Key points are not available for this paper at this time.
High-resolution, inelastic x-ray scattering measurements of the dynamic structure factor S (q, ) of liquid water in the THz frequency range have been performed as a function of wave vector q (1--7 nm^-1) and temperature T (273--473 K), using pressure (0--1. 5 kbar) to keep the density at 1 g/cm^3. We show that, for q2 nm^-1, we find that the viscoelastic contribution to the memory function becomes q dependent. Thus this work provides a view on the evolution of the collective dynamics of water across the q region where the continuum approximation inherent in the hydrodynamic formulation begins to fail. The physical consequences of such a result are discussed in some detail.
Monaco et al. (Mon,) studied this question.