Coherent structural relaxation of water from meso- To intermolecular scales measured using neutron spectroscopy with polarization analysis

Abstract

By means of the recent implementation of neutron polarization analysis on a wide-angle time-of-flight spectrometer, we have been able to separately measure coherent and incoherent dynamic structure factors of heavy water with sub-meV resolution in a wide scattering vector (Q) range. The observed decorrelation of collective fluctuations at mesoscales hardly depends on Q. In the crossover towards intermolecular scales, the coherent dynamics is nicely described by the convolution of a Q-independent mode and diffusion, in addition to collective excitations.