Joseph Stephen Robinson

All Publications

• The Linac Coherent Light Source II photoinjector laser infrastructure HIGH POWER LASER SCIENCE AND ENGINEERING Zhang, H., Gilevich, S., Miahnahri, A., Alverson, S., Brachmann, A., Duris, J., Franz, P., Fry, A., Hirschman, J., Larsen, K., Lemons, R., Li, S., Lu, B., Marinelli, A., Martinez, M., May, J., Milshtein, E., Murari, K., Neveu, N., Robinson, J., Schmerge, J., Sun, L., Vecchione, T., Xu, C., Zhou, F., Carbajo, S. 2024; 12

  View details for DOI 10.1017/hpl.2024.33

  View details for Web of Science ID 001318028000001

• Characterization of Deformational Isomerization Potential and Interconversion Dynamics with Ultrafast X-ray Solution Scattering. Journal of the American Chemical Society Powers-Riggs, N. E., Birgisson, B. O., Raj, S. L., Biasin, E., Lenzen, P., Zederkof, D. B., Haubro, M., Tveiten, D. K., Hartsock, R. W., van Driel, T. B., Kunnus, K., Chollet, M., Robinson, J. S., Nelson, S., Forbes, R., Haldrup, K., Pedersen, K. S., Levi, G., Ougaard Dohn, A., Jonsson, H., Mo Ller, K. B., Natan, A., Nielsen, M. M., Gaffney, K. J. 2024

  Abstract

  Dimeric complexes composed of d8 square planar metal centers and rigid bridging ligands provide model systems to understand the interplay between attractive dispersion forces and steric strain in order to assist the development of reliable methods to model metal dimer complexes more broadly. [Ir2 (dimen)4]2+ (dimen = para-diisocyanomenthane) presents a unique case study for such phenomena, as distortions of the optimal structure of a ligand with limited conformational flexibility counteract the attractive dispersive forces from the metal and ligand to yield a complex with two ground state deformational isomers. Here, we use ultrafast X-ray solution scattering (XSS) and optical transient absorption spectroscopy (OTAS) to reveal the nature of the equilibrium distribution and the exchange rate between the deformational isomers. The two ground state isomers have spectrally distinct electronic excitations that enable the selective excitation of one isomer or the other using a femtosecond duration pulse of visible light. We then track the dynamics of the nonequilibrium depletion of the electronic ground state population─often termed the ground state hole─with ultrafast XSS and OTAS, revealing a restoration of the ground state equilibrium in 2.3 ps. This combined experimental and theoretical study provides a critical test of various density functional approximations in the description of bridged d8-d8 metal complexes. The results show that density functional theory calculations can reproduce the primary experimental observations if dispersion interactions are added, and a hybrid functional, which includes exact exchange, is used.

  View details for DOI 10.1021/jacs.4c00817

  View details for PubMedID 38727611

• The Ring-Closing Reaction of Cyclopentadiene Probed with Ultrafast X-ray Scattering. The journal of physical chemistry. A Huang, L., Bertram, L., Ma, L., Goff, N., Crane, S. W., Odate, A., Northey, T., Carrascosa, A. M., Simmermacher, M., Muvva, S. B., Geiser, J. D., Lueckheide, M. J., Phelps, Z., Liang, M., Cheng, X., Forbes, R., Robinson, J. S., Hayes, M. J., Allum, F., Green, A. E., Lopata, K., Rudenko, A., Wolf, T. J., Centurion, M., Rolles, D., Minitti, M. P., Kirrander, A., Weber, P. M. 2024

  Abstract

  The dynamics of cyclopentadiene (CP) following optical excitation at 243 nm was investigated by time-resolved pump-probe X-ray scattering using 16.2 keV X-rays at the Linac Coherent Light Source (LCLS). We present the first ultrafast structural evidence that the reaction leads directly to the formation of bicyclo[2.1.0]pentene (BP), a strained molecule with three- and four-membered rings. The bicyclic compound decays via a thermal backreaction to the vibrationally hot CP with a time constant of 21 ± 3 ps. A minor channel leads to ring-opened structures on a subpicosecond time scale.

  View details for DOI 10.1021/acs.jpca.4c02509

  View details for PubMedID 38709555

• Tracking Cavity Formation in Electron Solvation: Insights from X-ray Spectroscopy and Theory JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Sopena Moros, A., Li, S., Li, K., Doumy, G., Southworth, S. H., Otolski, C., Schaller, R. D., Kumagai, Y., Rubensson, J., Simon, M., Dakovski, G., Kunnus, K., Robinson, J. S., Hampton, C. Y., Hoffman, D. J., Koralek, J., Loh, Z., Santra, R., Inhester, L., Young, L. 2024; 146 (5): 3262-3269

  Abstract

  We present time-resolved X-ray absorption spectra of ionized liquid water and demonstrate that OH radicals, H3O+ ions, and solvated electrons all leave distinct X-ray-spectroscopic signatures. Particularly, this allows us to characterize the electron solvation process through a tool that focuses on the electronic response of oxygen atoms in the immediate vicinity of a solvated electron. Our experimental results, supported by ab initio calculations, confirm the formation of a cavity in which the solvated electron is trapped. We show that the solvation dynamics are governed by the magnitude of the random structural fluctuations present in water. As a consequence, the solvation time is highly sensitive to temperature and to the specific way the electron is injected into water.

  View details for DOI 10.1021/jacs.3c11857

  View details for Web of Science ID 001158517400001

  View details for PubMedID 38270463

  View details for PubMedCentralID PMC10859959

• Hard x-ray - optical four-wave mixing using a split-and-delay line OPTICS EXPRESS Peters, W. K., Feltman, J., Jones, T., Song, S., Chollet, M., Robinson, J., Padmanabhan, P., Foglia, L., Bencivenga, F., Coffee, R., Bowlan, P. 2023; 31 (19): 31410-31418

  View details for DOI 10.1364/OE.485287

  View details for Web of Science ID 001106628300001

• Ferricyanide photo-aquation pathway revealed by combined femtosecond Kβ main line and valence-to-core x-ray emission spectroscopy. Nature communications Reinhard, M., Gallo, A., Guo, M., Garcia-Esparza, A. T., Biasin, E., Qureshi, M., Britz, A., Ledbetter, K., Kunnus, K., Weninger, C., van Driel, T., Robinson, J., Glownia, J. M., Gaffney, K. J., Kroll, T., Weng, T. C., Alonso-Mori, R., Sokaras, D. 2023; 14 (1): 2443

  Abstract

  Reliably identifying short-lived chemical reaction intermediates is crucial to elucidate reaction mechanisms but becomes particularly challenging when multiple transient species occur simultaneously. Here, we report a femtosecond x-ray emission spectroscopy and scattering study of the aqueous ferricyanide photochemistry, utilizing the combined Fe Kβ main and valence-to-core emission lines. Following UV-excitation, we observe a ligand-to-metal charge transfer excited state that decays within 0.5 ps. On this timescale, we also detect a hitherto unobserved short-lived species that we assign to a ferric penta-coordinate intermediate of the photo-aquation reaction. We provide evidence that bond photolysis occurs from reactive metal-centered excited states that are populated through relaxation of the charge transfer excited state. Beyond illuminating the elusive ferricyanide photochemistry, these results show how current limitations of Kβ main line analysis in assigning ultrafast reaction intermediates can be circumvented by simultaneously using the valence-to-core spectral range.

  View details for DOI 10.1038/s41467-023-37922-x

  View details for PubMedID 37147295

  View details for PubMedCentralID 16604

• The DREAM Endstation at the Linac Coherent Light Source APPLIED SCIENCES-BASEL Walter, P., Holmes, M., Obaid, R., Amores, L., Cheng, X., Cryan, J. P., Glownia, J. M., Li, X., Lin, M., Ng, M., Robinson, J., Shivaram, N., Yin, J., Fritz, D., James, J., Castagna, J., Osipov, T. 2022; 12 (20)

  View details for DOI 10.3390/app122010534

  View details for Web of Science ID 000874182200001

• The time-resolved atomic, molecular and optical science instrument at the Linac Coherent Light Source. Journal of synchrotron radiation Walter, P., Osipov, T., Lin, M. F., Cryan, J., Driver, T., Kamalov, A., Marinelli, A., Robinson, J., Seaberg, M. H., Wolf, T. J., Aldrich, J., Brown, N., Champenois, E. G., Cheng, X., Cocco, D., Conder, A., Curiel, I., Egger, A., Glownia, J. M., Heimann, P., Holmes, M., Johnson, T., Lee, L., Li, X., Moeller, S., Morton, D. S., Ng, M. L., Ninh, K., O'Neal, J. T., Obaid, R., Pai, A., Schlotter, W., Shepard, J., Shivaram, N., Stefan, P., Van, X., Wang, A. L., Wang, H., Yin, J., Yunus, S., Fritz, D., James, J., Castagna, J. C. 2022; 29 (Pt 4): 957-968

  Abstract

  The newly constructed time-resolved atomic, molecular and optical science instrument (TMO) is configured to take full advantage of both linear accelerators at SLAC National Accelerator Laboratory, the copper accelerator operating at a repetition rate of 120 Hz providing high per-pulse energy as well as the superconducting accelerator operating at a repetition rate of about 1 MHz providing high average intensity. Both accelerators power a soft X-ray free-electron laser with the new variable-gap undulator section. With this flexible light source, TMO supports many experimental techniques not previously available at LCLS and will have two X-ray beam focus spots in line. Thereby, TMO supports atomic, molecular and optical, strong-field and nonlinear science and will also host a designated new dynamic reaction microscope with a sub-micrometer X-ray focus spot. The flexible instrument design is optimized for studying ultrafast electronic and molecular phenomena and can take full advantage of the sub-femtosecond soft X-ray pulse generation program.

  View details for DOI 10.1107/S1600577522004283

  View details for PubMedID 35787561

• Clocking Auger electrons NATURE PHYSICS Haynes, D. C., Wurzer, M., Schletter, A., Al-Haddad, A., Blaga, C., Bostedt, C., Bozek, J., Bromberger, H., Bucher, M., Camper, A., Carron, S., Coffee, R., Costello, J. T., DiMauro, L. F., Ding, Y., Ferguson, K., Grguras, I., Helml, W., Hoffmann, M. C., Ilchen, M., Jalas, S., Kabachnik, N. M., Kazansky, A. K., Kienberger, R., Maier, A. R., Maxwell, T., Mazza, T., Meyer, M., Park, H., Robinson, J., Roedig, C., Schlarb, H., Singla, R., Tellkamp, F., Walker, P. A., Zhang, K., Doumy, G., Behrens, C., Cavalieri, A. L. 2021; 17 (4): 512-+

  View details for DOI 10.1038/s41567-020-01111-0

  View details for Web of Science ID 000608659800002

• Integrated structured light architectures. Scientific reports Lemons, R., Liu, W., Frisch, J. C., Fry, A., Robinson, J., Smith, S. R., Carbajo, S. 2021; 11 (1): 796

  Abstract

  The structural versatility of light underpins an outstanding collection of optical phenomena where both geometrical and topological states of light can dictate how matter will respond or display. Light possesses multiple degrees of freedom such as amplitude, and linear, spin angular, and orbital angular momenta, but the ability to adaptively engineer the spatio-temporal distribution of all these characteristics is primarily curtailed by technologies used to impose any desired structure to light. We demonstrate a laser architecture based on coherent beam combination offering integrated spatio-temporal field control and programmability, thereby presenting unique opportunities for generating light by design to exploit its topology.

  View details for DOI 10.1038/s41598-020-80502-y

  View details for PubMedID 33436972

• Ultrafast X-ray scattering offers a structural view of excited-state charge transfer. Proceedings of the National Academy of Sciences of the United States of America Yong, H. n., Xu, X. n., Ruddock, J. M., Stankus, B. n., Carrascosa, A. M., Zotev, N. n., Bellshaw, D. n., Du, W. n., Goff, N. n., Chang, Y. n., Boutet, S. n., Carbajo, S. n., Koglin, J. E., Liang, M. n., Robinson, J. S., Kirrander, A. n., Minitti, M. P., Weber, P. M. 2021; 118 (19)

  Abstract

  Intramolecular charge transfer and the associated changes in molecular structure in N,N'-dimethylpiperazine are tracked using femtosecond gas-phase X-ray scattering. The molecules are optically excited to the 3p state at 200 nm. Following rapid relaxation to the 3s state, distinct charge-localized and charge-delocalized species related by charge transfer are observed. The experiment determines the molecular structure of the two species, with the redistribution of electron density accounted for by a scattering correction factor. The initially dominant charge-localized state has a weakened carbon-carbon bond and reorients one methyl group compared with the ground state. Subsequent charge transfer to the charge-delocalized state elongates the carbon-carbon bond further, creating an extended 1.634 Å bond, and also reorients the second methyl group. At the same time, the bond lengths between the nitrogen and the ring-carbon atoms contract from an average of 1.505 to 1.465 Å. The experiment determines the overall charge transfer time constant for approaching the equilibrium between charge-localized and charge-delocalized species to 3.0 ps.

