Sanghoon Song

All Publications

• Terahertz-field activation of polar skyrons. Nature communications Wang, H. H., Stoica, V. A., Dai, C., Paściak, M., Das, S., Yang, T., Gonçalves, M. A., Kulda, J., McCarter, M. R., Mangu, A., Cao, Y., Padma, H., Saha, U., Zhu, D., Sato, T., Song, S., Hoffmann, M. C., Kramer, P., Nelson, S., Sun, Y., Nguyen, Q., Zhang, Z., Ramesh, R., Martin, L. W., Lindenberg, A. M., Chen, L. Q., Freeland, J. W., Hlinka, J., Gopalan, V., Wen, H. 2025; 16 (1): 8994

  Abstract

  Unraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuity at the nanometer scale with nontrivial topology, leading to previously unexplored collective modes. Here, using terahertz-field excitation and femtosecond x-ray diffraction, we discover subterahertz collective modes, dubbed "skyrons", which appear as swirling patterns of atomic displacements functioning as atomic-scale gearsets. The key to activating skyrons is the use of the THz field that couples primarily to skyrmion domain walls. Momentum-resolved time-domain measurements of diffuse scattering reveal an avoided crossing in the dispersion relation of skyrons. Atomistic simulations and dynamical phase-field modeling provide microscopic insights into the three-dimensional crystallographic and polarization dynamics. The amplitude and dispersion of skyrons are demonstrated to be controlled by sample temperature and electric-field bias. The discovery of skyrons and their coupling with terahertz fields opens avenues for ultrafast control of topological polar structures.

  View details for DOI 10.1038/s41467-025-64033-6

  View details for PubMedID 41068083

  View details for PubMedCentralID 9228410

• Determining the nanostructure of polymer foams using 3D ptycho-tomography for inertial fusion energy applications PHYSICS OF PLASMAS Hancock, L., Mertes, K., Carr, A., Xia, X., Sweeney, C., Ikeya, M., Chen, Y., Esposito, V., Hodge, D., Hoidn, O., Martin, W. M., Mettry-Yassa, M., Parisuana, C., Sato, T., Sechrest, Y., Seaberg, M. H., Song, S., Vong, A., White, A., Sandberg, R. L., Gleason, A. E. 2025; 32 (10)

  View details for DOI 10.1063/5.0272192

  View details for Web of Science ID 001592099600001

• Impulsive excitation of squeezed phonons in single crystal germanium by an x-ray laser APPLIED PHYSICS LETTERS Wang, N., Li, H., Sun, Y., Hanlon, D., Huang, Y., Sun, P., She, B., Ornelas-Skarin, C., Teitelbaum, S. W., Sutton, M., Fuoss, P. H., Hastings, J. B., Sato, T., Song, S., Trigo, M., Reis, D. A., Dunne, M., Zhu, D. 2025; 126 (22)

  View details for DOI 10.1063/5.0269800

  View details for Web of Science ID 001506885200008

• Femtosecond x-ray photon correlation spectroscopy enables direct observations of atomic-scale relaxations of glass forming liquids. The Journal of chemical physics Fujita, T., Sun, Y., Li, H., Albert, T. J., Song, S., Sato, T., Moesgaard, J., Cornet, A., Sun, P., Chen, Y., Mo, M., Amini, N., Yang, F., Lucas, P., Esposito, V., Vila-Comamala, J., Wang, N., Mamyrbayev, T., David, C., Hastings, J., Ruta, B., Fuoss, P., Sokolowski-Tinten, K., Zhu, D., Wei, S. 2025; 162 (19)

  Abstract

  Glass-forming liquids exhibit structural relaxation behaviors, reflecting underlying atomic rearrangements on a wide range of timescales and playing a crucial role in determining material properties. However, the relaxation processes on the atomic scale are not well-understood due to the experimental difficulties in directly characterizing the evolving correlations of atomic-scale order in disordered systems. Here, we harness the coherence and ultrashort pulse characteristics of an x-ray free electron laser to directly probe atomic-scale ultrafast relaxation dynamics in the model system Ge15Te85. We demonstrate an analysis strategy for determining the intermediate scattering function by extracting the contrast decay of summed scattering patterns from two rapidly successive, nearly identical femtosecond x-ray pulses generated by a split-delay system. The result indicates a full decorrelation of atomic-scale order on the sub-picosecond timescale, supporting the argument for a high-fluidity fragile state of liquid Ge15Te85 above its dynamic crossover temperature. The demonstrated strategy opens an avenue for experimental studies of relaxation dynamics in liquids, glasses, and other highly disordered systems.

  View details for DOI 10.1063/5.0264574

  View details for PubMedID 40371826

• Structure and ultrafast dynamics of tri-nuclear Ag-/Tl-Pt₂POP₄ complexes in solution STRUCTURAL DYNAMICS-US Lenzen, P., Haldrup, K., Dohn, A. O., Beyer, F., Biasin, E., Christensen, M., Hansen, B. L., Harlang, T., Kjaer, K., Laursen, M., Vester, P., van Driel, T. B., Chollet, M., Glownia, J. M., Hartsock, R. J., Lemke, H. T., Nelson, S., Song, S., Pedersen, K., Gaffney, K. J., Moller, K. B., Nielsen, M. M. 2025; 12 (4)

  View details for DOI 10.1063/4.0000293

  View details for Web of Science ID 001528014400001

  View details for PubMedID 40666623

• Dynamics of nanoscale phase decomposition in laser ablation COMMUNICATIONS MATERIALS Sun, Y., Chen, C., Albert, T. J., Li, H., Arefev, M. I., Chen, Y., Dunne, M., Glownia, J. M., Jerman, M., Hoffmann, M., Hurley, M. J., Mo, M., Nguyen, Q. L., Sato, T., Song, S., Sun, P., Sutton, M., Teitelbaum, S., Valavanis, A. S., Wang, N., Zhu, D., Zhigilei, L. V., Sokolowski-Tinten, K. 2025; 6 (1)

  View details for DOI 10.1038/s43246-025-00785-4

  View details for Web of Science ID 001464672100001

• Hidden domain boundary dynamics toward crystalline perfection. Proceedings of the National Academy of Sciences of the United States of America Mangu, A., Stoica, V. A., Zheng, H., Yang, T., Zhang, M., Wang, H. H., Zu, R., Nguyen, Q. L., Song, S., Das, S., Meisenheimer, P., Donoway, E., Chollet, M., Sun, Y., Turner, J. J., Freeland, J. W., Wen, H., Martin, L. W., Chen, L. Q., Gopalan, V., Zhu, D., Cao, Y., Lindenberg, A. M. 2025; 122 (2): e2407772122

