICAL PHYSICS LETTERS Narasimhan, L. R., Bai, Y. S., Dugan, M. A., Fayer, M. D. 1991; 176 (3-4): 335-342
  • SOLVENT RELAXATION EFFECTS ON THE KINETICS OF PHOTOINDUCED ELECTRON-TRANSFER REACTIONS JOURNAL OF CHEMICAL PHYSICS Najbar, J., DORFMAN, R. C., Fayer, M. D. 1991; 94 (2): 1081-1092
  • NANOSECOND TIMESCALE OPTICAL INHOMOGENEOUS BROADENING OF DYE MOLECULES IN LIQUIDS AT AND NEAR ROOM-TEMPERATURE CHEMICAL PHYSICS LETTERS Stein, A. D., Fayer, M. D. 1991; 176 (2): 159-166
  • Excitation Transport in Polymeric Solids Laser Optics of Condensed Matter Fayer, M. D. edited by Maradudin, M., Garmine, G., Rebane, R. Plenum Press. 1991: 157–163
  • THERMAL HISTORY AND TEMPERATURE-DEPENDENT PHOTON-ECHO AND HOLE BURNING LINEWIDTHS IN LOW-TEMPERATURE GLYCEROL GLASSES CHEMICAL PHYSICS LETTERS Littau, K. A., Elschner, A., Fayer, M. D. 1990; 175 (3): 149-155
  • PHOTOINDUCED ELECTRON-TRANSFER, GEMINATE RECOMBINATION, AND DIFFUSION IN LIQUID SOLUTION JOURNAL OF PHYSICAL CHEMISTRY DORFMAN, R. C., Lin, Y., Fayer, M. D. 1990; 94 (21): 8007-8009
  • SOLVENT RELAXATION AND ELECTRON BACK TRANSFER FOLLOWING PHOTOINDUCED ELECTRON-TRANSFER IN AN ENSEMBLE OF RANDOMLY DISTRIBUTED DONORS AND ACCEPTORS JOURNAL OF CHEMICAL PHYSICS Lin, Y., DORFMAN, R. C., Fayer, M. D. 1990; 93 (5): 3550-3561
  • NONHYDRODYNAMIC MOLECULAR MOTIONS IN A COMPLEX LIQUID - TEMPERATURE-DEPENDENT DYNAMICS IN PENTYLCYANOBIPHENYL JOURNAL OF CHEMICAL PHYSICS Deeg, F. W., Greenfield, S. R., Stankus, J. J., NEWELL, V. J., Fayer, M. D. 1990; 93 (5): 3503-3514
  • HIGH-TEMPERATURE OPTICAL DEPHASING MECHANISM FOR DYE MOLECULES IN PMMA GLASS CHEMICAL PHYSICS LETTERS Elschner, A., Narasimhan, L. R., Fayer, M. D. 1990; 171 (1-2): 19-24
  • OPTICAL DEPHASING OF A NEAR-INFRARED DYE IN PMMA - PHOTON-ECHOES USING THE SUPERCONDUCTING ACCELERATOR PUMPED FREE-ELECTRON LASER CHEMICAL PHYSICS LETTERS Greenfield, S. R., Bai, Y. S., Fayer, M. D. 1990; 170 (2-3): 133-138
  • HOLE BURNING LINE-SHAPES IN A 2-DIMENSIONAL GLASS - A MODEL FOR HOLE BURNING LINE-SHAPES OF MOLECULES ON SURFACES CHEMICAL PHYSICS LETTERS Pack, D. W., Fayer, M. D. 1990; 168 (3-4): 371-378
  • PROBING ORGANIC GLASSES AT LOW-TEMPERATURE WITH VARIABLE TIME SCALE OPTICAL DEPHASING MEASUREMENTS CHEMICAL REVIEWS Narasimhan, L. R., Littau, K. A., Pack, D. W., Bai, Y. S., Elschner, A., Fayer, M. D. 1990; 90 (3): 439-457
  • DISPERSIVE EXCITATION TRANSPORT AT ELEVATED-TEMPERATURES (50-K-298-K) - EXPERIMENTS AND THEORY JOURNAL OF CHEMICAL PHYSICS Stein, A. D., Peterson, K. A., Fayer, M. D. 1990; 92 (9): 5622-5635
  • DYNAMICS IN THE PRETRANSITIONAL ISOTROPIC-PHASE OF PENTYLCYANOBIPHENYL STUDIED WITH SUBPICOSECOND TRANSIENT GRATING EXPERIMENTS CHEMICAL PHYSICS LETTERS Deeg, F. W., Fayer, M. D. 1990; 167 (6): 527-534
  • SOLVATION SHELL EFFECTS AND SPECTRAL DIFFUSION - PHOTON-ECHO AND OPTICAL HOLE BURNING EXPERIMENTS ON IONIC DYES IN ETHANOL GLASS JOURNAL OF CHEMICAL PHYSICS Pack, D. W., Narasimhan, L. R., Fayer, M. D. 1990; 92 (7): 4125-4138
  • EXPERIMENTAL AND THEORETICAL-ANALYSIS OF TRANSIENT GRATING GENERATION AND DETECTION OF ACOUSTIC WAVE-GUIDE MODES IN ULTRATHIN SOLIDS JOURNAL OF APPLIED PHYSICS Meth, J. S., Marshall, C. D., Fayer, M. D. 1990; 67 (7): 3362-3377
  • 2-LEVEL SYSTEMS AND LOW-TEMPERATURE GLASS DYNAMICS - SPECTRAL DIFFUSION AND THERMAL REVERSIBILITY OF HOLE-BURNING LINEWIDTHS JOURNAL OF CHEMICAL PHYSICS Littau, K. A., Bai, Y. S., Fayer, M. D. 1990; 92 (7): 4145-4158
  • AN EXAMINATION OF RADIATIVE AND NONRADIATIVE EXCITATION TRANSPORT IN THIN ANTHRACENE-CRYSTALS - TRANSIENT GRATING EXPERIMENTS SOLID STATE COMMUNICATIONS Meth, J. S., Marshall, C. D., Fayer, M. D. 1990; 74 (4): 281-284
  • SHOCKED MOLECULAR-SOLIDS - VIBRATIONAL UP PUMPING, DEFECT HOT SPOT FORMATION, AND THE ONSET OF CHEMISTRY JOURNAL OF CHEMICAL PHYSICS Dlott, D. D., Fayer, M. D. 1990; 92 (6): 3798-3812
  • PSEUDOLOCAL MODES OF GUEST MOLECULES IN MIXED MOLECULAR-CRYSTALS - PHOTON-ECHO EXPERIMENTS AND COMPUTER-SIMULATIONS JOURNAL OF CHEMICAL PHYSICS Olson, R. W., Meth, J. S., Marshall, C. D., NEWELL, V. J., Fayer, M. D. 1990; 92 (6): 3323-3334
  • TRANSIENT GRATING OPTICAL KERR EFFECT MEASUREMENTS OF REORIENTATIONAL DYNAMICS IN LIQUIDS AND LIQUID-CRYSTALLINE SAMPLES 19TH EUROPEAN CONGRESS ON MOLECULAR SPECTROSCOPY ( EUCMOS 19 ) Deeg, F. W., Fayer, M. D. ELSEVIER SCIENCE BV. 1990: 19–24
  • QUANTITATIVE MEASUREMENT OF CHAIN CONTRACTION IN A SOLID BLEND OF 2 INCOMPATIBLE POLYMERS - POLY(METHYL METHACRYLATE) POLY(VINYL ACETATE) MACROMOLECULES Peterson, K. A., Stein, A. D., Fayer, M. D. 1990; 23 (1): 111-120
  • Dispersive Excitation Transport at Elevated Temperatures (50-298 K): Experiments and Theory J. Chem. Phys. Stein, A. D., Peterson, K. A., Fayer, M. D. 1990; 92: 5622-5635
  • LOW-TEMPERATURE GLASS DYNAMICS PROBED BY OPTICAL DEPHASING MEASUREMENTS JOURNAL OF LUMINESCENCE Narasimhan, L. R., Littau, K. A., Bai, Y. S., Pack, D. W., Elschner, A., Fayer, M. D. 1990; 45 (1-6): 49-53
  • ROTATIONAL-DYNAMICS IN SIMPLE AND NEMATOGENIC LIQUIDS - TRANSIENT GRATING OPTICAL KERR EFFECT INVESTIGATIONS 7TH INTERNATIONAL CONF ON ULTRAFAST PHENOMENA Deeg, F. W., Fayer, M. D. SPRINGER-VERLAG BERLIN. 1990: 447–449