  View details for DOI 10.1073/pnas.2021714118

  View details for PubMedID 33947814

• Hard X-ray-Optical Transient Grating Peters, W., Jones, T., Song, S., Chollet, M., Robinson, J., Foglia, L., Bencivenga, F., Coffee, R., Bowlan, P., IEEE IEEE. 2021

  View details for Web of Science ID 000831479803163

• Arrival Time Monitor for Sub-10 fs Soft X-ray and 800 nm Optical Pulses Muhammad, I., Frimpong, B., Daafour, J., Xu, X., Walter, P., Wolf, T. A., Cryan, J. P., Glownia, J. M., Robinson, J. S., Droste, S., Coslovich, G., IEEE IEEE. 2021

  View details for Web of Science ID 000831479802212

• Ultrafast structural changes within a photosynthetic reaction centre. Nature Dods, R., Bath, P., Morozov, D., Gagner, V. A., Arnlund, D., Luk, H. L., Kubel, J., Maj, M., Vallejos, A., Wickstrand, C., Bosman, R., Beyerlein, K. R., Nelson, G., Liang, M., Milathianaki, D., Robinson, J., Harimoorthy, R., Berntsen, P., Malmerberg, E., Johansson, L., Andersson, R., Carbajo, S., Claesson, E., Conrad, C. E., Dahl, P., Hammarin, G., Hunter, M. S., Li, C., Lisova, S., Royant, A., Safari, C., Sharma, A., Williams, G. J., Yefanov, O., Westenhoff, S., Davidsson, J., DePonte, D. P., Boutet, S., Barty, A., Katona, G., Groenhof, G., Branden, G., Neutze, R. 2020

  Abstract

  Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.

  View details for DOI 10.1038/s41586-020-3000-7

  View details for PubMedID 33268896

• Femtosecond quantification of void evolution during rapid material failure SCIENCE ADVANCES Coakley, J., Higginbotham, A., McGonegle, D., Ilavsky, J., Swinburne, T. D., Wark, J. S., Rahman, K. M., Vorontsov, V. A., Dye, D., Lane, T. J., Boutet, S., Koglin, J., Robinson, J., Milathianaki, D. 2020; 6 (51)

  Abstract

  Understanding high-velocity impact, and the subsequent high strain rate material deformation and potential catastrophic failure, is of critical importance across a range of scientific and engineering disciplines that include astrophysics, materials science, and aerospace engineering. The deformation and failure mechanisms are not thoroughly understood, given the challenges of experimentally quantifying material evolution at extremely short time scales. Here, copper foils are rapidly strained via picosecond laser ablation and probed in situ with femtosecond x-ray free electron (XFEL) pulses. Small-angle x-ray scattering (SAXS) monitors the void distribution evolution, while wide-angle scattering (WAXS) simultaneously determines the strain evolution. The ability to quantifiably characterize the nanoscale during high strain rate failure with ultrafast SAXS, complementing WAXS, represents a broadening in the range of science that can be performed with XFEL. It is shown that ultimate failure occurs via void nucleation, growth, and coalescence, and the data agree well with molecular dynamics simulations.

  View details for DOI 10.1126/sciadv.abb4434

  View details for Web of Science ID 000599905500005

  View details for PubMedID 33328222

  View details for PubMedCentralID PMC7744076

• High-sensitivity x-ray/optical cross-correlator for next generation free-electron lasers OPTICS EXPRESS Droste, S., Zohar, S., Shen, L., White, V. E., Diaz-Jacobo, E., Coffee, R. N., Reid, A. H., Tavella, F., Minitti, M. P., Turner, J. J., Robinson, J. S., Fry, A. R., Coslovich, G. 2020; 28 (16): 23545–53

  Abstract

  We design and realize an arrival time diagnostic for ultrashort X-ray pulses achieving unprecedented high sensitivity in the soft X-ray regime via cross-correlation with a ≈1550 nm optical laser. An interferometric detection scheme is combined with a multi-layer sample design to greatly improve the sensitivity of the measurement. We achieve up to 275% of relative signal change when exposed to 1.6 mJ/cm2 of soft X-rays at 530 eV, more than a hundred-fold improvement in sensitivity as compared to previously reported techniques. The resolution of the arrival time measurement is estimated to around 2.8 fs (rms). The demonstrated X-ray arrival time monitor paves the way for sub-10 fs-level timing jitter at high repetition rate X-ray facilities.

  View details for DOI 10.1364/OE.398048

  View details for Web of Science ID 000560931200042

  View details for PubMedID 32752349

• Observation of the molecular response to light upon photoexcitation. Nature communications Yong, H., Zotev, N., Ruddock, J. M., Stankus, B., Simmermacher, M., Carrascosa, A. M., Du, W., Goff, N., Chang, Y., Bellshaw, D., Liang, M., Carbajo, S., Koglin, J. E., Robinson, J. S., Boutet, S., Minitti, M. P., Kirrander, A., Weber, P. M. 2020; 11 (1): 2157

  Abstract

  When a molecule interacts with light, its electrons can absorb energy from the electromagnetic field by rapidly rearranging their positions. This constitutes the first step of photochemical and photophysical processes that include primary events in human vision and photosynthesis. Here, we report the direct measurement of the initial redistribution of electron density when the molecule 1,3-cyclohexadiene (CHD) is optically excited. Our experiments exploit the intense, ultrashort hard x-ray pulses of the Linac Coherent Light Source (LCLS) to map the change in electron density using ultrafast x-ray scattering. The nature of the excited electronic state is identified with excellent spatial resolution and in good agreement with theoretical predictions. The excited state electron density distributions are thus amenable to direct experimental observation.

  View details for DOI 10.1038/s41467-020-15680-4

  View details for PubMedID 32358535

• X-ray diffractive imaging of controlled gas-phase molecules: Toward imaging of dynamics in the molecular frame. The Journal of chemical physics Kierspel, T., Morgan, A., Wiese, J., Mullins, T., Aquila, A., Barty, A., Bean, R., Boll, R., Boutet, S., Bucksbaum, P., Chapman, H. N., Christensen, L., Fry, A., Hunter, M., Koglin, J. E., Liang, M., Mariani, V., Natan, A., Robinson, J., Rolles, D., Rudenko, A., Schnorr, K., Stapelfeldt, H., Stern, S., Thogersen, J., Yoon, C. H., Wang, F., Kupper, J. 2020; 152 (8): 084307

  Abstract

  We report experimental results on the diffractive imaging of three-dimensionally aligned 2,5-diiodothiophene molecules. The molecules were aligned by chirped near-infrared laser pulses, and their structure was probed at a photon energy of 9.5 keV (lambda 130 pm) provided by the Linac Coherent Light Source. Diffracted photons were recorded on the Cornell-SLAC pixel array detector, and a two-dimensional diffraction pattern of the equilibrium structure of 2,5-diiodothiophene was recorded. The retrieved distance between the two iodine atoms agrees with the quantum-chemically calculated molecular structure to be within 5%. The experimental approach allows for the imaging of intrinsic molecular dynamics in the molecular frame, albeit this requires more experimental data, which should be readily available at upcoming high-repetition-rate facilities.

  View details for DOI 10.1063/1.5133963

  View details for PubMedID 32113333

• Megahertz-compatible angular streaking with few-femtosecond resolution at x-ray free-electron lasers PHYSICAL REVIEW A Heider, R., Wagner, M. S., Hartmann, N., Ilchen, M., Buck, J., Hartmann, G., Shirvanyan, Lindahl, A. O., Gruenert, J., Krzywinski, J., Liu, J., Ossiander, M., Lutman, A. A., Maxwell, T., Miahnahri, A. A., Moeller, S. P., Planas, M., Robinson, J., Viefhaus, J., Feurer, T., Kienberger, R., Coffee, R. N., Helml, W. 2019; 100 (5)

  View details for DOI 10.1103/PhysRevA.100.053420

  View details for Web of Science ID 000498843300012

• 100 W high-repetition-rate near-infrared optical parametric chirped pulse amplifier OPTICS LETTERS Windeler, M. R., Mecseki, K., Miahnahri, A., Robinson, J. S., Fraser, J. M., Fry, A. R., Tavella, F. 2019; 44 (17): 4287-4290

  Abstract

  New high-repetition-rate x-ray free electron lasers (XFELs) require for their operation highly reliable ultrafast laser systems with high pulse energy, high repetition rate, and high average power. In this Letter, we present high-average-power scaling of near-infrared optical parametric chirped pulse amplification (OPCPA) in potassium titanyl arsenate (KTA) with tunable center wavelengths from 1.5 to 2.0 μm. Using a three-stage amplification scheme and a kW-level InnoSlab Yb:YAG pump amplifier for the final non-collinear KTA stage, we demonstrate an amplified output power of 106.2 W at a center wavelength of 1.75 μm and 100 kHz. Idler absorption introduces a potential upper limit on the average power scaling of center wavelengths <1.70  μm. Future scaling of average power to hundreds of Watts is possible at center wavelengths ≥1.70  μm.

  View details for DOI 10.1364/OL.44.004287

  View details for Web of Science ID 000483918900050

  View details for PubMedID 31465384

• Ultrafast X-ray scattering reveals vibrational coherence following Rydberg excitation. Nature chemistry Stankus, B., Yong, H., Zotev, N., Ruddock, J. M., Bellshaw, D., Lane, T. J., Liang, M., Boutet, S., Carbajo, S., Robinson, J. S., Du, W., Goff, N., Chang, Y., Koglin, J. E., Minitti, M. P., Kirrander, A., Weber, P. M. 2019

  Abstract

  The coherence and dephasing of vibrational motions of molecules constitute an integral part of chemical dynamics, influence material properties and underpin schemes to control chemical reactions. Considerable progress has been made in understanding vibrational coherence through spectroscopic measurements, but precise, direct measurement of the structure of a vibrating excited-state polyatomic organic molecule has remained unworkable. Here, we measure the time-evolving molecular structure of optically excited N-methylmorpholine through scattering with ultrashort X-ray pulses. The scattering signals are corrected for the differences in electron density in the excited electronic state of the molecule in comparison to the ground state. The experiment maps the evolution of the molecular geometry with femtosecond resolution, showing coherent motion that survives electronic relaxation and seems to persist for longer than previously seen using other methods.

  View details for DOI 10.1038/s41557-019-0291-0

  View details for PubMedID 31285542

• Pulse contrast enhancement via non-collinear sum-frequency generation with the signal and idler of an optical parametric amplifier APPLIED PHYSICS LETTERS Cunningham, E., Galtier, E., Dyer, G., Robinson, J., Fry, A. 2019; 114 (22)

  View details for DOI 10.1063/1.5108911

  View details for Web of Science ID 000470718700037

• Generation of high-intensity ultrasound through shock propagation in liquid jets PHYSICAL REVIEW FLUIDS Blaj, G., Liang, M., Aquila, A. L., Willmott, P. R., Koglin, J. E., Sierra, R. G., Robinson, J. S., Boutet, S., Stan, C. A. 2019; 4 (4)

  View details for DOI 10.1103/PhysRevFluids.4.043401

  View details for Web of Science ID 000464760200001

• High average power 88 W OPCPA system for high-repetition-rate experiments at the LCLS x-ray free-electron laser OPTICS LETTERS Mecseki, K., Windeler, M. R., Miahnahri, A., Robinson, J. S., Fraser, J. M., Fry, A. R., Tavella, F. 2019; 44 (5): 1257-1260

  Abstract

  We present a 100 kHz, sub-20 fs optical parametric chirped-pulse amplifier (OPCPA) system delivering 88.6 W average power at a center wavelength of 800 nm. The seed pulses are derived from the pump laser via white-light continuum generation and are amplified in three non-collinear OPCPA stages. The final two high-power stages are pumped with a 661 W Yb:YAG InnoSlab amplifier. A simple and robust design is used for the OPCPA system to avoid thermal effects and enhance long-term stability, resulting in excellent beam quality and high conversion efficiency. To the best of our knowledge, this is the highest average power OPCPA system reported to date.