  Abstract

  A central paradigm of nonequilibrium physics concerns the dynamics of heterogeneity and disorder, impacting processes ranging from the behavior of glasses to the emergent functionality of active matter. Understanding these complex mesoscopic systems requires probing the microscopic trajectories associated with irreversible processes, the role of fluctuations and entropy growth, and the timescales on which nonequilibrium responses are ultimately maintained. Approaches that illuminate these processes in model systems may enable a more general understanding of other heterogeneous nonequilibrium phenomena, and potentially define ultimate speed and energy cost limits for information processing technologies. Here, we apply ultrafast single-shot X-ray photon correlation spectroscopy to resolve the nonequilibrium, heterogeneous, and irreversible mesoscale dynamics during a light-induced phase transition in a (PbTiO3)16/(SrTiO3)16 superlattice. Such ferroelectric superlattice systems are a useful platform to study phase transitions and topological dynamics due to their high degree of tunability. This provides an approach for capturing the nucleation of the light-induced phase, the formation of transient mesoscale defects at the boundaries of the nuclei, and the eventual annihilation of these defects, even in systems with complex polarization topologies. We identify a nonequilibrium correlation response spanning >10 orders of magnitude in timescales, with multistep behavior similar to the plateaus observed in supercooled liquids and glasses. We further show how the observed time-dependent long-time correlations can be understood in terms of stochastic and non-Markovian dynamics of domain walls, encoded in waiting-time distributions with power-law tails. This work defines possibilities for probing the nonequilibrium and correlated dynamics of disordered and heterogeneous media.

  View details for DOI 10.1073/pnas.2407772122

  View details for PubMedID 39773030

• Direct observation of ultrafast cluster dynamics in supercritical carbon dioxide using X-ray Photon Correlation Spectroscopy. Nature communications Majumdar, A., Li, H., Muhunthan, P., Späh, A., Song, S., Sun, Y., Chollet, M., Sokaras, D., Zhu, D., Ihme, M. 2024; 15 (1): 10540

  Abstract

  Supercritical fluids exhibit distinct thermodynamic and transport properties, making them of particular interest for a wide range of scientific and engineering applications. These anomalous properties emerge from structural heterogeneities due to the formation of molecular clusters at conditions above the critical point. While the static behavior of these clusters and their effects on the thermodynamic response functions have been recognized, the relation between the ultrafast cluster dynamics and transport properties remains elusive. By measuring the intermediate scattering function in carbon dioxide at conditions near the critical point with X-ray photon correlation spectroscopy, we directly capture the cross-over dynamics between 4 and 13 picoseconds, revealing the transition between ballistic and diffusive motion. Complementary analysis using large-scale molecular dynamics simulations reveals that this behavior arises from collisions between unbound molecules and clusters. This study provides direct evidence of the ultrafast momentum exchange between clusters, which has significant impact on transport properties, solvation processes, and reaction kinetics in supercritical fluids.

  View details for DOI 10.1038/s41467-024-54782-1

  View details for PubMedID 39627208

  View details for PubMedCentralID PMC11615208

• Nanometer-Scale Acoustic Wave Packets Generated by Stochastic Core-Level Photoionization Events PHYSICAL REVIEW X Huang, Y., Sun, P., Teitelbaum, S. W., Li, H., Sun, Y., Wang, N., Song, S., Sato, T., Chollet, M., Osaka, T., Inoue, I., Duncan, R. A., Shin, H., Haber, J., Zhou, J., Bernardi, M., Gu, M., Rondinelli, J. M., Trigo, M., Yabashi, M., Maznev, A. A., Nelson, K. A., Zhu, D., Reis, D. A. 2024; 14 (4)

  View details for DOI 10.1103/PhysRevX.14.041010

  View details for Web of Science ID 001335434300002

• In situ coherent x-ray scattering reveals polycrystalline structure and discrete annealing events in strongly coupled nanocrystal superlattices PHYSICAL REVIEW RESEARCH Hurley, M. J., Tanner, C. P. N., Portner, J., Utterback, J. K., Coropceanu, I., Das, A., Slivka, J. D., Fluerasu, A., Sun, Y., Song, S., Hamerlynck, L. M., Miller, A. H., Bhattacharyya, P., V. Talapin, D., Williams, G. J., Ginsberg, N. S., Teitelbaum, S. W. 2024; 6 (2)

  View details for DOI 10.1103/PhysRevResearch.6.023119

  View details for Web of Science ID 001224127700003

• A versatile pressure-cell design for studying ultrafast molecular-dynamics in supercritical fluids using coherent multi-pulse x-ray scattering. The Review of scientific instruments Muhunthan, P., Li, H., Vignat, G., Toro, E. R., Younes, K., Sun, Y., Sokaras, D., Weiss, T., Rajkovic, I., Osaka, T., Inoue, I., Song, S., Sato, T., Zhu, D., Fulton, J. L., Ihme, M. 2024; 95 (1)

  Abstract

  Supercritical fluids (SCFs) can be found in a variety of environmental and industrial processes. They exhibit an anomalous thermodynamic behavior, which originates from their fluctuating heterogeneous micro-structure. Characterizing the dynamics of these fluids at high temperature and high pressure with nanometer spatial and picosecond temporal resolution has been very challenging. The advent of hard x-ray free electron lasers has enabled the development of novel multi-pulse ultrafast x-ray scattering techniques, such as x-ray photon correlation spectroscopy (XPCS) and x-ray pump x-ray probe (XPXP). These techniques offer new opportunities for resolving the ultrafast microscopic behavior in SCFs at unprecedented spatiotemporal resolution, unraveling the dynamics of their micro-structure. However, harnessing these capabilities requires a bespoke high-pressure and high-temperature sample system that is optimized to maximize signal intensity and address instrument-specific challenges, such as drift in beamline components, x-ray scattering background, and multi-x-ray-beam overlap. We present a pressure cell compatible with a wide range of SCFs with built-in optical access for XPCS and XPXP and discuss critical aspects of the pressure cell design, with a particular focus on the design optimization for XPCS.

