Institute Affiliations


All Publications


  • 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)
  • Response of fs-Laser-Irradiated Diamond by Ultrafast Electron Diffraction JOURNAL OF PHYSICAL CHEMISTRY C Bernal, F., Riffe, E. J., Devlin, S. W., Hamel, S., Lindsey, R. K., Reid, A. H., Mo, M., Luo, D., Kramer, P., Shen, X., Nadarajah, A., Stacey, A., Prawer, S., Whitley, H. D., Schwartz, C. P., Saykally, R. J. 2024
  • Multi-objective Bayesian active learning for MeV-ultrafast electron diffraction. Nature communications Ji, F., Edelen, A., Roussel, R., Shen, X., Miskovich, S., Weathersby, S., Luo, D., Mo, M., Kramer, P., Mayes, C., Othman, M. A., Nanni, E., Wang, X., Reid, A., Minitti, M., England, R. J. 2024; 15 (1): 4726

    Abstract

    Ultrafast electron diffraction using MeV energy beams(MeV-UED) has enabled unprecedented scientific opportunities in the study of ultrafast structural dynamics in a variety of gas, liquid and solid state systems. Broad scientific applications usually pose different requirements for electron probe properties. Due to the complex, nonlinear and correlated nature of accelerator systems, electron beam property optimization is a time-taking process and often relies on extensive hand-tuning by experienced human operators. Algorithm based efficient online tuning strategies are highly desired. Here, we demonstrate multi-objective Bayesian active learning for speeding up online beam tuning at the SLAC MeV-UED facility. The multi-objective Bayesian optimization algorithm was used for efficiently searching the parameter space and mapping out the Pareto Fronts which give the trade-offs between key beam properties. Such scheme enables an unprecedented overview of the global behavior of the experimental system and takes a significantly smaller number of measurements compared with traditional methods such as a grid scan. This methodology can be applied in other experimental scenarios that require simultaneously optimizing multiple objectives by explorations in high dimensional, nonlinear and correlated systems.

    View details for DOI 10.1038/s41467-024-48923-9

    View details for PubMedID 38830874

    View details for PubMedCentralID PMC11148007

  • DC electrical conductivity measurements of warm dense matter using ultrafast THz radiation PHYSICS OF PLASMAS Ofori-Okai, B. K., Descamps, A., McBride, E. E., Mo, M. Z., Weinmann, A., Seipp, L. E., Ali, S. J., Chen, Z., Fletcher, L. B., Glenzer, S. H. 2024; 31 (4)

    View details for DOI 10.1063/5.0193854

    View details for Web of Science ID 001206857800002

  • Direct observation of strong momentum-dependent electron-phonon coupling in a metal. Science advances Mo, M., Tamm, A., Metsanurk, E., Chen, Z., Wang, L., Frost, M., Hartley, N. J., Ji, F., Pandolfi, S., Reid, A. H., Sun, P., Shen, X., Wang, Y., Wang, X., Glenzer, S., Correa, A. A. 2024; 10 (11): eadk9051

    Abstract

    Phonon scattering in metals is one of the most fundamental processes in materials science. However, understanding such processes has remained challenging and requires detailed information on interactions between phonons and electrons. We use an ultrafast electron diffuse scattering technique to resolve the nonequilibrium phonon dynamics in femtosecond-laser-excited tungsten in both time and momentum. We determine transient populations of phonon modes which show strong momentum dependence initiated by electron-phonon coupling. For phonons near Brillouin zone border, we observe a transient rise in their population on a timescale of approximately 1 picosecond driven by the strong electron-phonon coupling, followed by a slow decay on a timescale of approximately 8 picosecond governed by the weaker phonon-phonon relaxation process. We find that the exceptional harmonicity of tungsten is needed for isolating the two processes, resulting in long-lived nonequilibrium phonons in a pure metal. Our finding highlights that electron-phonon scattering can be the determinant factor in the phonon thermal transport of metals.