  View details for DOI 10.1364/OL.44.001257

  View details for Web of Science ID 000460109200048

  View details for PubMedID 30821762

• Programmable Control of Femtosecond Structured Light Lemons, R., Liu, W., Durfee, C. G., Frisch, J. C., Smith, S., Robinson, J., Fry, A., Carbajo, S., IEEE IEEE. 2019

  View details for Web of Science ID 000482226303090

• Thermal effects in a high repetition rate 88 W average power OPCPA system at 800 nm Mecseki, K., Windeler, M. R., Robinson, J. S., Fraser, J. M., Fry, A. R., Tavella, F., Awwal, A. A., Haefner, C. L. SPIE-INT SOC OPTICAL ENGINEERING. 2019

  View details for DOI 10.1117/12.2523978

  View details for Web of Science ID 000468813700013

• Pulse Contrast Enhancement via Non-collinear Sum-Frequency Generation of the Signal and Idler of an Optical Parametric Amplifier Cunningham, E., Galtier, E., Dyer, G., Robinson, J., Fry, A., IEEE IEEE. 2019

  View details for Web of Science ID 000482226300180

• High Power dual-mode IR and NIR OPCPA Mecseki, K., Windeler, M. R., Prandolini, M. J., Robinson, J. S., Fraser, J. M., Fry, A. R., Tavella, F., Hein, J., Butcher, T. J. SPIE-INT SOC OPTICAL ENGINEERING. 2019

  View details for DOI 10.1117/12.2524517

  View details for Web of Science ID 000483017000011

• A deep UV trigger for ground-state ring-opening dynamics of 1,3-cyclohexadiene. Science advances Ruddock, J. M., Yong, H. n., Stankus, B. n., Du, W. n., Goff, N. n., Chang, Y. n., Odate, A. n., Carrascosa, A. M., Bellshaw, D. n., Zotev, N. n., Liang, M. n., Carbajo, S. n., Koglin, J. n., Robinson, J. S., Boutet, S. n., Kirrander, A. n., Minitti, M. P., Weber, P. M. 2019; 5 (9): eaax6625

  Abstract

  We explore the photo-induced kinetics of 1,3-cyclohexadiene upon excitation at 200 nm to the 3p state by ultrafast time-resolved, gas-phase x-ray scattering using the Linac Coherent Light Source. Analysis of the scattering anisotropy reveals that the excitation leads to the 3px and 3py Rydberg electronic states, which relax to the ground state with a time constant of 208 ± 11 fs. In contrast to the well-studied 266 nm excitation, at 200 nm the majority of the molecules (76 ± 3%) relax to vibrationally hot cyclohexadiene in the ground electronic state. A subsequent reaction on the ground electronic state surface leads from the hot cyclohexadiene to 1,3,5-hexatriene, with rates for the forward and backward reactions of 174 ± 13 and 355 ± 45 ps, respectively. The scattering pattern of the final hexatriene product reveals a thermal distribution of rotamers about the carbon-carbon single bonds.

  View details for DOI 10.1126/sciadv.aax6625

  View details for PubMedID 31523713

  View details for PubMedCentralID PMC6731073

• Scattering off molecules far from equilibrium. The Journal of chemical physics Yong, H. n., Ruddock, J. M., Stankus, B. n., Ma, L. n., Du, W. n., Goff, N. n., Chang, Y. n., Zotev, N. n., Bellshaw, D. n., Boutet, S. n., Carbajo, S. n., Koglin, J. E., Liang, M. n., Robinson, J. S., Kirrander, A. n., Minitti, M. P., Weber, P. M. 2019; 151 (8): 084301

  Abstract

  Pump-probe gas phase X-ray scattering experiments, enabled by the development of X-ray free electron lasers, have advanced to reveal scattering patterns of molecules far from their equilibrium geometry. While dynamic displacements reflecting the motion of wavepackets can probe deeply into the reaction dynamics, in many systems, the thermal excitation embedded in the molecules upon optical excitation and energy randomization can create systems that encompass structures far from the ground state geometry. For polyatomic molecular systems, large amplitude vibrational motions are associated with anharmonicity and shifts of interatomic distances, making analytical solutions using traditional harmonic approximations inapplicable. More generally, the interatomic distances in a polyatomic molecule are not independent and the traditional equations commonly used to interpret the data may give unphysical results. Here, we introduce a novel method based on molecular dynamic trajectories and illustrate it on two examples of hot, vibrating molecules at thermal equilibrium. When excited at 200 nm, 1,3-cyclohexadiene (CHD) relaxes on a subpicosecond time scale back to the reactant molecule, the dominant pathway, and to various forms of 1,3,5-hexatriene (HT). With internal energies of about 6 eV, the energy thermalizes quickly, leading to structure distributions that deviate significantly from their vibrationless equilibrium. The experimental and theoretical results are in excellent agreement and reveal that a significant contribution to the scattering signal arises from transition state structures near the inversion barrier of CHD. In HT, our analysis clarifies that previous inconsistent structural parameters determined by electron diffraction were artifacts that might have resulted from the use of inapplicable analytical equations.

  View details for DOI 10.1063/1.5111979

  View details for PubMedID 31470697

• Determining Orientations of Optical Transition Dipole Moments Using Ultrafast X-ray Scattering JOURNAL OF PHYSICAL CHEMISTRY LETTERS Yong, H., Zotev, N., Stankus, B., Ruddock, J. M., Bellshaw, D., Boutet, S., Lane, T. J., Liang, M., Carbajo, S., Robinson, J. S., Du, W., Goff, N., Chang, Y., Koglin, J. E., Waters, M. J., Solling, T. I., Minitti, M. P., Kirrander, A., Weber, P. M. 2018; 9 (22): 6556–62

  View details for DOI 10.1021/acs.jpclett.8b02773

  View details for Web of Science ID 000451362100027

• Hard X-ray induced fast secondary electron cascading processes in solids APPLIED PHYSICS LETTERS Mecseki, K., Hoeppner, H., Buescher, M., Tkachenko, V., Medvedev, N., Bekx, J. J., Lipp, V., Piekarz, P., Windeler, M., Tisch, J. G., Walke, D. J., Nakatsutsumi, M., Prandolini, M. J., Glownia, J. M., Sato, T., Sikorski, M., Chollet, M., Teubner, U., Robinson, J., Toleikis, S., Ziaja, B., Tavella, F. 2018; 113 (11)

  View details for DOI 10.1063/1.5046070

  View details for Web of Science ID 000444756300042

• Attosecond time-energy structure of X-ray free-electron laser pulses NATURE PHOTONICS Hartmann, N., Hartmann, G., Heider, R., Wagner, M. S., Ilchen, M., BucK, J., Lindahl, A. O., Benko, C., Gruenert, J., Krzywinski, J., Liu, J., Lutman, A. A., Marinelli, A., Maxwell, T., Miahnahri, A. A., Moeller, S. P., Planas, M., Robinson, J., Kazansky, A. K., Kabachnik, N. M., Viefhaus, J., Feurer, T., Kienberger, R., Coffee, R. N., Helml, W. 2018; 12 (4): 215-+

  View details for DOI 10.1038/s41566-018-0107-6

  View details for Web of Science ID 000428785500014

• Femtosecond X-ray diffraction from an aerosolized beam of protein nanocrystals JOURNAL OF APPLIED CRYSTALLOGRAPHY Awel, S., Kirian, R. A., Wiedorn, M. O., Beyerlein, K. R., Roth, N., Horke, D. A., Oberthuer, D., Knoska, J., Mariani, V., Morgan, A., Adriano, L., Tolstikova, A., Xavier, P., Yefanov, O., Aquila, A., Barty, A., Roy-Chowdhury, S., Hunter, M. S., James, D., Robinson, J. S., Weierstall, U., Rode, A. V., Bajt, S., Kuepper, J., Chapman, H. N. 2018; 51: 133–39

  Abstract

  High-resolution Bragg diffraction from aerosolized single granulovirus nanocrystals using an X-ray free-electron laser is demonstrated. The outer dimensions of the in-vacuum aerosol injector components are identical to conventional liquid-microjet nozzles used in serial diffraction experiments, which allows the injector to be utilized with standard mountings. As compared with liquid-jet injection, the X-ray scattering background is reduced by several orders of magnitude by the use of helium carrier gas rather than liquid. Such reduction is required for diffraction measurements of small macromolecular nanocrystals and single particles. High particle speeds are achieved, making the approach suitable for use at upcoming high-repetition-rate facilities.

  View details for PubMedID 29507547

• Determining Orientations of Optical Transition Dipole Moments using Ultrafast X-Ray Scattering. The journal of physical chemistry letters Yong, H. n., Zotev, N. n., Stankus, B. n., Ruddock, J. M., Bellshaw, D. n., Boutet, S. n., Lane, T. J., Liang, M. n., Carbajo, S. n., Robinson, J. S., Du, W. n., Goff, N. n., Chang, Y. n., Koglin, J. E., Waters, M. D., Sølling, T. I., Minitti, M. P., Kirrander, A. n., Weber, P. M. 2018

  Abstract

  The identification of the initially prepared, optically active state remains a challenging problem in many studies of ultrafast photoinduced processes. We show that the initially excited electronic state can be determined using the anisotropic component of ultrafast time-resolved X-ray scattering signals. The concept is demonstrated using the time-dependent X-ray scattering of N-methyl morpholine in the gas-phase upon excitation by a 200 nm linearly polarized optical pulse. Analysis of the angular dependence of the scattering signal near time zero renders the orientation of the transition dipole moment in the molecular frame and identifies the initially excited state as the 3pz Rydberg state, thus bypassing the need for further experimental studies to determine the starting point of the photoinduced dynamics and clarifying inconsistent computational results.

  View details for PubMedID 30380873

• Experimental measurement of material fatigue properties of x-ray optics by using laser pulses Cheng, X., Janowitz, J., Droste, S., Lee, L., Cunningham, E. F., Robinson, J., Fry, A. R., Zhang, L., Carr, C. W., Exarhos, G. J., Gruzdev, V. E., Ristau, D., Soileau, M. J. SPIE-INT SOC OPTICAL ENGINEERING. 2018

  View details for DOI 10.1117/12.2500294

  View details for Web of Science ID 000468660700007

• 4D Pulse Shaping of Discretized Beam Arrays Liu, W., Robinson, J., Fry, A., Carbajo, S., IEEE IEEE. 2018

  View details for Web of Science ID 000526031001321

• Chromophore twisting in the excited state of a photoswitchable fluorescent protein captured by time-resolved serial femtosecond crystallography NATURE CHEMISTRY Coquelle, N., Sliwa, M., Woodhouse, J., Schiro, G., Adam, V., Aquila, A., Barends, T. M., Boutet, S., Byrdin, M., Carbajo, S., De la Mora, E., Doak, R., Feliks, M., Fieschi, F., Foucar, L., Guillon, V., Hilpert, M., Hunter, M. S., Jakobs, S., Koglin, J. E., Kovacsova, G., Lane, T. J., Levy, B., Liang, M., Nass, K., Ridard, J., Robinson, J. S., Roome, C. M., Ruckebusch, C., Seaberg, M., Thepaut, M., Cammarata, M., Demachy, I., Field, M., Shoeman, R. L., Bourgeois, D., Colletier, J., Schlichting, I., Weik, M. 2018; 10 (1): 31–37

  Abstract

  Chromophores absorb light in photosensitive proteins and thereby initiate fundamental biological processes such as photosynthesis, vision and biofluorescence. An important goal in their understanding is the provision of detailed structural descriptions of the ultrafast photochemical events that they undergo, in particular of the excited states that connect chemistry to biological function. Here we report on the structures of two excited states in the reversibly photoswitchable fluorescent protein rsEGFP2. We populated the states through femtosecond illumination of rsEGFP2 in its non-fluorescent off state and observed their build-up (within less than one picosecond) and decay (on the several picosecond timescale). Using an X-ray free-electron laser, we performed picosecond time-resolved crystallography and show that the hydroxybenzylidene imidazolinone chromophore in one of the excited states assumes a near-canonical twisted configuration halfway between the trans and cis isomers. This is in line with excited-state quantum mechanics/molecular mechanics and classical molecular dynamics simulations. Our new understanding of the structure around the twisted chromophore enabled the design of a mutant that displays a twofold increase in its off-to-on photoswitching quantum yield.

  View details for DOI 10.1038/NCHEM.2853

  View details for Web of Science ID 000423143500009

  View details for PubMedID 29256511

• Nonlinear Ultrafast Spin Scattering in the Skyrmion Phase of Cu2OSeO3 PHYSICAL REVIEW LETTERS Langner, M. C., Roy, S., Huang, S. W., Koralek, J. D., Chuang, Y., Dakovski, G. L., Turner, J. J., Robinson, J. S., Coffee, R. N., Minitti, M. P., Seki, S., Tokura, Y., Schoenlein, R. W. 2017; 119 (10): 107204

  Abstract

  Ultrafast x-ray scattering studies of the topological Skyrmion phase in Cu_{2}OSeO_{3} show the dynamics to be strongly dependent on the excitation energy and fluence. At high photon energies, where the electron-spin scattering cross section is relatively high, the excitation of the topological Skyrmion phase shows a nonlinear dependence on the excitation fluence, in contrast to the excitation of the conical phase which is linearly dependent on the excitation fluence. The excitation of the Skyrmion order parameter is nonlinear in the magnetic excitation resulting from scattering during electron-hole recombination, indicating different dominant scattering processes in the conical and Skyrmion phases.