  View details for DOI 10.1063/5.0158497

  View details for PubMedID 38170817

• 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

• Ultrafast X-Ray Scattering Reveals Composite Amplitude Collective Mode in the Weyl Charge Density Wave Material (TaSe_{4})_{2}I. Physical review letters Nguyen, Q. L., Duncan, R. A., Orenstein, G., Huang, Y., Krapivin, V., de la Peña, G., Ornelas-Skarin, C., Reis, D. A., Abbamonte, P., Bettler, S., Chollet, M., Hoffmann, M. C., Hurley, M., Kim, S., Kirchmann, P. S., Kubota, Y., Mahmood, F., Miller, A., Osaka, T., Qu, K., Sato, T., Shoemaker, D. P., Sirica, N., Song, S., Stanton, J., Teitelbaum, S. W., Tilton, S. E., Togashi, T., Zhu, D., Trigo, M. 2023; 131 (7): 076901

  Abstract

  We report ultrafast x-ray scattering experiments of the quasi-1D charge density wave (CDW) material (TaSe_{4})_{2}I following ultrafast infrared photoexcitation. From the time-dependent diffraction signal at the CDW sidebands we identify a 0.11 THz amplitude mode derived primarily from a transverse acoustic mode of the high-symmetry structure. From our measurements we determine that this mode interacts with the valence charge indirectly through another collective mode, and that the CDW system in (TaSe_{4})_{2}I has a composite nature supporting multiple dynamically active structural degrees of freedom.

  View details for DOI 10.1103/PhysRevLett.131.076901

  View details for PubMedID 37656841

• Enhanced charge density wave with mobile superconducting vortices in La1.885Sr0.115CuO4. Nature communications Wen, J., He, W., Jang, H., Nojiri, H., Matsuzawa, S., Song, S., Chollet, M., Zhu, D., Liu, Y., Fujita, M., Jiang, J. M., Rotundu, C. R., Kao, C., Jiang, H., Lee, J., Lee, Y. S. 2023; 14 (1): 733

  Abstract

  Superconductivity in the cuprates is found to be intertwined with charge and spin density waves. Determining the interactions between the different types of order is crucial for understanding these important materials. Here, we elucidate the role of the charge density wave (CDW) in the prototypical cuprate La1.885Sr0.115CuO4, by studying the effects of large magnetic fields (H) up to 24 Tesla. At low temperatures (T), the observed CDW peaks reveal two distinct regions in the material: a majority phase with short-range CDW coexisting with superconductivity, and a minority phase with longer-range CDW coexisting with static spin density wave (SDW). With increasing magnetic field, the CDW first grows smoothly in a manner similar to the SDW. However, at high fields we discover a sudden increase in the CDW amplitude upon entering the vortex-liquid state. Our results signify strong coupling of the CDW to mobile superconducting vortices and link enhanced CDW amplitude with local superconducting pairing across the H-T phase diagram.

  View details for DOI 10.1038/s41467-023-36203-x

  View details for PubMedID 36759612

• Characterization of photoinduced normal state through charge density wave in superconducting YBa2Cu3O6.67. Science advances Jang, H., Song, S., Kihara, T., Liu, Y., Lee, S., Park, S., Kim, M., Kim, H., Coslovich, G., Nakata, S., Kubota, Y., Inoue, I., Tamasaku, K., Yabashi, M., Lee, H., Song, C., Nojiri, H., Keimer, B., Kao, C., Lee, J. 2022; 8 (6): eabk0832

  Abstract

  The normal state of high-Tc cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa2Cu3O6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO2 plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

  View details for DOI 10.1126/sciadv.abk0832

  View details for PubMedID 35138893

• Testing the data framework for an AI algorithm in preparation for high data rate X-ray facilities Chen, H., Chitturi, S. R., Plumley, R., Shen, L., Drucker, N. C., Burdet, N., Peng, C., Mardanya, S., Ratner, D., Mishra, A., Yoon, C., Song, S., Chollet, M., Fabbris, G., Dunne, M., Nelson, S., Li, M., Lindenberg, A., Jia, C., Nashed, Y., Bansil, A., Chowdhury, S., Feiguin, A. E., Turner, J. J., Thayer, J. B., IEEE IEEE. 2022: 1-9

  View details for DOI 10.1109/XLOOP56614.2022.00006

  View details for Web of Science ID 000968746500001

• Effects of x-ray free-electron laser pulse intensity on the Mn K beta(1,3) x-ray emission spectrum in photosystem II-A case study for metalloprotein crystals and solutions STRUCTURAL DYNAMICS-US Fransson, T., Alonso-Mori, R., Chatterjee, R., Cheah, M., Ibrahim, M., Hussein, R., Zhang, M., Fuller, F., Gul, S., Kim, I., Simon, P. S., Bogacz, I., Makita, H., de Lichtenberg, C., Song, S., Batyuk, A., Sokaras, D., Massad, R., Doyle, M., Britz, A., Weninger, C., Zouni, A., Messinger, J., Yachandra, V. K., Yano, J., Kern, J., Bergmann, U. 2021; 8 (6): 064302

  Abstract

  In the last ten years, x-ray free-electron lasers (XFELs) have been successfully employed to characterize metalloproteins at room temperature using various techniques including x-ray diffraction, scattering, and spectroscopy. The approach has been to outrun the radiation damage by using femtosecond (fs) x-ray pulses. An example of an important and damage sensitive active metal center is the Mn4CaO5 cluster in photosystem II (PS II), the catalytic site of photosynthetic water oxidation. The combination of serial femtosecond x-ray crystallography and Kβ x-ray emission spectroscopy (XES) has proven to be a powerful multimodal approach for simultaneously probing the overall protein structure and the electronic state of the Mn4CaO5 cluster throughout the catalytic (Kok) cycle. As the observed spectral changes in the Mn4CaO5 cluster are very subtle, it is critical to consider the potential effects of the intense XFEL pulses on the Kβ XES signal. We report here a systematic study of the effects of XFEL peak power, beam focus, and dose on the Mn Kβ1,3 XES spectra in PS II over a wide range of pulse parameters collected over seven different experimental runs using both microcrystal and solution PS II samples. Our findings show that for beam intensities ranging from ∼5 × 1015 to 5 × 1017 W/cm2 at a pulse length of ∼35 fs, the spectral effects are small compared to those observed between S-states in the Kok cycle. Our results provide a benchmark for other XFEL-based XES studies on metalloproteins, confirming the viability of this approach.