  • MULTITIMESCALE DYNAMICS IN GLASSES - OPTICAL DEPHASING AND SOLUTE-SOLVENT INTERACTIONS CONF ON PICOSECOND AND FEMTOSECOND SPECTROSCOPY FROM LABORATORY TO REAL WORLD Narasimhan, L. R., Pack, D. W., Elschner, A., Bai, Y. S., Fayer, M. D. SPIE - INT SOC OPTICAL ENGINEERING. 1990: 43–52
  • Photoinduced Electron Transfer, Geminate Recombination, and Diffusion in Liquid Solutions J. Phys. Chem. Dorfman, R. C., Lin, Y., Fayer, M. D. 1990; 94: 8007-8009
  • THE NATURE OF GLASS DYNAMICS - THERMAL REVERSIBILITY OF SPECTRAL DIFFUSION IN A LOW-TEMPERATURE GLASS CHEMICAL PHYSICS LETTERS Bai, Y. S., Littau, K. A., Fayer, M. D. 1989; 162 (6): 449-454
  • GENERATION AND DETECTION OF ACOUSTIC WAVE-GUIDE MODES IN ULTRATHIN CRYSTALS USING THE TRANSIENT GRATING TECHNIQUE CHEMICAL PHYSICS LETTERS Meth, J. S., Marshall, C. D., Fayer, M. D. 1989; 162 (4-5): 306-312
  • PICOSECOND TIME-SCALE PHASE-RELATED OPTICAL PULSES - MEASUREMENT OF SODIUM OPTICAL COHERENCE DECAY BY OBSERVATION OF INCOHERENT FLUORESCENCE JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Fourkas, J. T., Wilson, W. L., Wackerle, G., Frost, A. E., Fayer, M. D. 1989; 6 (10): 1905-1910
  • DISPERSIVE ELECTRONIC EXCITATION TRANSPORT IN POLYMERIC SOLIDS AT AND NEAR ROOM-TEMPERATURE CHEMICAL PHYSICS LETTERS Stein, A. D., Peterson, K. A., Fayer, M. D. 1989; 161 (1): 16-22
  • EXPERIMENTAL INVESTIGATION OF DONOR-ACCEPTOR ELECTRON-TRANSFER AND BACK TRANSFER IN SOLID-SOLUTIONS JOURNAL OF PHYSICAL CHEMISTRY DORFMAN, R. C., Lin, Y., Fayer, M. D. 1989; 93 (17): 6388-6396
  • ANALYSIS OF COMPLEX MOLECULAR-DYNAMICS IN AN ORGANIC LIQUID BY POLARIZATION SELECTIVE SUBPICOSECOND TRANSIENT GRATING EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Deeg, F. W., Fayer, M. D. 1989; 91 (4): 2269-2279
  • TIME EVOLUTION OF NON-PHOTOCHEMICAL HOLE BURNING LINEWIDTHS - OBSERVATION OF SPECTRAL DIFFUSION AT LONG TIMES CHEMICAL PHYSICS LETTERS Littau, K. A., Bai, Y. S., Fayer, M. D. 1989; 159 (1): 1-6
  • ANISOTROPIC REORIENTATIONAL RELAXATION OF BIPHENYL - TRANSIENT GRATING OPTICAL KERR EFFECT MEASUREMENTS JOURNAL OF CHEMICAL PHYSICS Deeg, F. W., Stankus, J. J., Greenfield, S. R., NEWELL, V. J., Fayer, M. D. 1989; 90 (12): 6893-6902
  • TIME SCALES AND OPTICAL DEPHASING MEASUREMENTS - INVESTIGATION OF DYNAMICS IN COMPLEX-SYSTEMS PHYSICAL REVIEW B Bai, Y. S., Fayer, M. D. 1989; 39 (15): 11066-11084
  • APPLICATION OF A 2-COLOR FREE-ELECTRON LASER TO CONDENSED-MATTER MOLECULAR-DYNAMICS JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Dlott, D. D., Fayer, M. D. 1989; 6 (5): 977-994
  • TUNABLE SUBPICOSECOND DYE-LASER AMPLIFIED AT 1 KHZ BY A CAVITY-DUMPED, Q-SWITCHED, AND MODE-LOCKED ND-YAG LASER JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS NEWELL, V. J., Deeg, F. W., Greenfield, S. R., Fayer, M. D. 1989; 6 (2): 257-263
  • FLUORESCENCE DEPOLARIZATION OF CHROMOPHORES IN POLYMERIC SOLIDS MACROMOLECULES Peterson, K. A., Zimmt, M. B., Fayer, M. D., Jeng, Y. H., Frank, C. W. 1989; 22 (2): 874-879
  • Electronic Excitation Transport in Restricted Geometries Molecular Dynamics in Restricted Geometries Peterson, K. A., Stein, A., Fayer, M. D. edited by Klafter, J., Drake, J. M. John Wiley & Sons, New York. 1989: 39–75
  • A New Approach to the Nonlinear Spectroscopic Investigation of Dynamics in Complex Solids: Theory and Experiments Comments on Condensed Matter Physics Bai, Y. S., Fayer, M. D. 1989; 14: 243-364
  • TIME-DEPENDENCE OF DONOR-ACCEPTOR ELECTRON-TRANSFER AND BACK TRANSFER IN SOLID-SOLUTION JOURNAL OF CHEMICAL PHYSICS Lin, Y., DORFMAN, R. C., Fayer, M. D. 1989; 90 (1): 159-170
  • Polymers in Solids: Structure and Interactions Measured by Electronic Excitation Transport Optical Techniques to Characterizing Polymer Systems Peterson, K. A., Stein, A. D., Fayer, M. D., Bässler, H. Elsevier Science Publishers, B.V., The Netherlands. 1989: 277–324
  • OPTICAL DEPHASING IN GLASSES - THEORETICAL COMPARISON OF THE INCOHERENT PHOTON-ECHO, ACCUMULATED GRATING ECHO, AND 2-PULSE PHOTON-ECHO EXPERIMENTS CHEMICAL PHYSICS Bai, Y. S., Fayer, M. D. 1988; 128 (1): 135-155
  • SOLUTE SOLVENT DYNAMICS AND INTERACTIONS IN GLASSY MEDIA - PHOTON-ECHO AND OPTICAL HOLE BURNING STUDIES OF CRESYL VIOLET IN ETHANOL GLASS CHEMICAL PHYSICS LETTERS Narasimhan, L. R., Pack, D. W., Fayer, M. D. 1988; 152 (4-5): 287-293
  • PHOTOINDUCED ELECTRON-TRANSFER AND BACK TRANSFER IN SYSTEMS OF RANDOMLY DISTRIBUTED DONORS AND ACCEPTORS - PICOSECOND TRANSIENT GRATING EXPERIMENTS JOURNAL OF PHYSICAL CHEMISTRY DORFMAN, R. C., Lin, Y., Zimmt, M. B., Baumann, J., DOMINGUE, R. P., Fayer, M. D. 1988; 92 (15): 4258-4260
  • EFFECTS OF SPECTRAL DIFFUSION IN INCOHERENT PHOTON-ECHO EXPERIMENTS PHYSICAL REVIEW B Bai, Y. S., Fayer, M. D. 1988; 37 (17): 10440-10443
  • POLARITON EFFECTS IN TRANSIENT GRATING EXPERIMENTS PERFORMED ON ANTHRACENE SINGLE-CRYSTALS CHEMICAL PHYSICS LETTERS Rose, T. S., NEWELL, V. J., Meth, J. S., Fayer, M. D. 1988; 145 (5): 475-480