  View details for DOI 10.1103/PhysRevLett.119.107204

  View details for Web of Science ID 000409560100006

  View details for PubMedID 28949160

• From Macrocrystals to Microcrystals: A Strategy for Membrane Protein Serial Crystallography STRUCTURE Dods, R., Bath, P., Arnlund, D., Beyerlein, K. R., Nelson, G., Liang, M., Harimoorthy, R., Berntsen, P., Malmerberg, E., Johansson, L., Andersson, R., Bosman, R., Carbajo, S., Claesson, E., Conrad, C. E., Dahl, P., Hammarin, G., Hunter, M. S., Li, C., Lisova, S., Milathianaki, D., Robinson, J., Safari, C., Sharma, A., Williams, G., Wickstrand, C., Yefanov, O., Davidsson, J., DePonte, D. P., Barty, A., Branden, G., Neutze, R. 2017; 25 (9): 1461-+

  Abstract

  Serial protein crystallography was developed at X-ray free-electron lasers (XFELs) and is now also being applied at storage ring facilities. Robust strategies for the growth and optimization of microcrystals are needed to advance the field. Here we illustrate a generic strategy for recovering high-density homogeneous samples of microcrystals starting from conditions known to yield large (macro) crystals of the photosynthetic reaction center of Blastochloris viridis (RCvir). We first crushed these crystals prior to multiple rounds of microseeding. Each cycle of microseeding facilitated improvements in the RCvir serial femtosecond crystallography (SFX) structure from 3.3-Å to 2.4-Å resolution. This approach may allow known crystallization conditions for other proteins to be adapted to exploit novel scientific opportunities created by serial crystallography.

  View details for PubMedID 28781082

• Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance PHYSICAL REVIEW ACCELERATORS AND BEAMS Li, S., Alverson, S., Bohler, D., Egger, A., Fry, A., Gilevich, S., Huang, Z., Miahnahri, A., Ratner, D., Robinson, J., Zhou, F. 2017; 20 (8)

  View details for DOI 10.1103/PhysRevAccelBeams.20.080704

  View details for Web of Science ID 000407783600001

• Glownia et al. Reply. Physical review letters Glownia, J. M., Natan, A., Cryan, J. P., Hartsock, R., Kozina, M., Minitti, M. P., Nelson, S., Robinson, J., Sato, T., van Driel, T., Welch, G., Weninger, C., Zhu, D., Bucksbaum, P. H. 2017; 119 (6): 069302

  View details for DOI 10.1103/PhysRevLett.119.069302

  View details for PubMedID 28949596

• Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2 '- bipyridine)(2)(CN)(2)] STRUCTURAL DYNAMICS Kjaer, K. S., Zhang, W., Alonso-Mori, R., Bergmann, U., Chollet, M., Hadt, R. G., Hartsock, R. W., Harlang, T., Kroll, T., Kubicek, K., Lemke, H. T., Liang, H. W., Liu, Y., Nielsen, M. M., Robinson, J. S., Solomon, E. I., Sokaras, D., van Driel, T. B., Weng, T., Zhu, D., Persson, P., Warnmark, K., Sundstrom, V., Gaffney, K. J. 2017; 4 (4): 044030

  Abstract

  We have used femtosecond resolution UV-visible and Kβ x-ray emission spectroscopy to characterize the electronic excited state dynamics of [Fe(bpy)2(CN)2], where bpy=2,2'-bipyridine, initiated by metal-to-ligand charge transfer (MLCT) excitation. The excited-state absorption in the transient UV-visible spectra, associated with the 2,2'-bipyridine radical anion, provides a robust marker for the MLCT excited state, while the transient Kβ x-ray emission spectra provide a clear measure of intermediate and high spin metal-centered excited states. From these measurements, we conclude that the MLCT state of [Fe(bpy)2(CN)2] undergoes ultrafast spin crossover to a metal-centered quintet excited state through a short lived metal-centered triplet transient species. These measurements of [Fe(bpy)2(CN)2] complement prior measurement performed on [Fe(bpy)3]2+ and [Fe(bpy)(CN)4]2- in dimethylsulfoxide solution and help complete the chemical series [Fe(bpy)N(CN)6-2N]2N-4, where N = 1-3. The measurements confirm that simple ligand modifications can significantly change the relaxation pathways and excited state lifetimes and support the further investigation of light harvesting and photocatalytic applications of 3d transition metal complexes.

  View details for PubMedID 28653021

• Nonequilibrium lattice-driven dynamics of stripes in nickelates using time-resolved x-ray scattering PHYSICAL REVIEW B Lee, W. S., Kung, Y. F., Moritz, B., Coslovich, G., Kaindl, R. A., Chuang, Y. D., Moore, R. G., Lu, D. H., Kirchmann, P. S., ROBINSON, J. S., Minitti, M. P., Dakovski, G., Schlotter, W. F., Turner, J. J., Gerber, S., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2017; 95 (12)

  View details for DOI 10.1103/PhysRevB.95.121105

  View details for Web of Science ID 000396014600002

• Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution CHEMICAL SCIENCE Zhang, W., Kjaer, K. S., Alonso-Mori, R., Bergmann, U., Chollet, M., Fredin, L. A., Hadt, R. G., Hartsock, R. W., Harlang, T., Kroll, T., Kubicek, K., Lemke, H. T., Liang, H. W., Liu, Y., Nielsen, M. M., Persson, P., Robinson, J. S., Solomon, E. I., Sun, Z., Sokaras, D., van Driel, T. B., Weng, T., Zhu, D., Warnmark, K., Sundstromb, V., Gaffney, K. J. 2017; 8 (1): 515-523

  Abstract

  Developing light-harvesting and photocatalytic molecules made with iron could provide a cost effective, scalable, and environmentally benign path for solar energy conversion. To date these developments have been limited by the sub-picosecond metal-to-ligand charge transfer (MLCT) electronic excited state lifetime of iron based complexes due to spin crossover - the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand iron complexes with four cyanide (CN-) ligands and one 2,2'-bipyridine (bpy) ligand. This enables MLCT excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL) Kβ hard X-ray fluorescence spectroscopy with femtosecond time-resolved UV-visible absorption spectroscopy to characterize the electronic excited state dynamics initiated by MLCT excitation of [Fe(CN)4(bpy)]2-. The two experimental techniques are highly complementary; the time-resolved UV-visible measurement probes allowed electronic transitions between valence states making it sensitive to ligand-centered electronic states such as MLCT states, whereas the Kβ fluorescence spectroscopy provides a sensitive measure of changes in the Fe spin state characteristic of metal-centered excited states. We conclude that the MLCT excited state of [Fe(CN)4(bpy)]2- decays with roughly a 20 ps lifetime without undergoing spin crossover, exceeding the MLCT excited state lifetime of [Fe(2,2'-bipyridine)3]2+ by more than two orders of magnitude.

  View details for DOI 10.1039/c6sc03070j

  View details for Web of Science ID 000391454500060

  View details for PubMedCentralID PMC5341207

• Light-induced picosecond rotational disordering of the inorganic sublattice in hybrid perovskites. Science advances Wu, X. n., Tan, L. Z., Shen, X. n., Hu, T. n., Miyata, K. n., Trinh, M. T., Li, R. n., Coffee, R. n., Liu, S. n., Egger, D. A., Makasyuk, I. n., Zheng, Q. n., Fry, A. n., Robinson, J. S., Smith, M. D., Guzelturk, B. n., Karunadasa, H. I., Wang, X. n., Zhu, X. n., Kronik, L. n., Rappe, A. M., Lindenberg, A. M. 2017; 3 (7): e1602388

  Abstract

  Femtosecond resolution electron scattering techniques are applied to resolve the first atomic-scale steps following absorption of a photon in the prototypical hybrid perovskite methylammonium lead iodide. Following above-gap photoexcitation, we directly resolve the transfer of energy from hot carriers to the lattice by recording changes in the mean square atomic displacements on 10-ps time scales. Measurements of the time-dependent pair distribution function show an unexpected broadening of the iodine-iodine correlation function while preserving the Pb-I distance. This indicates the formation of a rotationally disordered halide octahedral structure developing on picosecond time scales. This work shows the important role of light-induced structural deformations within the inorganic sublattice in elucidating the unique optoelectronic functionality exhibited by hybrid perovskites and provides new understanding of hot carrier-lattice interactions, which fundamentally determine solar cell efficiencies.

  View details for PubMedID 28782016

• Structure of photosystem II and substrate binding at room temperature NATURE Young, I. D., Ibrahim, M., Chatterjee, R., Gul, S., Fuller, F. D., Koroidov, S., Brewster, A. S., Tran, R., Alonso-Mori, R., Kroll, T., Michels-Clark, T., Laksmono, H., Sierra, R. G., Stan, C. A., Hussein, R., Zhang, M., Douthit, L., Kubin, M., de Lichtenberg, C., Long Vo Pham, L. V., Nilsson, H., Cheah, M. H., Shevela, D., Saracini, C., Bean, M. A., Seuffert, I., Sokaras, D., Weng, T., Pastor, E., Weninger, C., Fransson, T., Lassalle, L., Braeuer, P., Aller, P., Docker, P. T., Andi, B., Orville, A. M., Glownia, J. M., Nelson, S., Sikorski, M., Zhu, D., Hunter, M. S., Lane, T. J., Aquila, A., Koglin, J. E., Robinson, J., Liang, M., Boutet, S., Lyubimov, A. Y., Uervirojnangkoorn, M., Moriarty, N. W., Liebschner, D., Afonine, P. V., Waterman, D. G., Evans, G., Wernet, P., Dobbek, H., Weis, W. I., Brunger, A. T., Zwart, P. H., Adams, P. D., Zouni, A., Messinger, J., Bergmann, U., Sauter, N. K., Kern, J., Yachandra, V. K., Yano, J. 2016; 540 (7633): 453-?

  Abstract

  Light-induced oxidation of water by photosystem II (PS II) in plants, algae and cyanobacteria has generated most of the dioxygen in the atmosphere. PS II, a membrane-bound multi-subunit pigment protein complex, couples the one-electron photochemistry at the reaction centre with the four-electron redox chemistry of water oxidation at the Mn4CaO5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S0 to S4), in which S1 is the dark-stable state and S3 is the last semi-stable state before O-O bond formation and O2 evolution. A detailed understanding of the O-O bond formation mechanism remains a challenge, and will require elucidation of both the structures of the OEC in the different S-states and the binding of the two substrate waters to the catalytic site. Here we report the use of femtosecond pulses from an X-ray free electron laser (XFEL) to obtain damage-free, room temperature structures of dark-adapted (S1), two-flash illuminated (2F; S3-enriched), and ammonia-bound two-flash illuminated (2F-NH3; S3-enriched) PS II. Although the recent 1.95 Å resolution structure of PS II at cryogenic temperature using an XFEL provided a damage-free view of the S1 state, measurements at room temperature are required to study the structural landscape of proteins under functional conditions, and also for in situ advancement of the S-states. To investigate the water-binding site(s), ammonia, a water analogue, has been used as a marker, as it binds to the Mn4CaO5 cluster in the S2 and S3 states. Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site. This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O-O bond formation mechanisms.

  View details for DOI 10.1038/nature20161

  View details for Web of Science ID 000389716800046

  View details for PubMedID 27871088

  View details for PubMedCentralID PMC5201176

• Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules PHYSICAL REVIEW LETTERS Yang, J., Guehr, M., Shen, X., Li, R., Vecchione, T., Coffee, R., Corbett, J., Fry, A., Hartmann, N., Hast, C., Hegazy, K., Jobe, K., Makasyuk, I., Robinson, J., Robinson, M. S., Vetter, S., Weathersby, S., Yoneda, C., Wang, X., Centurion, M. 2016; 117 (15)

  Abstract

  Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet.

  View details for DOI 10.1103/PhysRevLett.117.153002

  View details for Web of Science ID 000384479300004

  View details for PubMedID 27768362

• Self-Referenced Coherent Diffraction X-Ray Movie of Angstrom- and Femtosecond-Scale Atomic Motion PHYSICAL REVIEW LETTERS Glownia, J. M., Natan, A., Cryan, J. P., HARTSOCK, R., Kozina, M., Minitti, M. P., Nelson, S., Robinson, J., Sato, T., van Driel, T., Welch, G., WENINGER, C., Zhu, D., Bucksbaum, P. H. 2016; 117 (15)

  Abstract

  Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with a temporal and spatial resolution of 30 fs and 0.3 Å. This high fidelity is due to interference between the nonstationary excitation and the stationary initial charge distribution. The initial state is used as the local oscillator for heterodyne amplification of the excited charge distribution to retrieve real-space movies of atomic motion on ångstrom and femtosecond scales. This x-ray interference has not been employed to image internal motion in molecules before. Coherent vibrational motion and dispersion, dissociation, and rotational dephasing are all clearly visible in the data, thereby demonstrating the stunning sensitivity of heterodyne methods.