  View details for DOI 10.1063/4.0000130

  View details for Web of Science ID 000723107700001

  View details for PubMedID 34849380

  View details for PubMedCentralID PMC8610604

• A Contrast Calibration Protocol for X-ray Speckle Visibility Spectroscopy APPLIED SCIENCES-BASEL Sun, Y., Esposito, V., Hart, P., Hansson, C., Li, H., Nakahara, K., MacArthur, J., Nelson, S., Sato, T., Song, S., Sun, P., Fuoss, P., Sutton, M., Zhu, D. 2021; 11 (21)

  View details for DOI 10.3390/app112110041

  View details for Web of Science ID 000726897500001

• Generation of highly mutually coherent hard-x-ray pulse pairs with an amplitude-splitting delay line PHYSICAL REVIEW RESEARCH Li, H., Sun, Y., Vila-Comamala, J., Sato, T., Song, S., Sun, P., Seaberg, M. H., Wang, N., Hastings, J. B., Dunne, M., Fuoss, P., David, C., Sutton, M., Zhu, D. 2021; 3 (4)

  View details for DOI 10.1103/PhysRevResearch.3.043050

  View details for Web of Science ID 000708677100006

• Laser-induced transient magnons in Sr3Ir2O7 throughout the Brillouin zone PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Mazzone, D. G., Meyers, D., Cao, Y., Vale, J. G., Dashwood, C. D., Shi, Y., James, A. J. A., Robinson, N. J., Lin, J., Thampy, V., Tanaka, Y., Johnson, A. S., Miao, H., Wang, R., Assefa, T. A., Kim, J., Casa, D., Mankowsky, R., Zhu, D., Alonso-Mori, R., Song, S., Yavas, H., Katayama, T., Yabashi, M., Kubota, Y., Owada, S., Liu, J., Yang, J., Konik, R. M., Robinson, I. K., Hill, J. P., McMorrow, D. F., Forst, M., Wall, S., Liu, X., Dean, M. P. M. 2021; 118 (22)

  View details for DOI 10.1073/pnas.2103696118|1of6

  View details for Web of Science ID 000659461200013

• Charge transfer driven by ultrafast spin transition in a CoFe Prussian blue analogue NATURE CHEMISTRY Cammarata, M., Zerdane, S., Balducci, L., Azzolina, G., Mazerat, S., Exertier, C., Trabuco, M., Levantino, M., Alonso-Mori, R., Glownia, J. M., Song, S., Catala, L., Mallah, T., Matar, S. F., Collet, E. 2021; 13 (1): 10-+

  Abstract

  Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin transition, has been debated for decades; it has been beyond reach due to its extreme speed. Here we study this process in a prototype cyanide-bridged CoFe system by femtosecond X-ray and optical absorption spectroscopies, enabling the disentanglement of ultrafast electronic and structural dynamics. Our results demonstrate that it is the spin transition that occurs first on the Co site within ~50 fs, and it is this that drives the subsequent Fe-to-Co charge-transfer within ~200 fs. This study represents a step towards understanding and controlling charge-transfer-based functions using light.

  View details for DOI 10.1038/s41557-020-00597-8

  View details for Web of Science ID 000599012700005

  View details for PubMedID 33288895

• Unusual Breathing Behavior of Optically Excited Barium Titanate Nanocrystals CRYSTALS Diao, J., Cherukara, M., Harder, R., Huang, X., Zhang, F., Chen, B., Ulvestad, A., Song, S., Zhu, D., Keen, D., Robinson, I. 2020; 10 (5)

  View details for DOI 10.3390/cryst10050365

  View details for Web of Science ID 000541423400031

• Femtosecond electronic structure response to high intensity XFEL pulses probed by iron X-ray emission spectroscopy. Scientific reports Alonso-Mori, R. n., Sokaras, D. n., Cammarata, M. n., Ding, Y. n., Feng, Y. n., Fritz, D. n., Gaffney, K. J., Hastings, J. n., Kao, C. C., Lemke, H. T., Maxwell, T. n., Robert, A. n., Schropp, A. n., Seiboth, F. n., Sikorski, M. n., Song, S. n., Weng, T. C., Zhang, W. n., Glenzer, S. n., Bergmann, U. n., Zhu, D. n. 2020; 10 (1): 16837

  Abstract

  We report the time-resolved femtosecond evolution of the K-shell X-ray emission spectra of iron during high intensity illumination of X-rays in a micron-sized focused hard X-ray free electron laser (XFEL) beam. Detailed pulse length dependent measurements revealed that rapid spectral energy shift and broadening started within the first 10 fs of the X-ray illumination at intensity levels between 1017 and 1018 W cm-2. We attribute these spectral changes to the rapid evolution of high-density photoelectron mediated secondary collisional ionization processes upon the absorption of the incident XFEL radiation. These fast electronic processes, occurring at timescales well within the typical XFEL pulse durations (i.e., tens of fs), set the boundary conditions of the pulse intensity and sample parameters where the widely-accepted 'probe-before-destroy' measurement strategy can be adopted for electronic-structure related XFEL experiments.

  View details for DOI 10.1038/s41598-020-74003-1

  View details for PubMedID 33033373

• Time-resolved in situ visualization of the structural response of zeolites during catalysis. Nature communications Kang, J. n., Carnis, J. n., Kim, D. n., Chung, M. n., Kim, J. n., Yun, K. n., An, G. n., Cha, W. n., Harder, R. n., Song, S. n., Sikorski, M. n., Robert, A. n., Thanh, N. H., Lee, H. n., Choi, Y. N., Huang, X. n., Chu, Y. S., Clark, J. N., Song, M. K., Yoon, K. B., Robinson, I. K., Kim, H. n. 2020; 11 (1): 5901

  Abstract

  Zeolites are three-dimensional aluminosilicates having unique properties from the size and connectivity of their sub-nanometer pores, the Si/Al ratio of the anionic framework, and the charge-balancing cations. The inhomogeneous distribution of the cations affects their catalytic performances because it influences the intra-crystalline diffusion rates of the reactants and products. However, the structural deformation regarding inhomogeneous active regions during the catalysis is not yet observed by conventional analytical tools. Here we employ in situ X-ray free electron laser-based time-resolved coherent X-ray diffraction imaging to investigate the internal deformations originating from the inhomogeneous Cu ion distributions in Cu-exchanged ZSM-5 zeolite crystals during the deoxygenation of nitrogen oxides with propene. We show that the interactions between the reactants and the active sites lead to an unusual strain distribution, confirmed by density functional theory simulations. These observations provide insights into the role of structural inhomogeneity in zeolites during catalysis and will assist the future design of zeolites for their applications.