  • SHORT POLYMER-CHAIN STATISTICS AND THE RELATIONSHIP TO END TO END ELECTRONIC EXCITATION TRANSPORT - RANDOM-WALKS WITH VARIABLE STEP LENGTHS MACROMOLECULES Zimmt, M. B., Peterson, K. A., Fayer, M. D. 1988; 21 (4): 1145-1154
  • THEORY OF THE PHONON PERTURBED PHOTON-ECHO EXPERIMENT - DIRECT DETERMINATION OF ELECTRONIC EXCITATION PHONON COUPLING JOURNAL OF CHEMICAL PHYSICS Wilson, W. L., Wackerle, G., Fayer, M. D. 1988; 88 (6): 3407-3416
  • DYNAMICS IN LOW-TEMPERATURE GLASSES - THEORY AND EXPERIMENTS ON OPTICAL DEPHASING, SPECTRAL DIFFUSION, AND HYDROGEN TUNNELING JOURNAL OF CHEMICAL PHYSICS Berg, M., Walsh, C. A., Narasimhan, L. R., Littau, K. A., Fayer, M. D. 1988; 88 (3): 1564-1587
  • An Investigation of the Mechanism of Nonphotochemical Hole Burning of Resorufin in Ethanol Glass Chem. Phys. Lett. Kokai, F., Tanaka, H., Brauman, J. L., Fayer, M. D. 1988; 143: 1-5
  • AN INVESTIGATION OF THE MECHANISM OF NON-PHOTOCHEMICAL HOLE BURNING OF RESORUFIN IN ETHANOL GLASS CHEMICAL PHYSICS LETTERS Kokai, F., Tanaka, H., Brauman, J. I., Fayer, M. D. 1988; 143 (1): 1-5
  • Picosecond Transient Grating Experiments on Hydrogenated Amorphous Silicon International Conference on Unconventional Photoactive Solids Newell, V. J., Feyer, M. D. 1988: 225–236
  • EFFECT OF HYDROGEN-BOND STRENGTH ON RESORUFIN NONPHOTOCHEMICAL HOLE BURNING IN ETHANOL-2,2,2-TRIFLUOROETHANOL GLASSES CHEMICAL PHYSICS LETTERS Tanaka, H., Kokai, F., Brauman, J. I., Fayer, M. D. 1987; 142 (5): 371-375
  • PICOSECOND PHOTON-ECHO AND OPTICAL HOLE BURNING STUDIES OF CHROMOPHORES IN ORGANIC GLASSES JOURNAL OF LUMINESCENCE Berg, M., Walsh, C. A., Narasimhan, L. R., Fayer, M. D. 1987; 38 (1-6): 9-14
  • OPTICAL HOMOGENEOUS LINEWIDTHS OF RESORUFIN IN ETHANOL GLASS - AN APPARENT CONTRADICTION BETWEEN HOLE-BURNING AND PHOTON-ECHO RESULTS - COMMENT CHEMICAL PHYSICS LETTERS Walsh, C. A., Berg, M., Narasimhan, L. R., Fayer, M. D. 1987; 139 (5): 485-490
  • IMPURITY PERTURBED DOMAINS - RESONANT ENHANCEMENT OF BULK MODE CARS BY COUPLING TO THE ELECTRONIC STATES OF DILUTE IMPURITIES JOURNAL OF CHEMICAL PHYSICS Wilson, W. L., Wackerle, G., Fayer, M. D. 1987; 87 (5): 2498-2504
  • HOMOGENEOUS OPTICAL DEPHASING AND LINE BROADENING PROCESSES IN AN ORGANIC GLASS - COMPARISON OF THE TEMPERATURE DEPENDENCES OF PICOSECOND PHOTON-ECHO AND HOLE BURNING EXPERIMENTS CHEMICAL PHYSICS LETTERS Berg, M., Walsh, C. A., Narasimhan, L. R., Littau, K. A., Fayer, M. D. 1987; 139 (1): 66-71
  • GAS-PHASE DYNAMICS AND SPECTROSCOPY PROBED WITH PICOSECOND TRANSIENT GRATING EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Rose, T. S., Wilson, W. L., Wackerle, G., Fayer, M. D. 1987; 86 (10): 5370-5391
  • PICOSECOND TRANSIENT GRATING EXPERIMENTS IN SODIUM VAPOR - VELOCITY AND POLARIZATION EFFECTS JOURNAL OF PHYSICAL CHEMISTRY Rose, T. S., Wilson, W. L., Wackerle, G., Fayer, M. D. 1987; 91 (7): 1704-1707
  • PROBING INTERMOLECULAR INTERACTIONS WITH PICOSECOND PHOTON-ECHO EXPERIMENTS ACCOUNTS OF CHEMICAL RESEARCH Walsh, C. A., Berg, M., Narasimhan, L. R., Fayer, M. D. 1987; 20 (3): 120-126
  • ULTRAFAST OPTICAL DEPHASING IN A LOW-TEMPERATURE ORGANIC GLASS CHEMICAL PHYSICS LETTERS Walsh, C. A., Berg, M., Narasimhan, L. R., Littau, K. A., Fayer, M. D. 1987; 134 (3): 268-272
  • QUANTITATIVE-DETERMINATION OF THE RADIUS OF GYRATION OF POLY(METHYL METHACRYLATE) IN THE AMORPHOUS SOLID-STATE BY TIME-RESOLVED FLUORESCENCE DEPOLARIZATION MEASUREMENTS OF EXCITATION TRANSPORT MACROMOLECULES Peterson, K. A., Zimmt, M. B., Linse, S., DOMINGUE, R. P., Fayer, M. D. 1987; 20 (1): 168-175
  • ENSEMBLE AVERAGE CONFORMATION OF ISOLATED POLYMER COILS IN SOLID BLENDS USING ELECTRONIC EXCITATION TRANSPORT ACS SYMPOSIUM SERIES Peterson, K. A., Zimmt, M. B., Linse, S., Fayer, M. D. 1987; 358: 323-342
  • A PICOSECOND PHOTON-ECHO STUDY OF A CHROMOPHORE IN AN ORGANIC GLASS - TEMPERATURE-DEPENDENCE AND COMPARISON TO NONPHOTOCHEMICAL HOLE BURNING JOURNAL OF CHEMICAL PHYSICS Walsh, C. A., Berg, M., Narasimhan, L. R., Fayer, M. D. 1987; 86 (1): 77-87
  • ELECTRONIC EXCITATION TRANSPORT ON ISOLATED, FLEXIBLE POLYMER-CHAINS IN THE AMORPHOUS SOLID-STATE RANDOMLY TAGGED OR END TAGGED WITH CHROMOPHORES JOURNAL OF CHEMICAL PHYSICS Peterson, K. A., Fayer, M. D. 1986; 85 (8): 4702-4711
  • INFLUENCE OF ORIENTATIONAL FLUCTUATIONS ON ELECTRON-TRANSFER IN SYSTEMS OF DONOR-ACCEPTOR PAIRS JOURNAL OF PHYSICAL CHEMISTRY DOMINGUE, R. P., Fayer, M. D. 1986; 90 (21): 5141-5146
  • EXCITATION TRANSFER IN DISORDERED TWO-DIMENSIONAL AND ANISOTROPIC 3-DIMENSIONAL SYSTEMS - EFFECTS OF SPATIAL GEOMETRY ON TIME-RESOLVED OBSERVABLES JOURNAL OF CHEMICAL PHYSICS Baumann, J., Fayer, M. D. 1986; 85 (7): 4087-4107
  • OPTICAL DEPHASING OF CHROMOPHORES IN AN ORGANIC GLASS - PICOSECOND PHOTON-ECHO AND HOLE BURNING EXPERIMENTS CHEMICAL PHYSICS LETTERS Walsh, C. A., Berg, M., Narasimhan, L. R., Fayer, M. D. 1986; 130 (1-2): 6-11
  • EFFECT OF CHOLESTEROL ON VISCOELASTIC PROPERTIES OF DIPALMITOYLPHOSPHATIDYLCHOLINE MULTIBILAYERS AS MEASURED BY A LASER-INDUCED ULTRASONIC PROBE BIOCHEMISTRY ELSAYED, M. Y., GUION, T. A., Fayer, M. D. 1986; 25 (17): 4825-4832