  View details for DOI 10.1103/PhysRevLett.117.153003

  View details for Web of Science ID 000384479300005

  View details for PubMedID 27768351

• Liquid explosions induced by X-ray laser pulses NATURE PHYSICS Stan, C. A., Milathianaki, D., Laksmono, H., Sierra, R. G., McQueen, T. A., Messerschmidt, M., Williams, G. J., Koglin, J. E., Lane, T. J., Hayes, M. J., Guillet, S. A., Liang, M., Aquila, A. L., Willmott, P. R., Robinson, J. S., Gumerlock, K. L., Botha, S., Nass, K., Schlichting, I., Shoeman, R. L., Stone, H. A., Boutet, S. 2016; 12 (10): 966-971

  View details for DOI 10.1038/NPHYS3779

  View details for Web of Science ID 000385337700021

• Femtosecond photodissociation dynamics of 1,4-diiodobenzene by gas-phase X-ray scattering and photoelectron spectroscopy. Faraday discussions Stankus, B., Budarz, J. M., Kirrander, A., Rogers, D., Robinson, J., Lane, T. J., Ratner, D., Hastings, J., Minitti, M. P., Weber, P. M. 2016: -?

  Abstract

  We present a multifaceted investigation into the initial photodissociation dynamics of 1,4-diiodobenzene (DIB) following absorption of 267 nm radiation. We combine ultrafast time-resolved photoelectron spectroscopy and X-ray scattering experiments performed at the Linac Coherent Light Source (LCLS) to study the initial electronic excitation and subsequent rotational alignment, and interpret the experiments in light of Complete Active Space Self-Consistent Field (CASSCF) calculations of the excited electronic landscape. The initially excited state is found to be a bound (1)B1 surface, which undergoes ultrafast population transfer to a nearby state in 35 ± 10 fs. The internal conversion most likely leads to one or more singlet repulsive surfaces that initiate the dissociation. This initial study is an essential and prerequisite component of a comprehensive study of the complete photodissociation pathway(s) of DIB at 267 nm. Assignment of the initially excited electronic state as a bound state identifies the mechanism as predissociative, and measurement of its lifetime establishes the time between excitation and initiation of dissociation, which is crucial for direct comparison of photoelectron and scattering experiments.

  View details for PubMedID 27711844

• Negative Pressures and Spallation in Water Drops Subjected to Nanosecond Shock Waves JOURNAL OF PHYSICAL CHEMISTRY LETTERS Stan, C. A., Willmott, P. R., Stone, H. A., Koglin, J. E., Liang, M., Aquila, A. L., Robinson, J. S., Gumerlock, K. L., Blaj, G., Sierra, R. G., Boutet, S., Guillet, S. A., Curtis, R. H., Vetter, S. L., Loos, H., Turner, J. L., Decker, F. 2016; 7 (11): 2055-2062

  Abstract

  Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  View details for DOI 10.1021/acs.jpclett.6b00687

  View details for Web of Science ID 000377239200020

  View details for PubMedID 27182751

• Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4 NATURE MATERIALS Dean, M. M., Cao, Y., Liu, X., Wall, S., Zhu, D., Mankowsky, R., Thampy, V., Chen, X. M., Vale, J. G., Casa, D., Kim, J., Said, A. H., Juhas, P., Alonso-Mori, R., Glownia, J. M., Robert, A., Robinson, J., Sikorski, M., Song, S., Kozina, M., Lemke, H., Patthey, L., Owada, S., Katayama, T., Yabashi, M., Tanaka, Y., Togashi, T., Liu, J., Serrao, C., Kim, B. J., Huber, L., Chang, C., McMorrow, D. F., Foerst, M., Hill, J. P. 2016; 15 (6): 601-+

  Abstract

  Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

  View details for DOI 10.1038/NMAT4641

  View details for Web of Science ID 000376528000009

  View details for PubMedID 27159018

• Diffractive imaging of a rotational wavepacket in nitrogen molecules with femtosecond megaelectronvolt electron pulses NATURE COMMUNICATIONS Yang, J., Guehr, M., Vecchione, T., Robinson, M. S., Li, R., Hartmann, N., Shen, X., Coffee, R., Corbett, J., Fry, A., Gaffney, K., Gorkhover, T., Hast, C., Jobe, K., Makasyuk, I., Reid, A., Robinson, J., Vetter, S., Wang, F., Weathersby, S., Yoneda, C., Centurion, M., Wang, X. 2016; 7

  Abstract

  Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angström spatial precision is one of the critical challenges in the chemical sciences, as the nuclear geometry changes determine the molecular reactivity. For photoexcited molecules, the nuclear dynamics determine the photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where we captured the rotational wavepacket dynamics of nonadiabatically laser-aligned nitrogen molecules. We achieved a combination of 100 fs root-mean-squared temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule. In addition, the diffraction patterns reveal the angular distribution of the molecules, which changes from prolate (aligned) to oblate (anti-aligned) in 300 fs. Our results demonstrate a significant and promising step towards making atomically resolved movies of molecular reactions.

  View details for DOI 10.1038/ncomms11232

  View details for Web of Science ID 000373622400001

  View details for PubMedID 27046298

  View details for PubMedCentralID PMC4822053

• Macromolecular diffractive imaging using imperfect crystals NATURE Ayyer, K., Yefanov, O. M., Oberthuer, D., Roy-Chowdhury, S., Galli, L., Mariani, V., Basu, S., Coe, J., Conrad, C. E., Fromme, R., Schaffer, A., Droener, K., James, D., Kupitz, C., Metz, M., Nelson, G., Xavier, P., Beyerlein, K. R., Schmidt, M., Sarrou, I., Spence, J. H., Weierstall, U., White, T. A., Yang, J., Zhao, Y., Liang, M., Aquila, A., Hunter, M. S., Robinson, J. S., Koglin, J. E., Boutet, S., Fromme, P., Barty, A., Chapman, H. N. 2016; 530 (7589): 202-+

  Abstract

  The three-dimensional structures of macromolecules and their complexes are mainly elucidated by X-ray protein crystallography. A major limitation of this method is access to high-quality crystals, which is necessary to ensure X-ray diffraction extends to sufficiently large scattering angles and hence yields information of sufficiently high resolution with which to solve the crystal structure. The observation that crystals with reduced unit-cell volumes and tighter macromolecular packing often produce higher-resolution Bragg peaks suggests that crystallographic resolution for some macromolecules may be limited not by their heterogeneity, but by a deviation of strict positional ordering of the crystalline lattice. Such displacements of molecules from the ideal lattice give rise to a continuous diffraction pattern that is equal to the incoherent sum of diffraction from rigid individual molecular complexes aligned along several discrete crystallographic orientations and that, consequently, contains more information than Bragg peaks alone. Although such continuous diffraction patterns have long been observed--and are of interest as a source of information about the dynamics of proteins--they have not been used for structure determination. Here we show for crystals of the integral membrane protein complex photosystem II that lattice disorder increases the information content and the resolution of the diffraction pattern well beyond the 4.5-ångström limit of measurable Bragg peaks, which allows us to phase the pattern directly. Using the molecular envelope conventionally determined at 4.5 ångströms as a constraint, we obtain a static image of the photosystem II dimer at a resolution of 3.5 ångströms. This result shows that continuous diffraction can be used to overcome what have long been supposed to be the resolution limits of macromolecular crystallography, using a method that exploits commonly encountered imperfect crystals and enables model-free phasing.

  View details for PubMedID 26863980

  View details for PubMedCentralID PMC4839592

• Femtosecond gas phase electron diffraction with MeV electrons FARADAY DISCUSSIONS Yang, J., Guehr, M., Vecchione, T., Robinson, M. S., Li, R., Hartmann, N., Shen, X., Coffee, R., Corbett, J., Fry, A., Gaffney, K., Gorkhover, T., Hast, C., Jobe, K., Makasyuk, I., Reid, A., Robinson, J., Vetter, S., Wang, F., Weathersby, S., Yoneda, C., Wang, X., Centurion, M. 2016; 194: 563–81

  Abstract

  We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution.

  View details for DOI 10.1039/c6fd00071a

  View details for Web of Science ID 000392422200026

  View details for PubMedID 27711826

• Ultrafast x-ray and optical signatures of phase competition and separation underlying the photoinduced metallic phase in Pr1-xCaxMnO3 PHYSICAL REVIEW B Langner, M. C., Zhou, S., Coslovich, G., Chuang, Y., Zhu, Y., ROBINSON, J. S., Schlotter, W. F., Turner, J. J., Minitti, M. P., Moore, R. G., Lee, W. S., Lu, D. H., Doering, D., Denes, P., Tomioka, Y., Tokura, Y., Kaindl, R. A., Schoenlein, R. W. 2015; 92 (15)

  View details for DOI 10.1103/PhysRevB.92.155148

  View details for Web of Science ID 000363790400002

• Strongly aligned gas-phase molecules at free-electron lasers JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Kierspel, T., Wiese, J., Mullins, T., Robinson, J., Aquila, A., Barty, A., Bean, R., Boll, R., Boutet, S., Bucksbaum, P., Chapman, H. N., Christensen, L., Fry, A., Hunter, M., Koglin, J. E., Liang, M., Mariani, V., Morgan, A., Natan, A., Petrovic, V., Rolles, D., Rudenko, A., Schnorr, K., Stapelfeldt, H., Stern, S., Thogersen, J., Yoon, C. H., Wang, F., Trippel, S., Kuepper, J. 2015; 48 (20)

  View details for DOI 10.1088/0953-4075/48/20/204002

  View details for Web of Science ID 000362421800004

• Spatially resolved ultrafast magnetic dynamics initiated at a complex oxide heterointerface NATURE MATERIALS Foerst, M., Caviglia, A. D., Scherwitzl, R., MANKOWSKY, R., Zubko, P., Khanna, V., Bromberger, H., Wilkins, S. B., Chuang, Y., Lee, W. S., Schlotter, W. F., Turner, J. J., Dakovski, G. L., Minitti, M. P., Robinson, J., Clark, S. R., Jaksch, D., Triscone, J., Hill, J. P., Dhesi, S. S., Cavalleri, A. 2015; 14 (9): 883-?

  Abstract

  Static strain in complex oxide heterostructures has been extensively used to engineer electronic and magnetic properties at equilibrium. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across heterointerfaces dynamically. Here, by exciting large-amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a heterointerface. Femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering. We observe a magnetic melt front that propagates from the substrate interface into the film, at a speed that suggests electronically driven motion. Light control and ultrafast phase front propagation at heterointerfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices.

  View details for DOI 10.1038/NMAT4341

  View details for Web of Science ID 000360192000019

  View details for PubMedID 26147844

• Imaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reaction PHYSICAL REVIEW LETTERS Minitti, M. P., Budarz, J. M., Kirrander, A., ROBINSON, J. S., Ratner, D., Lane, T. J., Zhu, D., Glownia, J. M., Kozina, M., Lemke, H. T., Sikorski, M., Feng, Y., Nelson, S., Saita, K., Stankus, B., Northey, T., Hastings, J. B., Weber, P. M. 2015; 114 (25)

  Abstract

  Structural rearrangements within single molecules occur on ultrafast time scales. Many aspects of molecular dynamics, such as the energy flow through excited states, have been studied using spectroscopic techniques, yet the goal to watch molecules evolve their geometrical structure in real time remains challenging. By mapping nuclear motions using femtosecond x-ray pulses, we have created real-space representations of the evolving dynamics during a well-known chemical reaction and show a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-ray scattering. A computational analysis optimally matches the series of scattering patterns produced by the x rays to a multitude of potential reaction paths. In so doing, we have made a critical step toward the goal of viewing chemical reactions on femtosecond time scales, opening a new direction in studies of ultrafast chemical reactions in the gas phase.

  View details for DOI 10.1103/PhysRevLett.114.255501

  View details for Web of Science ID 000356586100002

  View details for PubMedID 26197134

• Bright high-repetition-rate source of narrowband extreme-ultraviolet harmonics beyond 22 eV NATURE COMMUNICATIONS Wang, H., Xu, Y., Ulonska, S., Robinson, J. S., Ranitovic, P., Kaindl, R. A. 2015; 6: 7459

  Abstract

  Novel table-top sources of extreme-ultraviolet light based on high-harmonic generation yield unique insight into the fundamental properties of molecules, nanomaterials or correlated solids, and enable advanced applications in imaging or metrology. Extending high-harmonic generation to high repetition rates portends great experimental benefits, yet efficient extreme-ultraviolet conversion of correspondingly weak driving pulses is challenging. Here, we demonstrate a highly-efficient source of femtosecond extreme-ultraviolet pulses at 50-kHz repetition rate, utilizing the ultraviolet second-harmonic focused tightly into Kr gas. In this cascaded scheme, a photon flux beyond ≈3 × 10(13) s(-1) is generated at 22.3 eV, with 5 × 10(-5) conversion efficiency that surpasses similar harmonics directly driven by the fundamental by two orders-of-magnitude. The enhancement arises from both wavelength scaling of the atomic dipole and improved spatio-temporal phase matching, confirmed by simulations. Spectral isolation of a single 72-meV-wide harmonic renders this bright, 50-kHz extreme-ultraviolet source a powerful tool for ultrafast photoemission, nanoscale imaging and other applications.