  View details for DOI 10.1038/s41467-020-19728-3

  View details for PubMedID 33214547

• Speckle correlation as a monitor of X-ray free-electron laser induced crystal lattice deformation. Journal of synchrotron radiation Plumley, R. n., Sun, Y. n., Teitelbaum, S. n., Song, S. n., Sato, T. n., Chollet, M. n., Nelson, S. n., Wang, N. n., Sun, P. n., Robert, A. n., Fuoss, P. n., Sutton, M. n., Zhu, D. n. 2020; 27 (Pt 6): 1470–76

  Abstract

  X-ray free-electron lasers (X-FELs) present new opportunities to study ultrafast lattice dynamics in complex materials. While the unprecedented source brilliance enables high fidelity measurement of structural dynamics, it also raises experimental challenges related to the understanding and control of beam-induced irreversible structural changes in samples that can ultimately impact the interpretation of experimental results. This is also important for designing reliable high performance X-ray optical components. In this work, X-FEL beam-induced lattice alterations are investigated by measuring the shot-to-shot evolution of near-Bragg coherent scattering from a single crystalline germanium sample. It is shown that X-ray photon correlation analysis of sequential speckle patterns measurements can be used to monitor the nature and extent of lattice rearrangements. Abrupt, irreversible changes are observed following intermittent high-fluence monochromatic X-ray pulses, thus revealing the existence of a threshold response to X-FEL pulse intensity.

  View details for DOI 10.1107/S1600577520011509

  View details for PubMedID 33147171

• XANES and EXAFS of dilute solutions of transition metals at XFELs. Journal of synchrotron radiation Chatterjee, R., Weninger, C., Loukianov, A., Gul, S., Fuller, F. D., Cheah, M. H., Fransson, T., Pham, C. C., Nelson, S., Song, S., Britz, A., Messinger, J., Bergmann, U., Alonso-Mori, R., Yachandra, V. K., Kern, J., Yano, J. 2019; 26 (Pt 5): 1716–24

  Abstract

  This work has demonstrated that X-ray absorption spectroscopy (XAS), both Mn XANES and EXAFS, of solutions with millimolar concentrations of metal is possible using the femtosecond X-ray pulses from XFELs. Mn XAS data were collected using two different sample delivery methods, a Rayleigh jet and a drop-on-demand setup, with varying concentrations of Mn. Here, a new method for normalization of XAS spectra based on solvent scattering that is compatible with data collection from a highly variable pulsed source is described. The measured XANES and EXAFS spectra of such dilute solution samples are in good agreement with data collected at synchrotron sources using traditional scanning protocols. The procedures described here will enable XFEL-based XAS on dilute biological samples, especially metalloproteins, with low sample consumption. Details of the experimental setup and data analysis methods used in this XANES and EXAFS study are presented. This method will also benefit XAS performed at high-repetition-rate XFELs such as the European XFEL, LCLS-II and LCLS-II-HE.

  View details for DOI 10.1107/S1600577519007550

  View details for PubMedID 31490163

• Anisotropic structural dynamics of monolayer crystals revealed by femtosecond surface X-ray scattering NATURE PHOTONICS Tung, I., Krishnamoorthy, A., Sadasivam, S., Zhou, H., Zhang, Q., Seyler, K. L., Clark, G., Mannebach, E. M., Nyby, C., Ernst, F., Zhu, D., Glownia, J. M., Kozina, M. E., Song, S., Nelson, S., Kumazoe, H., Shimojo, F., Kalia, R. K., Vashishta, P., Darancet, P., Heinz, T. F., Nakano, A., Xu, X., Lindenberg, A. M., Wen, H. 2019; 13 (6): 425-+

  View details for DOI 10.1038/s41566-019-0387-5

  View details for Web of Science ID 000468752300020

• Compact hard x-ray split-delay system based on variable-gap channel-cut crystals OPTICS LETTERS Sun, Y., Wang, N., Song, S., Sun, P., Chollet, M., Sato, T., van Driel, T. B., Nelson, S., Plumley, R., Montana-Lopez, J., Teitelbaum, S. W., Haber, J., Hastings, J. B., Baron, A. Q. R., Sutton, M., Fuoss, P. H., Robert, A., Zhu, D. 2019; 44 (10): 2582–85

  Abstract

  We present the concept and a prototypical implementation of a compact x-ray split-delay system that is capable of performing continuous on-the-fly delay scans over a range of ∼10  ps with sub-100 nanoradian pointing stability. The system consists of four channel-cut silicon crystals, two of which have gradually varying gap sizes from intentional 5 deg asymmetric cuts. The delay adjustment is realized by linear motions of these two monolithic varying-gap channel cuts, where the x-ray beam experiences pairs of anti-parallel reflections, and thus becomes less sensitive in output beam pointing to motion imperfections of the translation stages. The beam splitting is accomplished by polished crystal edges. A high degree of mutual coherence between the two branches at the focus is observed by analyzing small-angle coherent x-ray scattering patterns. We envision a wide range of applications including single-shot x-ray pulse temporal diagnostics, studies of high-intensity x-ray-matter interactions, as well as measurement of dynamics in disordered material systems using split-pulse x-ray photon correlation spectroscopy.

  View details for DOI 10.1364/OL.44.002582

  View details for Web of Science ID 000467906400050

  View details for PubMedID 31090737

• The Macromolecular Femtosecond Crystallography Instrument at the Linac Coherent Light Source JOURNAL OF SYNCHROTRON RADIATION Sierra, R. G., Batyuk, A., Sun, Z., Aquila, A., Hunter, M. S., Lane, T. J., Liang, M., Yoon, C., Alonso-Mori, R., Armenta, R., Castagna, J., Hollenbeck, M., Osier, T. O., Hayes, M., Aldrich, J., Curtis, R., Koglin, J. E., Rendahl, T., Rodriguez, E., Carbajo, S., Guillet, S., Paul, R., Hart, P., Nakahara, K., Carini, G., DeMirci, H., Dao, E., Hayes, B. M., Rao, Y. P., Chollet, M., Feng, Y., Fuller, F. D., Kupitz, C., Sato, T., Seaberg, M. H., Song, S., van Driel, T. B., Yavas, H., Zhu, D., Cohen, A. E., Wakatsuki, S., Boutet, S. 2019; 26: 346–57

