Observation of New Short-Wavelength Collective Excitations in Heavy Water by Coherent Inelastic Neutron Scattering

Abstract

A coherent-inelastic-neutron-scattering experiment was performed on liquid ${\mathrm{D}}_{2}$O at room temperature. We observe for the first time the collective high-frequency sound mode as predicted by computer molecular-dynamics simulations. We interpret the excitation to be a mode propagating within the hydrogen-bonded patches existing in liquid water, and distinct from the ordinary sound wave.