    Abstract

    Using a novel laser-induced ultrasonic probe, we have examined the bulk viscoelastic properties of fully hydrated dipalmitoylphosphatidylcholine (DPPC) aligned multibilayers in terms of the anisotropic in-plane elastic stiffness (C11) and viscosity (eta 11). Our measurements of C11 are in accord with those reported on Brillouin light scattering on a similar system. Our measurements on viscosity are the first of their kind and are, on the average, a factor of 10 lower than microviscosities estimated by spectroscopic techniques. We report the first comprehensive study of the effects of cholesterol on the bulk mechanical properties of DPPC multibilayers. At temperatures above the phase transition temperature of DPPC (Tc), an increase in both C11 and eta 11 is noticed when cholesterol is incorporated in the multibilayers. However, at temperatures below Tc, no measurable changes are detected in either C11 or eta 11. These results, reflecting changes in the bulk viscoelastic properties of the multibilayers, differ from the changes reported by local fluidity parameters in that the latter indicate a decrease in the bilayer fluidity in the presence of cholesterol above Tc and an increase below Tc ("dual effect" of cholesterol). Our data suggest that the "dual effect" of cholesterol is noticeable only on a molecular scale. Increasing cholesterol concentrations higher than 20 mol % cease to further affect C11 or eta 11 of the DPPC multibilayers. This agrees with various results reported in the literature, by techniques measuring the local effects of cholesterol, and supports the changes in molecular organization postulated to occur when cholesterol concentration reaches 20 mol % in the lipid bilayers.

    View details for Web of Science ID A1986D754500016

    View details for PubMedID 3768316

  • PICOSECOND HOLOGRAPHIC GRATING GENERATION OF ULTRASONIC-WAVES IEEE JOURNAL OF QUANTUM ELECTRONICS Fayer, M. D. 1986; 22 (8): 1437-1452
  • OPTICAL DEPHASING OF THE ELECTRONIC-TRANSITIONS OF DELOCALIZED MOLECULAR DIMER STATES JOURNAL OF CHEMICAL PHYSICS Lee, H. W., Fayer, M. D. 1986; 84 (10): 5463-5478
  • DELOCALIZATION OF ELECTRONIC EXCITATIONS IN DISORDERED MOLECULAR-SYSTEMS CHEMICAL PHYSICS LETTERS Gulotty, R. J., Walsh, C. A., Patterson, F. G., Wilson, W. L., Fayer, M. D. 1986; 125 (5-6): 507-513
  • PROBING GAS-PHASE DYNAMICS WITH PICOSECOND TRANSIENT GRATING SPECTROSCOPY CHEMICAL PHYSICS LETTERS Rose, T. S., Fayer, M. D. 1985; 117 (1): 12-17
  • A LASER-INDUCED ULTRASONIC PROBE OF THE MECHANICAL-PROPERTIES OF ALIGNED LIPID MULTIBILAYERS BIOPHYSICAL JOURNAL EYRING, G., Fayer, M. D. 1985; 47 (1): 37-42

    Abstract

    The recently developed laser-induced phonon spectroscopy (LIPS) technique is applied to the determination of dynamic mechanical properties of aligned dilauroylphosphatidylcholine (DLPC) multibilayer arrays containing 2 and 20% water by weight. Sample excitation by two crossed 100-ps laser pulses generates a longitudinal ultrasonic wave whose wavelength depends on the crossing angle. In these experiments, the acoustic wave propagates parallel to the bilayer planes. The ultrasonic velocity and attenuation are monitored through the diffraction of a variably delayed probe pulse by the acoustic grating. The velocity measures the lateral area compressibility of the bilayers, while the attenuation is related to the viscosity. Velocities obtained in the gel and liquid crystal phases are compared with those found previously using Brillouin scattering. The acoustic attenuation is shown to be an order of magnitude more sensitive to the gel-liquid crystal phase transition than the velocity. The lipid area compressibility and viscosity of DLPC-20% water multilayers with and without 100 mM CaCl2 are found to be identical within our experimental error.