  View details for DOI 10.1107/S1600577519001577

  View details for Web of Science ID 000460859600007

• The Macromolecular Femtosecond Crystallography Instrument at the Linac Coherent Light Source. Journal of synchrotron radiation Sierra, R. G., Batyuk, A. n., Sun, Z. n., Aquila, A. n., Hunter, M. S., Lane, T. J., Liang, M. n., Yoon, C. H., Alonso-Mori, R. n., Armenta, R. n., Castagna, J. C., Hollenbeck, M. n., Osier, T. O., Hayes, M. n., Aldrich, J. n., Curtis, R. n., Koglin, J. E., Rendahl, T. n., Rodriguez, E. n., Carbajo, S. n., Guillet, S. n., Paul, R. n., Hart, P. n., Nakahara, K. n., Carini, G. n., DeMirci, H. n., Dao, E. H., Hayes, B. M., Rao, Y. P., Chollet, M. n., Feng, Y. n., Fuller, F. D., Kupitz, C. n., Sato, T. n., Seaberg, M. H., Song, S. n., van Driel, T. B., Yavas, H. n., Zhu, D. n., Cohen, A. E., Wakatsuki, S. n., Boutet, S. n. 2019; 26 (Pt 2): 346–57

  Abstract

  The Macromolecular Femtosecond Crystallography (MFX) instrument at the Linac Coherent Light Source (LCLS) is the seventh and newest instrument at the world's first hard X-ray free-electron laser. It was designed with a primary focus on structural biology, employing the ultrafast pulses of X-rays from LCLS at atmospheric conditions to overcome radiation damage limitations in biological measurements. It is also capable of performing various time-resolved measurements. The MFX design consists of a versatile base system capable of supporting multiple methods, techniques and experimental endstations. The primary techniques supported are forward scattering and crystallography, with capabilities for various spectroscopic methods and time-resolved measurements. The location of the MFX instrument allows for utilization of multiplexing methods, increasing user access to LCLS by running multiple experiments simultaneously.

  View details for PubMedID 30855242

• First X-ray test of the Icarus nanosecond-gated camera Hart, P. A., Carpenter, A., Claus, L., Damiani, D., Dayton, M., Decker, F., Gleason, A., Heimann, P., Hurd, E., McBride, E., Nelson, S., Sanchez, M., Song, S., Zhu, D. edited by Tschentscher, T., Patthey, L., Tiedtke, K., Zangrando, M. SPIE-INT SOC OPTICAL ENGINEERING. 2019

  View details for DOI 10.1117/12.2520974

  View details for Web of Science ID 000502119600004

• Higher-order modes at FELs: a machine interpretation Sun, P., Sun, Y., Zhu, D., Song, S., Li, H., Chollet, M., Seaberg, M., Hastings, J. B., Robert, A., Sutton, M., Feng, Y. edited by Tschentscher, T., Patthey, L., Tiedtke, K., Zangrando, M. SPIE-INT SOC OPTICAL ENGINEERING. 2019

  View details for DOI 10.1117/12.2522912

  View details for Web of Science ID 000502119600001

• Pulse intensity characterization of the LCLS nanosecond double-bunch mode of operation JOURNAL OF SYNCHROTRON RADIATION Sun, Y., Decker, F., Turner, J., Song, S., Robert, A., Zhu, D. 2018; 25: 642–49

  Abstract

  The recent demonstration of the `nanosecond double-bunch' operation mode, i.e. two X-ray pulses separated in time between 0.35 and hundreds of nanoseconds and by increments of 0.35 ns, offers new opportunities to investigate ultrafast dynamics in diverse systems of interest. However, in order to reach its full potential, this mode of operation requires the precise characterization of the intensity of each X-ray pulse within each pulse pair for any time separation. Here, a transmissive single-shot diagnostic that achieves this goal for time separations larger than 0.7 ns with a precision better than 5% is presented. It also provides real-time monitoring feedback to help tune the accelerator parameters to deliver double pulse intensity distributions optimized for specific experimental goals.

  View details for PubMedID 29714175

• Laser power meters as an X-ray power diagnostic for LCLS-II Heimann, P., Moeller, S., Carbajo, S., Song, S., Dakovski, G., Nordlund, D., Fritz, D. INT UNION CRYSTALLOGRAPHY. 2018: 72–76

  Abstract

  For the LCLS-II X-ray instruments, laser power meters are being developed as compact X-ray power diagnostics to operate at soft and tender X-ray photon energies. These diagnostics can be installed at various locations along an X-ray free-electron laser (FEL) beamline in order to monitor the transmission of X-ray optics along the beam path. In addition, the power meters will be used to determine the absolute X-ray power at the endstations. Here, thermopile power meters, which measure average power, and have been chosen primarily for their compatibility with the high repetition rates at LCLS-II, are evaluated. A number of characteristics in the soft X-ray range are presented including linearity, calibrations conducted with a photodiode and a gas monitor detector as well as ultra-high-vacuum compatibility tests using residual gas analysis. The application of these power meters for LCLS-II and other X-ray FEL sources is discussed.

  View details for DOI 10.1107/S1600577517014096

  View details for Web of Science ID 000418593300012

  View details for PubMedID 29271754

  View details for PubMedCentralID PMC5741121

• Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides NANO LETTERS Mannebach, E. M., Nyby, C., Ernst, F., Zhou, Y., Tolsma, J., Li, Y., Sher, M., Tung, I., Zhou, H., Zhang, Q., Seyler, K. L., Clark, G., Lin, Y., Zhu, D., Glownia, J. M., Kozina, M. E., Song, S., Nelson, S., Mehta, A., Yu, Y., Pant, A., Aslan, O., Raja, A., Guo, Y., DiChiara, A., Mao, W., Cao, L., Tongay, S., Sun, J., Singh, D. J., Heinz, T. F., Xu, X., MacDonald, A. H., Reed, E., Wen, H., Lindenberg, A. M. 2017; 17 (12): 7761-7766

  View details for DOI 10.1021/acs.nanolett.7b03955

  View details for Web of Science ID 000418393300081

• Coherent structural trapping through wave packet dispersion during photoinduced spin state switching NATURE COMMUNICATIONS Lemke, H. T., Kjaer, K. S., Hartsock, R., van Driel, T. B., Chollet, M., Glownia, J. M., Song, S., Zhu, D., Pace, E., Matar, S. F., Nielsen, M. M., Benfatto, M., Gaffney, K. J., Collet, E., Cammarata, M. 2017; 8

  Abstract

  The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3](2+) compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.