    View details for DOI 10.1126/sciadv.adk9051

    View details for PubMedID 38478610

  • Evidence for phonon hardening in laser-excited gold using x-ray diffraction at a hard x-ray free electron laser. Science advances Descamps, A., Ofori-Okai, B. K., Bistoni, O., Chen, Z., Cunningham, E., Fletcher, L. B., Hartley, N. J., Hastings, J. B., Khaghani, D., Mo, M., Nagler, B., Recoules, V., Redmer, R., Schörner, M., Senesky, D. G., Sun, P., Tsai, H. E., White, T. G., Glenzer, S. H., McBride, E. E. 2024; 10 (6): eadh5272

    Abstract

    Studies of laser-heated materials on femtosecond timescales have shown that the interatomic potential can be perturbed at sufficiently high laser intensities. For gold, it has been postulated to undergo a strong stiffening leading to an increase of the phonon energies, known as phonon hardening. Despite efforts to investigate this behavior, only measurements at low absorbed energy density have been performed, for which the interpretation of the experimental data remains ambiguous. By using in situ single-shot x-ray diffraction at a hard x-ray free-electron laser, the evolution of diffraction line intensities of laser-excited Au to a higher energy density provides evidence for phonon hardening.

    View details for DOI 10.1126/sciadv.adh5272

    View details for PubMedID 38335288

  • Sub-micron thick liquid sheets produced by isotropically etched glass nozzles. Lab on a chip Crissman, C. J., Mo, M., Chen, Z., Yang, J., Huyke, D. A., Glenzer, S. H., Ledbetter, K., F Nunes, J. P., Ng, M. L., Wang, H., Shen, X., Wang, X., DePonte, D. P. 2022

    Abstract

    We report on the design and testing of glass nozzles used to produce liquid sheets. The sheet nozzles use a single converging channel chemically etched into glass wafers by standard lithographic methods. Operation in ambient air and vacuum was demonstrated. The measured sheet thickness ranges over one order of magnitude with the smallest thickness of 250 nm and the largest of 2.5 mum. Sheet thickness was shown to be independent of liquid flow rate, and dependent on the nozzle outlet area. Sheet surface roughness was dependent on nozzle surface finish and was on the order of 10 nm for polished nozzles. Electron transmission data is presented for various sheet thicknesses near the MeV mean free path and the charge pair distribution function for D2O is determined from electron scattering data.

    View details for DOI 10.1039/d1lc00757b

    View details for PubMedID 35234235

  • Ultrafast visualization of incipient plasticity in dynamically compressed matter. Nature communications Mo, M., Tang, M., Chen, Z., Peterson, J. R., Shen, X., Baldwin, J. K., Frost, M., Kozina, M., Reid, A., Wang, Y., E, J., Descamps, A., Ofori-Okai, B. K., Li, R., Luo, S., Wang, X., Glenzer, S. 2022; 13 (1): 1055

    Abstract

    Plasticity is ubiquitous and plays a critical role in material deformation and damage; it inherently involves the atomistic length scale and picosecond time scale. A fundamental understanding of the elastic-plastic deformation transition, in particular, incipient plasticity, has been a grand challenge in high-pressure and high-strain-rate environments, impeded largely by experimental limitations on spatial and temporal resolution. Here, we report femtosecond MeV electron diffraction measurements visualizing the three-dimensional (3D) response of single-crystal aluminum to the ultrafast laser-induced compression. We capture lattice transitioning from a purely elastic to a plastically relaxed state within 5 ps, after reaching an elastic limit of~25 GPa. Our results allow the direct determination of dislocation nucleation and transport that constitute the underlying defect kinetics of incipient plasticity. Large-scale molecular dynamics simulations show good agreement with the experiment and provide an atomic-level description of the dislocation-mediated plasticity.

    View details for DOI 10.1038/s41467-022-28684-z

    View details for PubMedID 35217665

  • Effect of lattice excitations on transient near-edge x-ray absorption spectroscopy PHYSICAL REVIEW B Rothenbach, N., Gruner, M. E., Ollefs, K., Schmitz-Antoniak, C., Salamon, S., Zhou, P., Li, R., Mo, M., Park, S., Shen, X., Weathersby, S., Yang, J., Wang, X. J., Sipr, O., Ebert, H., Sokolowski-Tinten, K., Pentcheva, R., Bovensiepen, U., Eschenlohr, A., Wende, H. 2021; 104 (14)
  • Imaging the short-lived hydroxyl-hydronium pair in ionized liquid water. Science (New York, N.Y.) Lin, M., Singh, N., Liang, S., Mo, M., Nunes, J. P., Ledbetter, K., Yang, J., Kozina, M., Weathersby, S., Shen, X., Cordones, A. A., Wolf, T. J., Pemmaraju, C. D., Ihme, M., Wang, X. J. 2021; 374 (6563): 92-95

    Abstract

    [Figure: see text].