    View details for Web of Science ID A1985TZ82100005

    View details for PubMedID 3978188

  • SURFACE QUENCHING OF OPTICALLY GENERATED CARRIERS IN THIN-FILM HYDROGENATED AMORPHOUS-SILICON - PICOSECOND TRANSIENT-GRATING EXPERIMENTS PHYSICAL REVIEW B NEWELL, V. J., Rose, T. S., Fayer, M. D. 1985; 32 (12): 8035-8040
  • TRANSIENT PROPERTIES OF TRIPLET BOTTLENECK HOLEBURNING IN AN OPTICALLY THICK SAMPLE CHEMICAL PHYSICS Deeg, F. W., Madison, L., Fayer, M. D. 1985; 94 (1-2): 265-271
  • Electronic Excitation Transport in Disordered Infinite Volume Systems Int. Rev. Phys. Chem. Ediger, M. D., Fayer, M. D. 1985; 4: 207-235
  • DETERMINATION OF THE GUEST RADIUS OF GYRATION IN POLYMER BLENDS - TIME-RESOLVED MEASUREMENTS OF EXCITATION TRANSPORT INDUCED FLUORESCENCE DEPOLARIZATION MACROMOLECULES Ediger, M. D., DOMINGUE, R. P., Peterson, K. A., Fayer, M. D. 1985; 18 (6): 1182-1190
  • INHOMOGENEOUS BROADENING OF ELECTRONIC-TRANSITIONS OF CHROMOPHORES IN CRYSTALS AND GLASSES - ANALYSIS OF HOLE BURNING AND FLUORESCENCE LINE NARROWING EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Lee, H. W., Walsh, C. A., Fayer, M. D. 1985; 82 (9): 3948-3958
  • NONPHOTOCHEMICAL HOLE BURNING AND INTERSYSTEM CROSSING IN THE PENTACENE BENZOIC-ACID SYSTEM - DEUTERIUM EFFECTS JOURNAL OF LUMINESCENCE Walsh, C. A., Fayer, M. D. 1985; 34 (1-2): 37-45
  • ELECTRON-TRANSFER BETWEEN MOLECULES RANDOMLY DISTRIBUTED IN A GLASS JOURNAL OF CHEMICAL PHYSICS DOMINGUE, R. P., Fayer, M. D. 1985; 83 (5): 2242-2251
  • EXCITATION TRANSPORT AND DYNAMICS IN SOLID-STATE SYSTEMS JOURNAL OF LUMINESCENCE Fayer, M. D. 1984; 31-2 (DEC): 525-529
  • EXCITATION TRANSPORT AND TRAPPING IN A SYNTHETIC CHLOROPHYLLIDE SUBSTITUTED HEMOGLOBIN - ORIENTATION OF THE CHLOROPHYLL-S1 TRANSITION DIPOLE BIOCHEMISTRY Moog, R. S., Kuki, A., Fayer, M. D., Boxer, S. G. 1984; 23 (7): 1564-1571

    Abstract

    Excitation transport in synthetic zinc chlorophyllide substituted hemoglobin has been observed by pico -second time-resolved fluorescence depolarization experiments. In this hybrid molecular system, two zinc chlorophyllide molecules are substituted into the beta-chains of hemoglobin, while deoxy hemes remain in the alpha-chains. The rate of excitation transfer between the two chlorophyllides is analyzed in terms of the distance and orientation dependences predicted by the F orster dipole-dipole theory. In this analysis, the beta-beta interchromophore geometry is assumed to be that of the deoxyhemoglobin crystal structure. When combined with steady-state fluorescence depolarization data of the complementary hybrid containing zinc chlorophyllide in the alpha-chains, these experiments provide the necessary information to determine the orientation of the S1 transition dipole moment in the zinc chlorophyllide molecule. We also find that the fluorescence lifetime of the zinc chlorophyllide is 1.42 ns when the heme is in the deoxy state but 3.75 ns when the heme is ligated to carbon monoxide. This is explained by irreversible excitation transfer from the S1 state of the zinc chlorophyllide to the lower energy excited states present in deoxy heme.