  View details for DOI 10.1038/ncomms15342

  View details for Web of Science ID 000401959300001

  View details for PubMedID 28537270

• Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers. Nature methods Fuller, F. D., Gul, S., Chatterjee, R., Burgie, E. S., Young, I. D., Lebrette, H., Srinivas, V., Brewster, A. S., Michels-Clark, T., Clinger, J. A., Andi, B., Ibrahim, M., Pastor, E., de Lichtenberg, C., Hussein, R., Pollock, C. J., Zhang, M., Stan, C. A., Kroll, T., Fransson, T., Weninger, C., Kubin, M., Aller, P., Lassalle, L., Bräuer, P., Miller, M. D., Amin, M., Koroidov, S., Roessler, C. G., Allaire, M., Sierra, R. G., Docker, P. T., Glownia, J. M., Nelson, S., Koglin, J. E., Zhu, D., Chollet, M., Song, S., Lemke, H., Liang, M., Sokaras, D., Alonso-Mori, R., Zouni, A., Messinger, J., Bergmann, U., Boal, A. K., Bollinger, J. M., Krebs, C., Högbom, M., Phillips, G. N., Vierstra, R. D., Sauter, N. K., Orville, A. M., Kern, J., Yachandra, V. K., Yano, J. 2017

  Abstract

  X-ray crystallography at X-ray free-electron laser sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy, both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing insights into the interplay between the protein structure and dynamics and the chemistry at an active site. The implementation of such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly affects the data quality. We present here a robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method.

  View details for DOI 10.1038/nmeth.4195

  View details for PubMedID 28250468

  View details for PubMedCentralID PMC5376230

• Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides. Nano letters Mannebach, E. M., Nyby, C. n., Ernst, F. n., Zhou, Y. n., Tolsma, J. n., Li, Y. n., Sher, M. J., Tung, I. C., Zhou, H. n., Zhang, Q. n., Seyler, K. L., Clark, G. n., Lin, Y. n., Zhu, D. n., Glownia, J. M., Kozina, M. E., Song, S. n., Nelson, S. n., Mehta, A. n., Yu, Y. n., Pant, A. n., Aslan, O. B., Raja, A. n., Guo, Y. n., DiChiara, A. n., Mao, W. n., Cao, L. n., Tongay, S. n., Sun, J. n., Singh, D. J., Heinz, T. F., Xu, X. n., MacDonald, A. H., Reed, E. n., Wen, H. n., Lindenberg, A. M. 2017; 17 (12): 7761–66

  Abstract

  Modulation of weak interlayer interactions between quasi-two-dimensional atomic planes in the transition metal dichalcogenides (TMDCs) provides avenues for tuning their functional properties. Here we show that above-gap optical excitation in the TMDCs leads to an unexpected large-amplitude, ultrafast compressive force between the two-dimensional layers, as probed by in situ measurements of the atomic layer spacing at femtosecond time resolution. We show that this compressive response arises from a dynamic modulation of the interlayer van der Waals interaction and that this represents the dominant light-induced stress at low excitation densities. A simple analytic model predicts the magnitude and carrier density dependence of the measured strains. This work establishes a new method for dynamic, nonequilibrium tuning of correlation-driven dispersive interactions and of the optomechanical functionality of TMDC quasi-two-dimensional materials.

  View details for PubMedID 29119791

• Focus characterization at an X-ray free-electron laser by coherent scattering and speckle analysis JOURNAL OF SYNCHROTRON RADIATION Sikorski, M., Song, S., Schropp, A., Seiboth, F., Feng, Y., Alonso-Mori, R., Chollet, M., Lemke, H. T., Sokaras, D., Weng, T., Zhang, W., Robert, A., Zhu, D. 2015; 22: 599-605

  Abstract

  X-ray focus optimization and characterization based on coherent scattering and quantitative speckle size measurements was demonstrated at the Linac Coherent Light Source. Its performance as a single-pulse free-electron laser beam diagnostic was tested for two typical focusing configurations. The results derived from the speckle size/shape analysis show the effectiveness of this technique in finding the focus' location, size and shape. In addition, its single-pulse compatibility enables users to capture pulse-to-pulse fluctuations in focus properties compared with other techniques that require scanning and averaging.

  View details for DOI 10.1107/S1600577515004361

  View details for Web of Science ID 000353920300021

  View details for PubMedID 25931074

  View details for PubMedCentralID PMC4416675

• Photon-in photon-out hard X-ray spectroscopy at the Linac Coherent Light Source JOURNAL OF SYNCHROTRON RADIATION Alonso-Mori, R., Sokaras, D., Zhu, D., Kroll, T., Chollet, M., Feng, Y., Glownia, J. M., Kern, J., Lemke, H. T., Nordlund, D., Robert, A., Sikorski, M., Song, S., Weng, T., Bergmann, U. 2015; 22: 612-620

  Abstract

  X-ray free-electron lasers (FELs) have opened unprecedented possibilities to study the structure and dynamics of matter at an atomic level and ultra-fast timescale. Many of the techniques routinely used at storage ring facilities are being adapted for experiments conducted at FELs. In order to take full advantage of these new sources several challenges have to be overcome. They are related to the very different source characteristics and its resulting impact on sample delivery, X-ray optics, X-ray detection and data acquisition. Here it is described how photon-in photon-out hard X-ray spectroscopy techniques can be applied to study the electronic structure and its dynamics of transition metal systems with ultra-bright and ultra-short FEL X-ray pulses. In particular, some of the experimental details that are different compared with synchrotron-based setups are discussed and illustrated by recent measurements performed at the Linac Coherent Light Source.

