Ultrafast dynamics and scattering of protic ionic liquids induced by XFEL pulses

Journal of synchrotron radiation 28(5), 1296 - 1308 (2021). doi:10.1107/S1600577521007657 special issue: "Issue on 11th International Workshop on X-ray Radiation Damage to Biological Crystalline Samples"
X-rays are routinely used for structural studies through scattering, and femtosecond X-ray lasers can probe ultrafast dynamics. We aim to capture the femtosecond dynamics of liquid samples using simulations and deconstruct the interplay of ionization and atomic motion within the X-ray laser pulse. This deconstruction is resolution dependent, as ionization influences the low momentum transfers through changes in scattering form factors, while atomic motion has a greater effect at high momentum transfers through loss of coherence. Our methodology uses a combination of classical molecular dynamics and plasma simulation on a protic ionic liquid to quantify the contributions to the scattering signal and how these evolve with time during the X-ray laser pulse. Our method is relevant for studies of organic liquids, biomolecules in solution or any low-Z materials at liquid densities that quickly turn into a plasma while probed with X-rays.Keywords: radiation damage; molecular dynamics; non-local thermodynamic equilibrium; protic ionic liquids; X-ray free-electron lasers.
Published by Wiley-Blackwell, [S.l.]