    View details for DOI 10.1126/science.abg3091

    View details for PubMedID 34591617

  • Observation of a highly conductive warm dense state of water with ultrafast pump-probe free-electron-laser measurements MATTER AND RADIATION AT EXTREMES Chen, Z., Na, X., Curry, C. B., Liang, S., French, M., Descamps, A., DePonte, D. P., Koralek, J. D., Kim, J. B., Lebovitz, S., Nakatsutsumi, M., Ofori-Okai, B. K., Redmer, R., Roedel, C., Schorner, M., Skruszewicz, S., Sperling, P., Toleikis, S., Mo, M. Z., Glenzer, S. H. 2021; 6 (5)

    View details for DOI 10.1063/5.0043726

    View details for Web of Science ID 000681018600001

  • Fast attenuation of high-frequency acoustic waves in bicontinuous nanoporous gold APPLIED PHYSICS LETTERS Zheng, Q., Tian, Y., Shen, X., Sokolowski-Tinten, K., Li, R. K., Chen, Z., Mo, M. Z., Wang, Z. L., Liu, P., Fujita, T., Weathersby, S. P., Yang, J., Wang, X. J., Chen, M. W. 2021; 119 (6)

    View details for DOI 10.1063/5.0055391

    View details for Web of Science ID 000683519300015

  • Ultrafast visualization of phase transitions in nonequilibrium warm dense matter MRS BULLETIN Mo, M., Chen, Z., Glenzer, S. 2021
  • Direct observation of ultrafast hydrogen bond strengthening in liquid water. Nature Yang, J., Dettori, R., Nunes, J. P., List, N. H., Biasin, E., Centurion, M., Chen, Z., Cordones, A. A., Deponte, D. P., Heinz, T. F., Kozina, M. E., Ledbetter, K., Lin, M., Lindenberg, A. M., Mo, M., Nilsson, A., Shen, X., Wolf, T. J., Donadio, D., Gaffney, K. J., Martinez, T. J., Wang, X. 2021; 596 (7873): 531-535

    Abstract

    Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network1, including unusually efficient vibrational energy redistribution and relaxation2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04A on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch.

    View details for DOI 10.1038/s41586-021-03793-9

    View details for PubMedID 34433948

  • Structure retrieval in liquid-phase electron scattering. Physical chemistry chemical physics : PCCP Yang, J., Nunes, J. P., Ledbetter, K., Biasin, E., Centurion, M., Chen, Z., Cordones, A. A., Crissman, C., Deponte, D. P., Glenzer, S. H., Lin, M., Mo, M., Rankine, C. D., Shen, X., Wolf, T. J., Wang, X. 2020

    Abstract

    Electron scattering on liquid samples has been enabled recently by the development of ultrathin liquid sheet technologies. The data treatment of liquid-phase electron scattering has been mostly reliant on methodologies developed for gas electron diffraction, in which theoretical inputs and empirical fittings are often needed to account for the atomic form factor and remove the inelastic scattering background. In this work, we present an alternative data treatment method that is able to retrieve the radial distribution of all the charged particle pairs without the need of either theoretical inputs or empirical fittings. The merits of this new method are illustrated through the retrieval of real-space molecular structure from experimental electron scattering patterns of liquid water, carbon tetrachloride, chloroform, and dichloromethane.

    View details for DOI 10.1039/d0cp06045c

    View details for PubMedID 33367391

  • Synthesis of Macroscopic Single Crystals of Ge2Sb2Te5 via Single-Shot Femtosecond Optical Excitation CRYSTAL GROWTH & DESIGN Zajac, M., Sood, A., Kim, T. R., Mo, M., Kozina, M., Park, S., Shen, X., Guzelturk, B., Lin, M., Yang, J., Weathersby, S., Wang, X., Lindenberg, A. M. 2020; 20 (10): 6660–67
  • Characterization of defect clusters in ion-irradiated tungsten by X-Ray diffuse scattering JOURNAL OF NUCLEAR MATERIALS Sun, P., Wang, Y., Frost, M., Schoenwaelder, C., Levitan, A. L., Mo, M., Chen, Z., Hastings, J. B., Tynan, G. R., Glenzer, S. H., Heimann, P. 2018; 510: 322–30