  View details for DOI 10.1107/S1600577515004488

  View details for Web of Science ID 000353920300023

  View details for PubMedID 25931076

  View details for PubMedCentralID PMC4416677

• Demonstration of Feasibility of X-Ray Free Electron Laser Studies of Dynamics of Nanoparticles in Entangled Polymer Melts SCIENTIFIC REPORTS Carnis, J., Cha, W., Wingert, J., Kang, J., Jiang, Z., Song, S., Sikorski, M., Robert, A., Gutt, C., Chen, S., Dai, Y., Ma, Y., Guo, H., Lurio, L. B., Shpyrko, O., Narayanan, S., Cui, M., Kosif, I., Emrick, T., Russell, T. P., Lee, H., Yu, C., Gruebel, G., Sinha, S. K., Kim, H. 2014; 4: 6017

  Abstract

  The recent advent of hard x-ray free electron lasers (XFELs) opens new areas of science due to their exceptional brightness, coherence, and time structure. In principle, such sources enable studies of dynamics of condensed matter systems over times ranging from femtoseconds to seconds. However, the studies of "slow" dynamics in polymeric materials still remain in question due to the characteristics of the XFEL beam and concerns about sample damage. Here we demonstrate the feasibility of measuring the relaxation dynamics of gold nanoparticles suspended in polymer melts using X-ray photon correlation spectroscopy (XPCS), while also monitoring eventual X-ray induced damage. In spite of inherently large pulse-to-pulse intensity and position variations of the XFEL beam, measurements can be realized at slow time scales. The X-ray induced damage and heating are less than initially expected for soft matter materials.

  View details for PubMedID 25109363

• Core-shell strain structure of zeolite microcrystals NATURE MATERIALS Cha, W., Jeong, N., Song, S., Park, H., Tung Cao Thanh Pham, Harder, R., Lim, B., Xiong, G., Ahn, D., McNulty, I., Kim, J., Yoon, K., Robinson, I. K., Kim, H. 2013; 12 (8): 729-734

  Abstract

  Zeolites are crystalline aluminosilicate minerals featuring a network of 0.3-1.5-nm-wide pores, used in industry as catalysts for hydrocarbon interconversion, ion exchangers, molecular sieves and adsorbents. For improved applications, it is highly useful to study the distribution of internal local strains because they sensitively affect the rates of adsorption and diffusion of guest molecules within zeolites. Here, we report the observation of an unusual triangular deformation field distribution in ZSM-5 zeolites by coherent X-ray diffraction imaging, showing the presence of a strain within the crystal arising from the heterogeneous core-shell structure, which is supported by finite element model calculation and confirmed by fluorescence measurement. The shell is composed of H-ZSM-5 with intrinsic negative thermal expansion whereas the core exhibits a different thermal expansion behaviour due to the presence of organic template residues, which usually remain when the starting materials are insufficiently calcined. Engineering such strain effects could have a major impact on the design of future catalysts.

  View details for DOI 10.1038/NMAT3698

  View details for Web of Science ID 000322119100019

  View details for PubMedID 23832126

• A WORKFLOW BASED CLINICAL DECISION SUPPORT SYSTEM THROUGH INTEGRATION OF CLINICAL WORKFLOW AND KNOWLEDGE PROCESSING INTERNATIONAL JOURNAL OF INNOVATIVE COMPUTING INFORMATION AND CONTROL Lee, J., Jang, J., Shim, B., Kim, S., Kim, J., Kim, H., Song, S., Kim, J., Cho, I., Kim, Y. 2012; 8 (7B): 5251-5264

  View details for Web of Science ID 000306679700022

• Importance of Solubilizing Group and Backbone Planarity in Low Band Gap Polymers for High Performance Ambipolar field-effect Transistors CHEMISTRY OF MATERIALS Lee, J., Son, S., Song, S., Kim, H., Lee, D., Kim, K., Ko, M., Choi, D., Kim, B., Cho, J. 2012; 24 (7): 1316-1323

  View details for DOI 10.1021/cm2037487

  View details for Web of Science ID 000302487500010

• Exploration of crystal strains using coherent x-ray diffraction NEW JOURNAL OF PHYSICS Cha, W., Song, S., Jeong, N., Harder, R., Yoon, K., Robinson, I. K., Kim, H. 2010; 12

  View details for DOI 10.1088/1367-2630/12/3/035022

  View details for Web of Science ID 000276349600021

• Second Harmonic Generation from Bi_3.75La_0.25Ti₃O₁₂ Thin Films Grown by Sol-gel Method Min, H., Jeon, Y., Park, S., Kwon, H., Pak, J., Park, D., Song, S., Cheong, H., Park, G., Kim, H., Kim, D. KOREAN PHYSICAL SOC. 2009: 1278-1281

  View details for DOI 10.3938/jkps.55.1278

  View details for Web of Science ID 000269886800017

• Surface Dynamics of "Dry" Homopolymer Brushes MACROMOLECULES Akgun, B., Ugur, G., Jiang, Z., Narayanan, S., Song, S., Lee, H., Brittain, W. J., Kim, H., Sinha, S. K., Foster, M. D. 2009; 42 (3): 737-741

  View details for DOI 10.1021/ma801279z

  View details for Web of Science ID 000263035100024

• Current Status of Women in Physics in Korea-and the New Physics Camp Initiative for High School Girls Kim, H., Song, S., Park, H., Park, J., An, J., Park, J., Yim, H., Song, J., Yoon, J., Park, Y. edited by Hartline, B. K., Horton, K. R., Kaicher, C. M. AMER INST PHYSICS. 2009: 132-+

  View details for Web of Science ID 000267264900045

• Entanglement Effects in Capillary Waves on Liquid Polymer Films PHYSICAL REVIEW LETTERS Jiang, Z., Mukhopadhyay, M. K., Song, S., Narayanan, S., Lurio, L. B., Kim, H., Sinha, S. K. 2008; 101 (24): 246104

  Abstract

  Overdamped surface capillary wave relaxations on molten polymer films were measured using x-ray photon correlation spectroscopy. We found a transition from a single through a stretched to another single exponential regime as the temperature is decreased from well above to near the bulk glass transition temperature. A universal scaling of the dynamics was discovered over a wide range of film thicknesses, temperatures, and molecular weights (except in the multiple relaxation regime). These observations are justified by hydrodynamic theory and the time-temperature superposition principle by considering an effective viscosity instead of the bulk zero shear viscosity.

  View details for DOI 10.1103/PhysRevLett.101.246104

  View details for Web of Science ID 000261704100036

  View details for PubMedID 19113637

• Study of thermal degradation of organic light emitting device structures by X-ray scattering Lee, Y., Lee, H., Byun, Y., Song, S., Kim, J., Eom, D., Cha, W., Park, S., Kim, J., Kim, H. ELSEVIER SCIENCE SA. 2007: 5674-5677

  View details for DOI 10.1016/j.tsf.2006.12.018

  View details for Web of Science ID 000246548300030