Abstract
The aim of the study is to determine the mechanism responsible for the high-frequency sound attenuation in glasses. First, we performed Brillouin light scattering experiments in a large temperature range at different frequencies in simple oxide glasses. It is shown in v-B2O3 the difficulty to separate water and annealing effects. In v-GeO2 and v-Li2O-2B2O3 different sound attenuation mechanisms have been identified and their relative importance calculated. Annealing effect in v-GeO2 is also shown. High frequency sound has been observed in v-Li2O-2B2O3 by mean of inelastic x-rays scattering. An anomalous frequency dependence of the attenuation has been observed. It has been attributed to an hybridization of the acoustic waves with low frequency optic-like modes of the glassy matrix. The relation with the low temperature anomalies of glasses is then discussed.