    View details for Web of Science ID A1984SK48400034

    View details for PubMedID 6722108

  • HOPPING TRANSPORT ON A RANDOMLY SUBSTITUTED LATTICE FOR LONG-RANGE AND NEAREST NEIGHBOR INTERACTIONS JOURNAL OF CHEMICAL PHYSICS Loring, R. F., ANDERSEN, H. C., Fayer, M. D. 1984; 80 (11): 5731-5744
  • THEORY OF PHOTON-ECHOES FROM INTERACTING IMPURITIES IN CRYSTALS WITH INHOMOGENEOUSLY BROADENED ABSORPTION-SPECTRA JOURNAL OF CHEMICAL PHYSICS Loring, R. F., Anderson, H. C., Fayer, M. D. 1984; 81 (12): 5395-5404
  • A PICOSECOND HOLOGRAPHIC GRATING APPROACH TO MOLECULAR-DYNAMICS IN ORIENTED LIQUID-CRYSTAL FILMS JOURNAL OF CHEMICAL PHYSICS EYRING, G., Fayer, M. D. 1984; 81 (10): 4314-4321
  • OPTICAL DEPHASING OF MOLECULAR DIMERS IN MIXED-CRYSTALS - PICOSECOND PHOTON-ECHO EXPERIMENTS CHEMICAL PHYSICS LETTERS Patterson, F. G., Wilson, W. L., Lee, H. W., Fayer, M. D. 1984; 110 (1): 7-13
  • PICOSECOND TRANSIENT GRATING MEASUREMENTS OF SINGLET EXCITON TRANSPORT IN ANTHRACENE SINGLE-CRYSTALS CHEMICAL PHYSICS LETTERS Rose, T. S., Righini, R., Fayer, M. D. 1984; 106 (1-2): 13-19
  • A COHERENT PHOTOACOUSTIC APPROACH TO EXCITED-STATE-EXCITED-STATE ABSORPTION-SPECTROSCOPY - APPLICATION TO THE INVESTIGATION OF A NEAR-RESONANT CONTRIBUTION TO ULTRASONIC DIFFRACTION JOURNAL OF PHYSICAL CHEMISTRY Miller, R. J., Pierre, M., Rose, T. S., Fayer, M. D. 1984; 88 (14): 3021-3025
  • HOPPING TRANSPORT ON A RANDOMLY SUBSTITUTED LATTICE IN THE PRESENCE OF DILUTE DEEP TRAPS CHEMICAL PHYSICS Loring, R. F., ANDERSEN, H. C., Fayer, M. D. 1984; 85 (1): 149-164
  • LASER-INDUCED PHENOMENA AT LIQUID-GLASS INTERFACES - PARTICLE DEPOSITION AND HOLOGRAPHIC BUBBLE GRATING FORMATION JOURNAL OF APPLIED PHYSICS EYRING, G., Fayer, M. D. 1984; 55 (11): 4072-4080
  • ELECTRONIC EXCITATION TRANSPORT IN DISORDERED FINITE VOLUME SYSTEMS JOURNAL OF PHYSICAL CHEMISTRY Ediger, M. D., Fayer, M. D. 1984; 88 (25): 6108-6116
  • INTERSYSTEM CROSSING FROM SINGLET-STATES OF MOLECULAR DIMERS AND MONOMERS IN MIXED MOLECULAR-CRYSTALS - PICOSECOND STIMULATED PHOTON-ECHO EXPERIMENTS CHEMICAL PHYSICS Patterson, F. G., Lee, H. W., Wilson, W. L., Fayer, M. D. 1984; 84 (1): 51-60
  • PICOSECOND STUDIES OF EXCITATION TRANSPORT IN A FINITE VOLUME - THE CLUSTERED TRANSPORT-SYSTEM OCTADECYL RHODAMINE-B IN TRITON X-100 MICELLES JOURNAL OF CHEMICAL PHYSICS Ediger, M. D., DOMINGUE, R. P., Fayer, M. D. 1984; 80 (3): 1246-1253
  • EXCITATION TRANSPORT ON SUBSTITUTIONALLY DISORDERED LATTICES PHYSICAL REVIEW LETTERS Loring, R. F., ANDERSEN, H. C., Fayer, M. D. 1983; 50 (17): 1324-1327
  • Exciton Coherence Spectroscopy and Excitation Dynamics of Condensed Molecular Systems Fayer, M. D. edited by Agranovich, V. M., Hochstrasser, M. R. North Holland. 1983: 185–248
  • EXCITATION TRANSPORT ON SUBSTITUTIONALLY DISORDERED LATTICES Loring, R. F., ANDERSEN, H. C., Fayer, M. D. AMER INST PHYSICS. 1983: 1389–89
  • NEW APPROACH TO PROBING POLYMER AND POLYMER BLEND STRUCTURE USING ELECTRONIC EXCITATION TRANSPORT MACROMOLECULES Ediger, M. D., Fayer, M. D. 1983; 16 (12): 1839-1844
  • ELECTRONIC EXCITED-STATE TRANSPORT AMONG MOLECULES DISTRIBUTED RANDOMLY IN A FINITE VOLUME JOURNAL OF CHEMICAL PHYSICS Ediger, M. D., Fayer, M. D. 1983; 78 (5): 2518-2524
  • ELECTRONIC EXCITED-STATE TRANSPORT AND TRAPPING IN DISORDERED-SYSTEMS - PICOSECOND FLUORESCENCE MIXING, TRANSIENT GRATING, AND PROBE PULSE EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Miller, R. J., Pierre, M., Fayer, M. D. 1983; 78 (8): 5138-5146
  • HOLOGRAPHIC GENERATION OF BUBBLE GRATINGS AT LIQUID-GLASS INTERFACES AND THE DYNAMICS OF BUBBLES ON SURFACES CHEMICAL PHYSICS LETTERS EYRING, G., Fayer, M. D. 1983; 98 (5): 428-432
  • DYNAMICS OF MOLECULES IN CONDENSED PHASES - PICOSECOND HOLOGRAPHIC GRATING EXPERIMENTS ANNUAL REVIEW OF PHYSICAL CHEMISTRY Fayer, M. D. 1982; 33: 63-87
  • VISCOSITY DEPENDENCE OF THE ROTATIONAL REORIENTATION OF RHODAMINE-B IN MONO-ALCOHOL AND POLY-ALCOHOL - PICOSECOND TRANSIENT GRATING EXPERIMENTS JOURNAL OF PHYSICAL CHEMISTRY Moog, R. S., Ediger, M. D., Boxer, S. G., Fayer, M. D. 1982; 86 (24): 4694-4700
  • Nonphotochemical Hole Burning and Antihole Production in the Mixed Molecular Crystal Pentacene in Benzoic Acid J. Chem. Phys. Olson, R. W., Patterson, F. G., Lee, H. W., Fayer, M. D., Shelby, R. M., Burum, D. P., MacFarlane, R. M. 1982; 77: 2283-2289
  • Picosecond Holographic Grating Experiments on Molecular Condensed Phases Picosecond Phenomena III. Fayer, M. D. 1982: 82-86
  • LASER-INDUCED ULTRASONICS - A DYNAMIC HOLOGRAPHIC APPROACH TO THE MEASUREMENT OF WEAK ABSORPTIONS, OPTOELASTIC CONSTANTS AND ACOUSTIC ATTENUATION CHEMICAL PHYSICS Miller, R. J., Casalegno, R., Nelson, K. A., Fayer, M. D. 1982; 72 (3): 371-379
  • Viscosity Dependence of the Rotational Reorientation of Rhodamine B in Mono- and Polyalcohol. Picosecond Transient Grating Experiments J. Phys. Chem Moog, R. S., Ediger, M. D., Boxer, S. G., Fayer, M. D. 1982; 86: 4694-4700
  • ON THE REFRACTIVE-INDEX CORRECTION IN LUMINESCENCE SPECTROSCOPY - COMMENT CHEMICAL PHYSICS LETTERS Ediger, M. D., Moog, R. S., Boxer, S. G., Fayer, M. D. 1982; 88 (1): 123-127
  • Electronic Excited State Transport and Trapping in One and Two Dimensional Disordered Systems Chem. Phys. Loring, R. F., Fayer, M. D. 1982; 70: 139-147
  • OPTICAL-GENERATION OF TUNABLE ULTRASONIC-WAVES JOURNAL OF APPLIED PHYSICS Nelson, K. A., Miller, R. J., LUTZ, D. R., Fayer, M. D. 1982; 53 (2): 1144-1149
  • ELECTRONIC EXCITED-STATE TRANSPORT AND TRAPPING IN ONE-DIMENSIONAL AND TWO-DIMENSIONAL DISORDERED-SYSTEMS CHEMICAL PHYSICS Loring, R. F., Fayer, M. D. 1982; 70 (1-2): 139-147
  • TEMPERATURE-DEPENDENT DEPHASING OF DELOCALIZED DIMER STATES OF PENTACENE IN PARA-TERPHENYL - PICOSECOND PHOTON-ECHO EXPERIMENTS CHEMICAL PHYSICS LETTERS Lee, H. W., Patterson, F. G., Olson, R. W., Wiersma, D. A., Fayer, M. D. 1982; 90 (3): 172-177
  • LASER-INDUCED EXCITED-STATE AND ULTRASONIC WAVE GRATINGS - AMPLITUDE AND PHASE GRATING CONTRIBUTIONS TO DIFFRACTION JOURNAL OF CHEMICAL PHYSICS Nelson, K. A., Casalegno, R., Miller, R. J., Fayer, M. D. 1982; 77 (3): 1144-1152
  • ELECTRONIC EXCITED-STATE TRANSPORT AND TRAPPING IN SOLUTION JOURNAL OF CHEMICAL PHYSICS Loring, R. F., ANDERSEN, H. C., Fayer, M. D. 1982; 76 (4): 2015-2027
  • NON-PHOTOCHEMICAL HOLE BURNING AND ANTI-HOLE PRODUCTION IN THE MIXED MOLECULAR-CRYSTAL PENTACENE IN BENZOIC-ACID JOURNAL OF CHEMICAL PHYSICS Olson, R. W., Lee, H. W., Patterson, F. G., Fayer, M. D., Shelby, R. M., BURUM, D. P., Macfarlane, R. M. 1982; 77 (5): 2283-2289
  • PICOSECOND TRANSIENT GRATING GENERATION OF TUNABLE ULTRASONIC-WAVES PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS Nelson, K. A., Miller, R. J., LUTZ, D. R., Fayer, M. D. 1982; 322: 68-74
  • OPTICAL-DENSITY EFFECTS IN PHOTON-ECHO EXPERIMENTS JOURNAL OF CHEMICAL PHYSICS Olson, R. W., Lee, H. W., Patterson, F. G., Fayer, M. D. 1982; 76 (1): 31-39
  • CORRELATION-FUNCTION ANALYSIS OF COHERENT OPTICAL TRANSIENTS AND FLUORESCENCE FROM A QUASI-2-LEVEL SYSTEM PHYSICAL REVIEW A Skinner, J. L., ANDERSEN, H. C., Fayer, M. D. 1981; 24 (4): 1994-2008
  • LUMINESCENT SOLAR CONCENTRATORS AND THE REABSORPTION PROBLEM APPLIED OPTICS Olson, R. W., Loring, R. F., Fayer, M. D. 1981; 20 (17): 2934-2940

    Abstract

    The problem of reabsorption in luminescent solar concentrators (LSC) is discussed. A mathematical development is presented which enables the LSC gain to be calculated based on the optical properties of the materials and a random walk formalism. Two- and three-dimensional analyses are used. A detailed set of calculations for a common dye (rhodamine 6G) is used to examine the practicality of employing a single dye. The effects of diameter, thickness, and quantum yield on the LSC output are presented. The spectrum of the LSC output as a function of concentration is calculated. It is suggested that LSCs can be made more efficient with a system which utilizes radiationless electronic excited state transport and trapping as intermediate steps between absorption and reemission. Trap emission substantially avoids the reabsorption problem.