  View details for DOI 10.1038/ncomms8459

  View details for Web of Science ID 000357177400003

  View details for PubMedID 26067922

  View details for PubMedCentralID PMC4490359

• Optical laser systems at the Linac Coherent Light Source JOURNAL OF SYNCHROTRON RADIATION Minitti, M. P., Robinson, J. S., Coffee, R. N., Edstrom, S., Gilevich, S., Glownia, J. M., Granados, E., Hering, P., Hoffmann, M. C., Miahnahri, A., Milathianaki, D., Polzin, W., Ratner, D., Tavella, F., Vetter, S., Welch, M., White, W. E., Fry, A. R. 2015; 22: 526–31

  Abstract

  Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently commissioned X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS). Pump-probe experimental techniques reveal ultrafast dynamics in atomic and molecular processes and reveal new insights in chemistry, biology, material science and high-energy-density physics. This manuscript describes the laser systems and experimental methods that enable cutting-edge optical laser/X-ray pump-probe experiments to be performed at LCLS.

  View details for PubMedID 25931064

  View details for PubMedCentralID PMC4416671

• Nonlinear delayed symmetry breaking in a solid excited by hard x-ray free electron laser pulses APPLIED PHYSICS LETTERS Ferrer, A., Johnson, J. A., Huber, T., Mariager, S. O., Trant, M., Gruebel, S., Zhu, D., Chollet, M., Robinson, J., Lemke, H. T., Ingold, G., Milne, C., Staub, U., Beaud, P., Johnson, S. L. 2015; 106 (15)

  View details for DOI 10.1063/1.4917506

  View details for Web of Science ID 000353160700049

• Visualization of nanocrystal breathing modes at extreme strains NATURE COMMUNICATIONS Szilagyi, E., Wittenberg, J. S., Miller, T. A., Lutker, K., Quirin, F., Lemke, H., Zhu, D., Chollet, M., Robinson, J., Wen, H., Sokolowski-Tinten, K., Lindenberg, A. M. 2015; 6

  Abstract

  Nanoscale dimensions in materials lead to unique electronic and structural properties with applications ranging from site-specific drug delivery to anodes for lithium-ion batteries. These functional properties often involve large-amplitude strains and structural modifications, and thus require an understanding of the dynamics of these processes. Here we use femtosecond X-ray scattering techniques to visualize, in real time and with atomic-scale resolution, light-induced anisotropic strains in nanocrystal spheres and rods. Strains at the percent level are observed in CdS and CdSe samples, associated with a rapid expansion followed by contraction along the nanosphere or nanorod radial direction driven by a transient carrier-induced stress. These morphological changes occur simultaneously with the first steps in the melting transition on hundreds of femtosecond timescales. This work represents the first direct real-time probe of the dynamics of these large-amplitude strains and shape changes in few-nanometre-scale particles.

  View details for DOI 10.1038/ncomms7577

  View details for Web of Science ID 000352720700012

  View details for PubMedID 25762350

• Irreversible transformation of ferromagnetic ordered stripe domains in single-shot infrared-pump/resonant-x-ray-scattering-probe experiments PHYSICAL REVIEW B Bergeard, N., Schaffert, S., Lopez-Flores, V., Jaouen, N., Geilhufe, J., Guenther, C. M., Schneider, M., Graves, C., Wang, T., Wu, B., Scherz, A., Baumier, C., Delaunay, R., Fortuna, F., Tortarolo, M., Tudu, B., Krupin, O., Minitti, M. P., Robinson, J., Schlotter, W. F., Turner, J. J., Luening, J., Eisebitt, S., Boeglin, C. 2015; 91 (5)

  View details for DOI 10.1103/PhysRevB.91.054416

  View details for Web of Science ID 000351770800003

• Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa₂Cu₃O_6.5 NATURE Mankowsky, R., Subedi, A., Foerst, M., Mariager, S. O., Chollet, M., Lemke, H. T., Robinson, J. S., Glownia, J. M., Minitti, M. P., Frano, A., Fechner, M., Spaldin, N. A., Loew, T., Keimer, B., Georges, A., Cavalleri, A. 2014; 516 (7529): 71-73

  Abstract

  Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures. In complex oxides, this method has been used to melt electronic order, drive insulator-to-metal transitions and induce superconductivity. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+x (refs 9, 10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-O2 intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O-Cu-O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the character of the in-plane electronic structure is likely to favour superconductivity.

  View details for DOI 10.1038/nature13875

  View details for Web of Science ID 000346310800040

  View details for PubMedID 25471882

• Femtosecond x rays link melting of charge-density wave correlations and light-enhanced coherent transport in YBa₂Cu₃O_6.6 PHYSICAL REVIEW B Foerst, M., Frano, A., Kaiser, S., Mankowsky, R., Hunt, C. R., Turner, J. J., Dakovski, G. L., Minitti, M. P., Robinson, J., Loew, T., Le Tacon, M., Keimer, B., Hill, J. P., Cavalleri, A., Dhesi, S. S. 2014; 90 (18)

  View details for DOI 10.1103/PhysRevB.90.184514

  View details for Web of Science ID 000345640600007

• Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources REVIEW OF SCIENTIFIC INSTRUMENTS Shavorskiy, A., Neppl, S., Slaughter, D. S., Cryan, J. P., Siefermann, K. R., Weise, F., Lin, M., Bacellar, C., Ziemkiewicz, M. P., Zegkinoglou, I., Fraund, M. W., Khurmi, C., Hertlein, M. P., Wright, T. W., Huse, N., Schoenlein, R. W., Tyliszczak, T., Coslovich, G., Robinson, J., Kaindl, R. A., Rude, B. S., Oelsner, A., Maehl, S., Bluhm, H., Gessner, O. 2014; 85 (9): 093102

  Abstract

  An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with the retarding ratio can be well approximated by applying Liouville's theorem of constant emittance to the electron trajectories inside the lens system. The performance of the setup is demonstrated by characterizing the laser fluence-dependent transient surface photovoltage response of a laser-excited Si(100) sample.

  View details for PubMedID 25273702

• Atomic-Scale Perspective of Ultrafast Charge Transfer at a Dye-Semiconductor Interface JOURNAL OF PHYSICAL CHEMISTRY LETTERS Siefermann, K. R., Pemmaraju, C. D., Neppl, S., Shavorskiy, A., Cordones, A. A., Vura-Weis, J., Slaughter, D. S., Sturm, F. P., Weise, F., Bluhm, H., Strader, M. L., Cho, H., Lin, M., Bacellar, C., Khurmi, C., Guo, J., Coslovich, G., Robinson, J. S., Kaindl, R. A., Schoenlein, R. W., Belkacem, A., Neumark, D. M., Leone, S. R., Nordlund, D., Ogasawara, H., Krupin, O., Turner, J. J., Schlotter, W. F., Holmes, M. R., Messerschmidt, M., Minitti, M. P., Gul, S., Zhang, J. Z., Huse, N., Prendergast, D., Gessner, O. 2014; 5 (15): 2753-2759

  Abstract

  Understanding interfacial charge-transfer processes on the atomic level is crucial to support the rational design of energy-challenge relevant systems such as solar cells, batteries, and photocatalysts. A femtosecond time-resolved core-level photoelectron spectroscopy study is performed that probes the electronic structure of the interface between ruthenium-based N3 dye molecules and ZnO nanocrystals within the first picosecond after photoexcitation and from the unique perspective of the Ru reporter atom at the center of the dye. A transient chemical shift of the Ru 3d inner-shell photolines by (2.3 ± 0.2) eV to higher binding energies is observed 500 fs after photoexcitation of the dye. The experimental results are interpreted with the aid of ab initio calculations using constrained density functional theory. Strong indications for the formation of an interfacial charge-transfer state are presented, providing direct insight into a transient electronic configuration that may limit the efficiency of photoinduced free charge-carrier generation.

  View details for DOI 10.1021/jz501264x

  View details for Web of Science ID 000340222200044

  View details for PubMedID 26277975

• Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature Zhang, W., Alonso-Mori, R., Bergmann, U., Bressler, C., Chollet, M., Galler, A., Gawelda, W., Hadt, R. G., Hartsock, R. W., Kroll, T., Kjær, K. S., Kubicek, K., Lemke, H. T., Liang, H. W., Meyer, D. A., Nielsen, M. M., Purser, C., Robinson, J. S., Solomon, E. I., Sun, Z., Sokaras, D., van Driel, T. B., Vankó, G., Weng, T., Zhu, D., Gaffney, K. J. 2014; 509 (7500): 345-348

  Abstract

  Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons. But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics and the flux limitations of ultrafast X-ray sources. Such a situation exists for archetypal polypyridyl iron complexes, such as [Fe(2,2'-bipyridine)3](2+), where the excited-state charge and spin dynamics involved in the transition from a low- to a high-spin state (spin crossover) have long been a source of interest and controversy. Here we demonstrate that femtosecond resolution X-ray fluorescence spectroscopy, with its sensitivity to spin state, can elucidate the spin crossover dynamics of [Fe(2,2'-bipyridine)3](2+) on photoinduced metal-to-ligand charge transfer excitation. We are able to track the charge and spin dynamics, and establish the critical role of intermediate spin states in the crossover mechanism. We anticipate that these capabilities will make our method a valuable tool for mapping in unprecedented detail the fundamental electronic excited-state dynamics that underpin many useful light-triggered molecular phenomena involving 3d transition metal complexes.

  View details for DOI 10.1038/nature13252

  View details for PubMedID 24805234

• Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature Zhang, W., Alonso-Mori, R., Bergmann, U., Bressler, C., Chollet, M., Galler, A., Gawelda, W., Hadt, R. G., Hartsock, R. W., Kroll, T., Kjær, K. S., Kubicek, K., Lemke, H. T., Liang, H. W., Meyer, D. A., Nielsen, M. M., Purser, C., Robinson, J. S., Solomon, E. I., Sun, Z., Sokaras, D., van Driel, T. B., Vankó, G., Weng, T., Zhu, D., Gaffney, K. J. 2014; 509 (7500): 345-348

  Abstract

  Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons. But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics and the flux limitations of ultrafast X-ray sources. Such a situation exists for archetypal polypyridyl iron complexes, such as [Fe(2,2'-bipyridine)3](2+), where the excited-state charge and spin dynamics involved in the transition from a low- to a high-spin state (spin crossover) have long been a source of interest and controversy. Here we demonstrate that femtosecond resolution X-ray fluorescence spectroscopy, with its sensitivity to spin state, can elucidate the spin crossover dynamics of [Fe(2,2'-bipyridine)3](2+) on photoinduced metal-to-ligand charge transfer excitation. We are able to track the charge and spin dynamics, and establish the critical role of intermediate spin states in the crossover mechanism. We anticipate that these capabilities will make our method a valuable tool for mapping in unprecedented detail the fundamental electronic excited-state dynamics that underpin many useful light-triggered molecular phenomena involving 3d transition metal complexes.

  View details for DOI 10.1038/nature13252

  View details for PubMedID 24805234

• Real-time visualization of nanocrystal solid-solid transformation pathways. Nano letters Wittenberg, J. S., Miller, T. A., Szilagyi, E., Lutker, K., Quirin, F., Lu, W., Lemke, H., Zhu, D., Chollet, M., Robinson, J., Wen, H., Sokolowski-Tinten, K., Alivisatos, A. P., Lindenberg, A. M. 2014; 14 (4): 1995-1999

  Abstract

  Measurement and understanding of the microscopic pathways materials follow as they transform is crucial for the design and synthesis of new metastable phases of matter. Here we employ femtosecond single-shot X-ray diffraction techniques to measure the pathways underlying solid-solid phase transitions in cadmium sulfide nanorods, a model system for a general class of martensitic transformations. Using picosecond rise-time laser-generated shocks to trigger the transformation, we directly observe the transition state dynamics associated with the wurtzite-to-rocksalt structural phase transformation in cadmium sulfide with atomic-scale resolution. A stress-dependent transition path is observed. At high peak stresses, the majority of the sample is converted directly into the rocksalt phase with no evidence of an intermediate prior to rocksalt formation. At lower peak stresses, a transient five-coordinated intermediate structure is observed consistent with previous first principles modeling.

