Anisotropic X-Ray Scattering of Transiently Oriented Water

We study the structural dynamics of liquid water by time-resolved anisotropic x-ray scattering under

the optical Kerr effect condition. In this way, we can separate the anisotropic scattering decay of 160 fs from

the delayed temperature increase of ∼0.1 K occurring at 1 ps and quantify transient changes in the O-O

pair distribution function. Polarizable molecular dynamics simulations reproduce well the experiment,

indicating transient alignment of molecules along the electric field, which shortens the nearest-neighbor

distances. In addition, analysis of the simulated water local structure provides evidence that two

hypothesized fluctuating water configurations exhibit different polarizability.