A comparison between acoustic compliance and self-particle susceptibility in associated liquids: The case of water and glycerol

We use Brillouin spectra collected in the visible, ultraviolet and X-ray frequency regions to derive the imaginary part of acoustic compliance, J ''(omega), over an extended frequency range from fractions of GHz to tens of THz. We find that J ''(omega) accurately reproduces the shape of the self-particle susceptibility as determined by incoherent neutron scattering. This analysis is here applied to the case of liquid water in comparison with glycerol, another representative associated liquid, for which the observed correspondence has been proven to imply a close connection between dissipation through acoustic channels and generalized density of states