Probing ultrafast solvation dynamics with high repetition-rate laser / X-ray methodologies
The chemical reactivity of molecules in solution critically depends on a complex interplay among intramolecular processes and interactions with the caging solvation shell, which surrounds a solute molecule. Accordingly, the influence of solvation on the reactivity of chemical and biological molecular species has been the subject of increasingly intense research. Ultrafast time-resolved x-ray measurement techniques that combine picosecond lasers and short-pulse x-rays in laser pump/x-ray probe experiments are powerful tools for studying this interplay in photo-active molecular systems. In a typical laser pump/x-ray probe experiment, a laser pulse excites a molecular sample to create a transient state; an x-ray pulse follows to probe the transient state at a fixed time delay relative to the laser pulse. X-ray spectroscopy and/or scattering signals can then be accumulated over many thousand such pump/probe cycles to satisfy signal-to-noise requirements. Doing so at a series of different time delays then reveals the temporal evolution of...