    View details for Web of Science ID A1981MD89800020

    View details for PubMedID 20333077

  • Correlation Function Analysis of Coherent Optical Transients and Fluorescence from a Quasi Two Level System Phys. Rev. A Skinner, J. L., Andersen, H. C., Fayer, M. D. 1981; 24: 1994-2008
  • DELOCALIZED ELECTRONIC EXCITATIONS OF PENTACENE DIMERS IN A PARA-TERPHENYL HOST - PICOSECOND PHOTON-ECHO EXPERIMENTS CHEMICAL PHYSICS LETTERS Olson, R. W., Patterson, F. G., Lee, H. W., Fayer, M. D. 1981; 79 (3): 403-407
  • LASER-INDUCED PHONON SPECTROSCOPY - OPTICAL-GENERATION OF ULTRASONIC-WAVES AND INVESTIGATION OF ELECTRONIC EXCITED-STATE INTERACTIONS IN SOLIDS PHYSICAL REVIEW B Nelson, K. A., LUTZ, D. R., Fayer, M. D., Madison, L. 1981; 24 (6): 3261-3275
  • NON-PHOTOCHEMICAL HOLE BURNING IN THE MIXED MOLECULAR-CRYSTAL PENTACENE IN BENZOIC-ACID CHEMICAL PHYSICS LETTERS Patterson, F. G., Lee, H. W., Olson, R. W., Fayer, M. D. 1981; 84 (1): 59-63
  • ELECTRONIC EXCITED-STATE TRANSPORT IN RANDOM-SYSTEMS - TIME-RESOLVED FLUORESCENCE DEPOLARIZATION MEASUREMENTS JOURNAL OF PHYSICAL CHEMISTRY Gochanour, C. R., Fayer, M. D. 1981; 85 (14): 1989-1994
  • ELECTRONIC EXCITED-STATE ENERGY-TRANSFER, TRAPPING BY DIMERS AND FLUORESCENCE QUENCHING IN CONCENTRATED DYE SOLUTIONS - PICOSECOND TRANSIENT GRATING EXPERIMENTS CHEMICAL PHYSICS LUTZ, D. R., Nelson, K. A., Gochanour, C. R., Fayer, M. D. 1981; 58 (3): 325-334
  • THEORY OF PHOTON-ECHOES FROM A PAIR OF COUPLED 2 LEVEL SYSTEMS - IMPURITY DIMERS AND ENERGY-TRANSFER IN MOLECULAR-CRYSTALS JOURNAL OF CHEMICAL PHYSICS Skinner, J. L., ANDERSEN, H. C., Fayer, M. D. 1981; 75 (7): 3195-3202
  • EXCITON SCATTERING AND THE DEPHASING OF ELECTRON-SPIN-RESONANCE AND OPTICAL-ABSORPTION LINES - THE 1,2,4,5-TETRACHLOROBENZENE TRIPLET EXCITON PROBLEM JOURNAL OF CHEMICAL PHYSICS WIETING, R. D., Fayer, M. D. 1980; 73 (2): 744-748
  • SITE-DEPENDENT VIBRONIC LINE WIDTHS AND RELAXATION IN THE MIXED MOLECULAR-CRYSTAL PENTACENE IN PARA-TERPHENYL JOURNAL OF PHYSICAL CHEMISTRY Olson, R. W., Fayer, M. D. 1980; 84 (16): 2001-2004
  • Exciton Scattering and the Dephasing of ESR and Optical Absorption Lines: The 1,2,4,5-tetrachlorobenzene Triplet Exciton Problem Chem. Phys. Wieting, R. D., Fayer, M. D. 1980; 73: 744-748
  • LASER-INDUCED PHONONS - A PROBE OF INTERMOLECULAR INTERACTIONS IN MOLECULAR-SOLIDS JOURNAL OF CHEMICAL PHYSICS Nelson, K. A., Fayer, M. D. 1980; 72 (9): 5202-5218
  • INTERMOLECULAR INTERACTION DYNAMICS AND OPTICAL DEPHASING - PICOSECOND PHOTON-ECHO MEASUREMENTS IN MIXED MOLECULAR-CRYSTALS JOURNAL OF CHEMICAL PHYSICS Cooper, D. E., Olson, R. W., Fayer, M. D. 1980; 72 (4): 2332-2339
  • EXCITED-STATE DYNAMICS IN PURE MOLECULAR-CRYSTALS - PERYLENE AND THE EXCIMER PROBLEM CHEMICAL PHYSICS LETTERS Nelson, K. A., Dlott, D. D., Fayer, M. D. 1979; 64 (1): 88-93
  • ELECTRONIC EXCITED-STATE TRANSPORT IN SOLUTION JOURNAL OF CHEMICAL PHYSICS Gochanour, C. R., ANDERSEN, H. C., Fayer, M. D. 1979; 70 (9): 4254-4271
  • PICOSECOND TIME SCALE OPTICAL COHERENCE EXPERIMENTS IN MIXED MOLECULAR-CRYSTALS - PENTACENE IN NAPHTHALENE CHEMICAL PHYSICS LETTERS Cooper, D. E., Olson, R. W., WIETING, R. D., Fayer, M. D. 1979; 67 (1): 41-47
  • EFFECTS OF IMPURITY SCATTERING AND TRANSPORT TOPOLOGY ON TRAPPING IN QUASI-ONE-DIMENSIONAL SYSTEMS - APPLICATION TO EXCITONS IN MOLECULAR-CRYSTALS JOURNAL OF CHEMICAL PHYSICS WIETING, R. D., Fayer, M. D., Dlott, D. D. 1978; 69 (5): 1996-2010
  • Dynamics of Energy Transport in Molecular Crystals: The Picosecond Transient- Grating Method Phys. Rev. Lett. Salcedo, J., Siegman, A. E., Dlott, D. D., Fayer, M. D. 1978; 41: 131-134
  • SPIN-LATTICE RELAXATION IN TRIPLET-STATES OF ISOLATED MOLECULES AND PURE CRYSTALS IN ZERO-FIELD JOURNAL OF CHEMICAL PHYSICS LUTZ, D. R., Nelson, K. A., Olson, R. W., Fayer, M. D. 1978; 69 (9): 4319-4321
  • Energy Transport in Molecular Solids: Application of the Picosecond Transient Grating Technique Picosecond Phenomena Dlott, D. D., Fayer, M. D., Salcedo, J., Siegman, A. E., Shapiro, S. L. edited by Shank, C. V., Ippen, E. P. Springer-Verlag, Berlin Heidelberg New York. 1978: 240
  • Effects of Impurity Scattering and Transport Topology on Exciton Migration and Trapping: An Experimental Study of Quasi-One-Dimensional Molecular Crystals J. Chem. Phys. Dlott, D. D., Fayer, M. D., Wieting, R. D., 1978; 69: 2752-2762
  • The Effects of Impurity Scattering and Transport Topology on Trapping in Quasi-One-Dimensional Transport Systems: Application to Excitons in Molecular Crystals J. Chem. Phys. Wieting, R. D., Fayer, M. D., Dlott, D. D. 1978; 69: 1996-2000
