Phys.org August 25, 2021
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. An international team of researchers (USA – SLAC National Accelerator Laboratory, UC Davis, University of Nebraska, Stanford University, Sweden) measured 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. They observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations revealed the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Their experiment and simulations unveiled the intermolecular character of the water vibration preceding the relaxation of the OH stretch…read more. TECHNICAL ARTICLE
Experiment overview. Credit: Nature volume 596, pages531–535 (2021)