  View details for DOI 10.1021/nl500043c

  View details for PubMedID 24588125

• Toward structural femtosecond chemical dynamics: imaging chemistry in space and time FARADAY DISCUSSIONS Minitti, M. P., Budarz, J. M., Kirrander, A., Robinson, J., Lane, T. J., Ratner, D., Saita, K., Northey, T., Stankus, B., Cofer-Shabica, V., Hastings, J., Weber, P. M. 2014; 171: 81-91

  Abstract

  We aim to observe a chemical reaction in real time using gas-phase X-ray diffraction. In our initial experiment at the Linac Coherent Light Source (LCLS), we investigated the model system 1,3-cyclohexadiene (CHD) at very low vapor pressures. This reaction serves as a benchmark for numerous transformations in organic synthesis and natural product biology. Excitation of CHD by an ultraviolet optical pulse initiates an electrocyclic reaction that transforms the closed ring system into the open-chain structure of 1,3,5-hexatriene. We describe technical points of the experimental method and present first results. We also outline an approach to analyze the data involving nonlinear least-square optimization routines that match the experimental observations with predicted diffraction patterns calculated from trajectories for nonadiabatic vibronic wave packets.

  View details for DOI 10.1039/c4fd00030g

  View details for Web of Science ID 000345529900004

  View details for PubMedID 25415842

• Photoinduced melting of magnetic order in the correlated electron insulator NdNiO3 PHYSICAL REVIEW B Caviglia, A. D., Foerst, M., Scherwitzl, R., Khanna, V., Bromberger, H., MANKOWSKY, R., Singla, R., Chuang, Y., Lee, W. S., Krupin, O., Schlotter, W. F., Turner, J. J., Dakovski, G. L., Minitti, M. P., Robinson, J., Scagnoli, V., Wilkins, S. B., Cavill, S. A., Gibert, M., Gariglio, S., Zubko, P., Triscone, J., Hill, J. P., Dhesi, S. S., Cavalleri, A. 2013; 88 (22)

  View details for DOI 10.1103/PhysRevB.88.220401

  View details for Web of Science ID 000328570200001

• Femtosecond Visualization of Lattice Dynamics in Shock-Compressed Matter SCIENCE Milathianaki, D., Boutet, S., Williams, G. J., Higginbotham, A., Ratner, D., Gleason, A. E., Messerschmidt, M., Seibert, M. M., Swift, D. C., Hering, P., Robinson, J., White, W. E., Wark, J. S. 2013; 342 (6155): 220-223

  Abstract

  The ultrafast evolution of microstructure is key to understanding high-pressure and strain-rate phenomena. However, the visualization of lattice dynamics at scales commensurate with those of atomistic simulations has been challenging. Here, we report femtosecond x-ray diffraction measurements unveiling the response of copper to laser shock-compression at peak normal elastic stresses of ~73 gigapascals (GPa) and strain rates of 10(9) per second. We capture the evolution of the lattice from a one-dimensional (1D) elastic to a 3D plastically relaxed state within a few tens of picoseconds, after reaching shear stresses of 18 GPa. Our in situ high-precision measurement of material strength at spatial (<1 micrometer) and temporal (<50 picoseconds) scales provides a direct comparison with multimillion-atom molecular dynamics simulations.

  View details for DOI 10.1126/science.1239566

  View details for Web of Science ID 000325475200038

  View details for PubMedID 24115435

• Real-Time Manifestation of Strongly Coupled Spin and Charge Order Parameters in Stripe-Ordered La1.75Sr0.25NiO4 Nickelate Crystals Using Time-Resolved Resonant X-Ray Diffraction PHYSICAL REVIEW LETTERS Chuang, Y. D., Lee, W. S., Kung, Y. F., Sorini, A. P., Moritz, B., Moore, R. G., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Yi, M., Krupin, O., Langner, M., Zhu, Y., Zhou, S. Y., Reis, D. A., Huse, N., ROBINSON, J. S., Kaindl, R. A., Schoenlein, R. W., Johnson, S. L., Foerst, M., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2013; 110 (12)

  Abstract

  We investigate the order parameter dynamics of the stripe-ordered nickelate, La_{1.75}Sr_{0.25}NiO_{4}, using time-resolved resonant x-ray diffraction. In spite of distinct spin and charge energy scales, the two order parameters' amplitude dynamics are found to be linked together due to strong coupling. Additionally, the vector nature of the spin sector introduces a longer reorientation time scale which is absent in the charge sector. These findings demonstrate that the correlation linking the symmetry-broken states does not unbind during the nonequilibrium process, and the time scales are not necessarily associated with the characteristic energy scales of individual degrees of freedom.

  View details for DOI 10.1103/PhysRevLett.110.127404

  View details for Web of Science ID 000316411100019

• Surface plasmon assisted electron acceleration in photoemission from gold nanopillars CHEMICAL PHYSICS Nagel, P. M., Robinson, J. S., Harteneck, B. D., Pfeifer, T., Abel, M. J., Prell, J. S., Neumark, D. M., Kaindl, R. A., Leone, S. R. 2013; 414: 106-111

  View details for DOI 10.1016/j.chemphys.2012.03.013

  View details for Web of Science ID 000315818700015

• Time-Resolved X-Ray Photoelectron Spectroscopy Techniques For Real-Time Studies Of Interfacial Charge Transfer Dynamics 22nd International Conference on the Application of Accelerators in Research and Industry (CAARI) Shavorskiy, A., Cordones, A., Vura-Weis, J., Siefermann, K., Slaughter, D., Sturm, F., Weise, F., Bluhm, H., Strader, M., Cho, H., Lin, M., Bacellar, C., Khurmi, C., Hertlein, M., Guo, J., Tyliszczak, T., Prendergast, D., Coslovich, G., Robinson, J., Kaindl, R. A., Schoenlein, R. W., Belkacem, A., Weber, T., Neumark, D. M., Leone, S. R., Nordlund, D., Ogasawara, H., Nilsson, A. R., Krupin, O., Turner, J. J., Schlotter, W. F., Holmes, M. R., Heimann, P. A., Messerschmidt, M., Minitti, M. P., Beye, M., Gul, S., Zhang, J. Z., Huse, N., Gessner, O. AMER INST PHYSICS. 2013: 475–479

  View details for DOI 10.1063/1.4802374

  View details for Web of Science ID 000319997900095

• Femtosecond optical/hard x-ray timing diagnostics at an FEL: Implementation and Performance Lemke, H. T., Weaver, M., Chollet, M., Robinson, J., Glownia, J. M., Zhu, D., Bionta, M. R., Cammarata, M., Harmand, M., Coffee, R. N., Fritz, D. M., Tschentscher, T., Tiedtke, K. SPIE-INT SOC OPTICAL ENGINEERING. 2013

  View details for DOI 10.1117/12.2017603

  View details for Web of Science ID 000323547400012

• Recent development of thin diamond crystals for X-ray FEL beam-sharing Conference on Advances in X-ray Free-Electron Lasers II - Instrumentation Feng, Y., Alonso-Mori, R., Blank, V., Boutet, S., Chollet, M., van Driel, T. B., Fritz, D. M., Glownia, J. M., Hastings, J. B., Lemke, H., Messerchmidt, M., Montanez, P. A., Robert, A., Robinson, J., Samoylova, L., Shvyd'ko, Y., Sikorski, M., Sinn, H., Song, S., Srinivasan, V. N., Stoupin, S., Terentiev, S., Williams, G., Zhu, D. SPIE-INT SOC OPTICAL ENGINEERING. 2013

  View details for DOI 10.1117/12.1518467

  View details for Web of Science ID 000323547400004

• Invited Review Article: Technology for Attosecond Science REVIEW OF SCIENTIFIC INSTRUMENTS Frank, F., Arrell, C., Witting, T., Okell, W. A., McKenna, J., Robinson, J. S., Haworth, C. A., Austin, D., Teng, H., Walmsley, I. A., Marangos, J. P., Tisch, J. G. 2012; 83 (7): 071101

  Abstract

  We describe a complete technological system at Imperial College London for Attosecond Science studies. The system comprises a few-cycle, carrier envelope phase stabilized laser source which delivers sub 4 fs pulses to a vibration-isolated attosecond vacuum beamline. The beamline is used for the generation of isolated attosecond pulses in the extreme ultraviolet (XUV) at kilohertz repetition rates through laser-driven high harmonic generation in gas targets. The beamline incorporates: interferometers for producing pulse sequences for pump-probe studies; the facility to spectrally and spatially filter the harmonic radiation; an in-line spatially resolving XUV spectrometer; and a photoelectron spectroscopy chamber in which attosecond streaking is used to characterize the attosecond pulses. We discuss the technology and techniques behind the development of our complete system and summarize its performance. This versatile apparatus has enabled a number of new experimental investigations which we briefly describe.

  View details for DOI 10.1063/1.4731658

  View details for Web of Science ID 000307527900001

  View details for PubMedID 22852664

• Phase fluctuations and the absence of topological defects in a photo-excited charge-ordered nickelate NATURE COMMUNICATIONS Lee, W. S., Chuang, Y. D., Moore, R. G., Zhu, Y., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Krupin, O., Yi, M., Langner, M., Huse, N., ROBINSON, J. S., Chen, Y., Zhou, S. Y., Coslovich, G., Huber, B., Reis, D. A., Kaindl, R. A., Schoenlein, R. W., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Johnson, S. L., Foerst, M., Sasagawa, T., Kung, Y. F., Sorini, A. P., Kemper, A. F., Moritz, B., Devereaux, T. P., Lee, D., Shen, Z. X., Hussain, Z. 2012; 3

  Abstract

  The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La(1.75)Sr(0.25)NiO(4) to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter.

  View details for DOI 10.1038/ncomms1837

  View details for Web of Science ID 000304611400033

  View details for PubMedID 22588300

• Plasmon-assisted Photoemission from Gold Nanopillars in Few-cycle Laser Fields Robinson, J. S., Nagel, P. M., Harteneck, B. D., Abel, M. J., Prell, J. S., Neumark, D. M., Pfeifer, T., Leone, S. R., Kaindl, R. A., IEEE IEEE. 2012

  View details for Web of Science ID 000310362403197

• Frequency-tuned isolated attosecond pulses characterized by both 750 nm and 400 nm wavelength streak fields Mashiko, H., Bell, M., Beck, A. R., Abel, M. J., Nagel, P. M., Steiner, C. P., Robinson, J., Siefermann, K. R., Neumark, D. M., Leone, S. R., IEEE IEEE. 2011

  View details for Web of Science ID 000295612403325

• Tunable frequency-controlled isolated attosecond pulses characterized by either 750 nm or 400 nm wavelength streak fields OPTICS EXPRESS Mashiko, H., Bell, M., Beck, A. R., Abel, M. J., Nagel, P. M., Steiner, C. P., Robinson, J., Neumark, D. M., Leone, S. R. 2010; 18 (25): 25887-25895

  Abstract

  A compact and robust Mach-Zehnder type interferometer coupled with the double optical gating technique provides tunable isolated attosecond pulses and streak field detection with fields centered at either 750 nm or 400 nm. Isolated attosecond pulses produced at 45 eV (with measured pulse duration of 114 ± 4 as) and 20 eV (with measured pulse duration of 395 ± 6 as) are temporally characterized with a 750 nm wavelength streak field. In addition, an isolated 118 ± 10 as pulse at 45 eV is measured with a 400 nm wavelength streak field. The interferometer design used herein provides broad flexibility for attosecond streak experiments, allowing pump and probe pulses to be specified independently. This capability is important for studying selected electronic transitions in atoms and molecules.

  View details for DOI 10.1364/OE.18.025887

  View details for Web of Science ID 000285749500042

  View details for PubMedID 21164934

• The generation and utilization of half-cycle cut-offs in high harmonic spectra LASER & PHOTONICS REVIEWS Chipperfield, L. E., Robinson, J. S., Knight, P. L., Marangos, J. P., Tisch, J. G. 2010; 4 (6): 697-719

  View details for DOI 10.1002/lpor.200900028

  View details for Web of Science ID 000284017900002

• High harmonic generation in a gas-filled hollow-core photonic crystal fiber APPLIED PHYSICS B-LASERS AND OPTICS Heckl, O. H., Baer, C. E., Kraenkel, C., Marchese, S. V., Schapper, F., Holler, M., Suedmeyer, T., Robinson, J. S., Tisch, J. G., Couny, F., Light, P., Benabid, F., Keller, U. 2009; 97 (2): 369-373

  View details for DOI 10.1007/s00340-009-3771-x

  View details for Web of Science ID 000271089300016

• Ideal Waveform to Generate the Maximum Possible Electron Recollision Energy for Any Given Oscillation Period PHYSICAL REVIEW LETTERS Chipperfield, L. E., Robinson, J. S., Tisch, J. G., Marangos, J. P. 2009; 102 (6): 063003

  Abstract

  We present the perfect waveform which, during a strong field interaction, generates the maximum possible electron recollision energy for any given oscillation period, over 3 times as high as that for a pure sinusoidal wave. This ideal waveform has the form of a linear ramp with a dc offset. A genetic algorithm was employed to find an optimized practically achievable waveform composed of a longer wavelength field, to provide the offset, in addition to higher frequency components. This second waveform is found to be capable of generating electron recollision energies as high as those for the perfect waveform while retaining the high recollision amplitudes of a pure sinusoidal wave. Calculations of high harmonic generation demonstrate this enhancement, by increasing the cutoff energy by a factor of 2.5 while maintaining the harmonic yield, providing an enhanced tool for attosecond science.