  • EFFECTS OF IMPURITY SCATTERING AND TRANSPORT TOPOLOGY ON EXCITON MIGRATION AND TRAPPING - EXPERIMENTAL-STUDY OF QUASI-ONE-DIMENSIONAL MOLECULAR-CRYSTALS JOURNAL OF CHEMICAL PHYSICS Dlott, D. D., Fayer, M. D., WIETING, R. D. 1978; 69 (6): 2752-2762
  • SPIN-ORBIT-COUPLING IN EXCITON BANDS OF MOLECULAR-CRYSTALS JOURNAL OF CHEMICAL PHYSICS Cooper, D. E., Fayer, M. D. 1978; 68 (1): 229-235
  • DYNAMICS OF ENERGY-TRANSPORT IN MOLECULAR-CRYSTALS - PICOSECOND TRANSIENT-GRATING METHOD PHYSICAL REVIEW LETTERS SALCEDO, J. R., Siegman, A. E., Dlott, D. D., Fayer, M. D. 1978; 41 (2): 131-134
  • TRIPLET EXCITON SPECTRAL-LINE SHAPES IN MOLECULAR-CRYSTALS - 1,2,4,5-TETRACHLOROBENZENE CHEMICAL PHYSICS LETTERS BURLAND, D. M., Cooper, D. E., Fayer, M. D., Gochanour, C. R. 1977; 52 (2): 279-284
  • COHERENT ONE-DIMENSIONAL EXCITON TRANSPORT AND IMPURITY SCATTERING JOURNAL OF CHEMICAL PHYSICS Dlott, D. D., Fayer, M. D., WIETING, R. D. 1977; 67 (8): 3808-3817
  • EXPERIMENTAL-DETERMINATION OF TRIPLET EXCITON INTERMOLECULAR INTERACTION MATRIX ELEMENT AND EXCITON-PHONON SCATTERING RATE IN MOLECULAR-CRYSTALS CHEMICAL PHYSICS LETTERS Dlott, D. D., Fayer, M. D. 1976; 41 (2): 305-310
  • Coherence in Multilevel Systems. II. Description of a Multilevel System as Two Levels in Contact with a Population Reservoir Phys. Rev. A Breinland, W. G., Fayer, M. D., Harris, C. B. 1976; 13: 383
  • Experimental Determination of the Triplet Exciton Intermolecular Interaction Matrix Element and the Exciton-Phonon Scattering Rate in Molecular Crystals Chem. Phys. Lett. Dlott, D. D., Fayer, M. D. 1976; 41: 305-310
  • COHERENCE IN MULTILEVEL SYSTEMS .2. DESCRIPTION OF A MULTILEVEL SYSTEM AS 2 LEVELS IN CONTACT WITH A POPULATION RESERVOIR PHYSICAL REVIEW A Breiland, W. G., Fayer, M. D., Harris, C. B. 1976; 13 (1): 383-395
  • On the Temperature Dependence of Excited Triplet State Spin Sublevel Populations of Shallow Traps in Molecular Crystals J. Chem. Phys. Fayer, M. D., Gochanour, C. R. 1976; 65`: 2472-2473
  • Direct Measurement of the Quantum Yield for the Creation of Mobile Excitons from Localized States Using Optically Detected Electron Spin Coherence Chem. Phys. Lett. Banner, H. C., Brock, J. C., Fayer, M. D., Harris, C. B. 1975; 33: 471-476
  • DIRECT MEASUREMENT OF QUANTUM YIELD FOR CREATION OF MOBILE EXCITONS FROM LOCALIZED STATES USING OPTICALLY DETECTED ELECTRON-SPIN COHERENCE CHEMICAL PHYSICS LETTERS Brenner, H. C., Brock, J. C., Fayer, M. D., Harris, C. B. 1975; 33 (3): 471-476
  • Coherent Energy Migration in Solids I. Band-Trap Equilibria at Boltzmann and Non-Boltzmann Temperatures Phys. Rev. B Fayer, M. D., Harris, C. B. 1974; 9: 748-796
  • COHERENT ENERGY MIGRATION IN SOLIDS .1. BAND-TRAP EQUILIBRIA AT BOLTZMANN AND NONBOLTZMANN TEMPERATURES PHYSICAL REVIEW B Fayer, M. D., Harris, C. B. 1974; 9 (2): 748-769
  • DECAY OF LOCALIZED STATES INTO DELOCALIZED BAND STATES - THEORY AND PRELIMINARY EXPERIMENTAL INVESTIGATIONS USING OPTICALLY DETECTED ELECTRON-SPIN COHERENCE CHEMICAL PHYSICS LETTERS Fayer, M. D., Harris, C. B. 1974; 25 (2): 149-157
  • The Decay of Localized States Into Delocalized Band States. Theory and Preliminary Experimental Investigations Using Optically Detected Electron Spin Coherence Chem. Phys. Lett. Fayer, M. D., Harris, C. B. 1974; 25: 149-157
  • COHERENT ENERGY MIGRATION IN SOLIDS .2. SPIN-RESONANCE ABSORPTION IN COHERENT-WAVE-PACKET STATES AND EFFECTS OF PHONON-EXCITON SCATTERING PHYSICAL REVIEW B Harris, C. B., Fayer, M. D. 1974; 10 (5): 1784-1800
  • Coherent Energy Migration in Solids II. Spin Resonance Absorption in Coherent Wave Packet States and the Effects of Phonon-Exciton Scattering Phys. Rev. B Harris, C. B., Fayer, M. D. 1974; 9 (2): 748-769
  • OPTICALLY DETECTED NUCLEAR QUADRUPOLE RESONANCE AND TRANSFERRED HYPERFINE COUPLING VIA GUEST-HOST INTERACTIONS IN MOLECULAR CRYSTALS JOURNAL OF CHEMICAL PHYSICS Fayer, M. D., Harris, C. B., Yuen, D. A. 1970; 53 (12): 4719-?
  • Transition Metal Nuclear Quadrupole Resonance IV. Manganese--55 Nuclear Quadrupole Resonance in π-Pyrrolenylmanganese Tricarbonyl and π-Cyclopentadienylmanganese Tricarbonyl and π-Pyrrolenyl-Metal Bonds Inorganic Chemistry Fayer, M. D., Harris, C. B. 1969; 8: 2792-2796
  • TRANSITION METAL NUCLEAR QUADRUPOLE RESONANCE .4. MANGANESE-55 NUCLEAR QUADRUPOLE RESONANCE IN PI-PYRROLENYLMANGANESE TRICARBONYL AND PI-CYCLOPENTADIENYLMANGANESE TRICARBONYL AND PI-PYRROLENYL-METAL BONDS INORGANIC CHEMISTRY Fayer, M. D., Harris, C. B. 1969; 8 (12): 2792-?