Low-frequency light scattering in silica xerogels: influence of the heat treatment

Brillouin and Raman measurements were performed on silica xerogels in a wide range of densities from 0.5 to 2.2 g cm2 and temperatures from 6 to 750 K. The experimental results show that water dynamics gives strong low-frequency Raman scattering and influences the Brillouin shift and attenuation.