  View details for DOI 10.1103/PhysRevLett.102.063003

  View details for Web of Science ID 000263389500018

  View details for PubMedID 19257585

• First Demonstration of High Harmonic Generation (HHG) in a Hollow-Core Photonic Crystal Fiber Heckl, O. H., Baer, C. E., Kraenkel, C., Marchese, S. V., Schapper, F., Holler, M., Suedmeyer, T., Keller, U., Robinson, J. S., Tisch, J. G., Couny, F., Light, P., Enabid, F., Russell, P. J., IEEE IEEE. 2009: 2703-+

  View details for Web of Science ID 000274751302336

• Laser heating of large noble gas clusters: from the resonant to the relativistic interaction regimes NEW JOURNAL OF PHYSICS Gumbrell, E. T., Moore, A. S., Lazarus, J. A., Clark, E. L., Nilson, P. M., Garbett, W. J., Comley, A. J., Robinson, J. S., Hohenberger, M., Edwards, R. D., Eagleton, R. E., Clarke, R. J., Symes, D. R., Smith, R. A. 2008; 10

  View details for DOI 10.1088/1367-2630/10/12/123011

  View details for Web of Science ID 000261469800006

• Dynamic two-center interference in high-order harmonic generation from molecules with attosecond nuclear motion PHYSICAL REVIEW LETTERS Baker, S., Robinson, J. S., Lein, M., Chirila, C. C., Torres, R., Bandulet, H. C., Comtois, D., Kieffer, J. C., Villeneuve, D. M., Tisch, J. G., Marangos, J. P. 2008; 101 (5): 053901

  Abstract

  We report a new dynamic two-center interference effect in high-harmonic generation from H2, in which the attosecond nuclear motion of H2+ initiated at ionization causes interference to be observed at lower harmonic orders than would be the case for static nuclei. To enable this measurement we utilize a recently developed technique for probing the attosecond nuclear dynamics of small molecules. The experimental results are reproduced by a theoretical analysis based upon the strong-field approximation which incorporates the temporally dependent two-center interference term.

  View details for DOI 10.1103/PhysRevLett.101.053901

  View details for Web of Science ID 000258384700019

  View details for PubMedID 18764392

• Measurement of electronic structure from high harmonic generation in non-adiabatically aligned polyatomic molecules NEW JOURNAL OF PHYSICS Kajumba, N., Torres, R., Underwood, J. G., Robinson, J. S., Baker, S., Tisch, J. G., de Nalda, R., Bryan, W. A., Velotta, R., Altucci, C., Procino, I., Turcu, I. E., Marangos, J. P. 2008; 10

  View details for DOI 10.1088/1367-2630/10/2/025008

  View details for Web of Science ID 000253713700004

• Full-trajectory diagnosis of laser-driven radiative blast waves in search of thermal plasma instabilities PHYSICAL REVIEW LETTERS Moore, A. S., Gumbrell, E. T., Lazarus, J., Hohenberger, M., Robinson, J. S., Smith, R. A., Plant, T. A., Symes, D. R., Dunne, M. 2008; 100 (5): 055001

  Abstract

  Experimental investigations into the dynamics of cylindrical, laser-driven, high-Mach-number shocks are used to study the thermal cooling instability predicted to occur in astrophysical radiative blast waves. A streaked Schlieren technique measures the full blast-wave trajectory on a single-shot basis, which is key for observing shock velocity oscillations. Electron density profiles and deceleration parameters associated with radiative blast waves were recorded, enabling the calculation of important blast-wave parameters including the fraction of radiated energy, epsilon, as a function of time for comparison with radiation-hydrodynamics simulations.

  View details for DOI 10.1103/PhysRevLett.100.055001

  View details for Web of Science ID 000253019600036

  View details for PubMedID 18352379

• Dynamic imaging of molecules using high order harmonic generation PHYSICAL CHEMISTRY CHEMICAL PHYSICS Marangos, J. P., Baker, S., Kajumba, N., Robinson, J. S., Tisch, J. G., Torres, R. 2008; 10 (1): 35-48

  Abstract

  We review recent progress towards imaging the electronic wavefunctions and nuclear dynamics of small molecules using the high order harmonics emitted when a molecule experiences an intense laser field. We illustrate that the essence of high harmonic emission is contained in the recombination amplitude between the continuum portion of the electronic wavefunction, that is formed through field ionization and which is accelerated and driven back to recollide in the laser field, and the bound electronic state. We review for the non-specialist some recent experimental and theoretical work dealing with high harmonic generation (HHG) in molecules. Particular attention is paid to two types of experiment recently performed in our group. The first of these types of experiment is the measurement of signatures of molecular electronic structure using HHG from molecules with a fixed orientation in space. The second is the use of HHG to track extremely fast proton rearrangement following ionization in light molecules, using the intrinsic temporal variation of the recolliding electron energy to extract these dynamics from measurements of the high harmonics.

  View details for DOI 10.1039/b714126m

  View details for Web of Science ID 000251772400004

  View details for PubMedID 18075681

• Probing Molecular Structure and Dynamics by Laser-Driven Electron Recollisions STRONG FIELD LASER PHYSICS Marangos, J. P., Baker, S., Robinson, J. S., Torres, R., Tisch, J. G., Chirila, C. C., Lein, M., Velotta, R., Altucci, C., Brabec, T. 2008; 134: 209-224

  View details for DOI 10.1007/978-0-387-34755-4_9

  View details for Web of Science ID 000266799800009

• High resolution imaging of colliding blast waves in cluster media Smith, R. A., Lazarus, J., Hohenberger, M., Marocchino, A., Robinson, J. S., Chittenden, J. P., Moore, A. S., Gumbrell, E. T., Dunne, M. IOP PUBLISHING LTD. 2007: B117-B124

  View details for DOI 10.1088/0741-3335/49/12B/S11

  View details for Web of Science ID 000252745900013

• Probing orbital structure of polyatomic molecules by high-order harmonic generation (vol 98, art no 203007, 2007) PHYSICAL REVIEW LETTERS Torres, R., Kajumba, N., Underwood, J. G., Robinson, J. S., Baker, S., Tisch, J. G., de Nalda, R., Bryan, W. A., Velotta, R., Altucci, C., Turcu, I. E., Marangos, J. P. 2007; 98 (23)

  View details for DOI 10.1103/PhysRevLett.98.239903

  View details for Web of Science ID 000247107200059

• Probing orbital structure of polyatomic molecules by high-order harmonic generation PHYSICAL REVIEW LETTERS Torres, R., Kajumba, N., Underwood, J. G., Robinson, J. S., Baker, S., Tisch, J. G., de Nalda, R., Bryan, W. A., Velotta, R., Altucci, C., Turcu, I. E., Marangos, J. P. 2007; 98 (20): 203007

  Abstract

  The effects of electronic structure and symmetry are observed in laser driven high-order harmonic generation for laser aligned conjugated polyatomic molecular systems. The dependence of the harmonic yield on the angle between the molecular axis and the polarization of the driving laser field is seen to contain the fingerprint of the highest occupied molecular orbitals in acetylene and allene, a good quantitative agreement with calculations employing the strong field approximation was found. These measurements support the extension of the recently proposed molecular orbital imaging techniques beyond simple diatomic molecules to larger molecular systems.

  View details for DOI 10.1103/PhysRevLett.98.203007

  View details for Web of Science ID 000246624000020

  View details for PubMedID 17677693

• Investigating the astrophysical applicability of radiative and non-radiative blast wave structure in cluster media Moore, A. S., Lazarus, J., Hohenberger, M., Robinson, J. S., Gumbrell, E. T., Dunne, M., Smith, R. A. SPRINGER. 2007: 139–45

  View details for DOI 10.1007/s10509-006-9266-x

  View details for Web of Science ID 000244995100026

• Characterizing spatio-temporal coupling of extreme ultraviolet ultrashort pulses from high harmonic generation Wyatt, A. S., Witting, T., Monmayrant, A., Walmsley, I. A., Haworth, C., Robinson, J. S., Tisch, J. G., Marangos, J. P., IEEE IEEE. 2007: 703-+

  View details for Web of Science ID 000268751000354

• Probing proton dynamics in molecules on an attosecond timescale Baker, S., Robinson, J. S., Lein, M., Chirila, C. C., Bandulet, H. C., Comtois, D., Villeneuve, D., Kieffer, J. C., Tisch, J. G., Marangos, J. P., IEEE IEEE. 2007: 2400-+

  View details for Web of Science ID 000268751001649

• Half-cycle cutoffs in harmonic spectra and robust carrier-envelope phase retrieval NATURE PHYSICS Haworth, C. A., Chipperfield, L. E., Robinson, J. S., Knight, P. L., Marangos, J. P., Tisch, J. G. 2007; 3 (1): 52-57

  View details for DOI 10.1038/nphys463

  View details for Web of Science ID 000243729900018

• Probing fast nuclear wavepackets in light molecules: monitoring structural rearrangement on an attosecond timescale JOURNAL OF MODERN OPTICS Baker, S., Robinson, J. S., Haworth, C. A., Chirila, C. C., Lein, M., Tisch, J. G., Marangos, J. P. 2007; 54 (7): 1011-1017

  View details for DOI 10.1080/09500340601022516

  View details for Web of Science ID 000246761200009

• Colliding blast waves driven by the interaction of a short-pulse laser with a gas of atomic clusters Smith, R. A., Lazarus, J., Hohenberger, M., Moore, A. S., Robinson, J. S., Gumbrell, E. T., Dunne, M. SPRINGER. 2007: 131–37

  View details for DOI 10.1007/s10509-006-9260-3

  View details for Web of Science ID 000244995100025

• The generation of intense, transform-limited laser pulses with tunable duration from 6 to 30 fs in a differentially pumped hollow fibre APPLIED PHYSICS B-LASERS AND OPTICS Robinson, J. S., Haworth, C. A., Teng, H., Smith, R. A., Marangos, J. P., Tisch, J. G. 2006; 85 (4): 525-529

  View details for DOI 10.1007/s00340-006-2390-z

  View details for Web of Science ID 000242013800007

• Probing proton dynamics in molecules on an attosecond time scale SCIENCE Baker, S., Robinson, J. S., Haworth, C. A., Teng, H., Smith, R. A., Chirila, C. C., Lein, M., Tisch, J. W., Marangos, J. P. 2006; 312 (5772): 424-427

  Abstract

  We demonstrate a technique that uses high-order harmonic generation in molecules to probe nuclear dynamics and structural rearrangement on a subfemtosecond time scale. The chirped nature of the electron wavepacket produced by laser ionization in a strong field gives rise to a similar chirp in the photons emitted upon electron-ion recombination. Use of this chirp in the emitted light allows information about nuclear dynamics to be gained with 100-attosecond temporal resolution, from excitation by an 8-femtosecond pulse, in a single laser shot. Measurements on molecular hydrogen and deuterium agreed well with calculations of ultrafast nuclear dynamics in the H2+ molecule, confirming the validity of the method. We then measured harmonic spectra from CH4 and CD4 to demonstrate a few-femtosecond time scale for the onset of proton rearrangement in methane upon ionization.

  View details for DOI 10.1126/science.1123904

  View details for Web of Science ID 000236941800046

  View details for PubMedID 16513942

• Probing attosecond dynamics by laser driven electron recollisions Marangos, J. P., Baker, S., Robinson, J. S., Haworth, C. A., Chirila, C. C., Lein, M., Chipperfield, L., Tisch, J. G., Roos, C., Haffner, H., Blatt, R. AMER INST PHYSICS. 2006: 303-+

  View details for Web of Science ID 000243101800035

• Control parameters for ion heating and X-ray emission from laser induced cluster explosion APPLIED PHYSICS B-LASERS AND OPTICS Moore, A. S., Mendham, K. J., Symes, D. R., Robinson, J. S., Springate, E., Mason, M. B., Smith, R. A., Tisch, J. W., Marangos, J. P. 2005; 80 (1): 101-107

  View details for DOI 10.1007/s00340-004-1672-6

  View details for Web of Science ID 000225524900016