Low-temperature phonon damping in vitreous silica explored by UV Brillouin spectroscopy

The recently developed technique of Brillouin ultraviolet scattering is used to measure phonon dispersion and damping in the prototypical strong glass v-SiO2. Results on the low temperature (T similar to 10-100 K) sound attenuation at a frequency of similar to 66GHz are presented. The comparison between a model, which takes into account dynamical processes (thermally activated relaxations and the interaction with the bath of thermal vibrations), and the experimental data indicates the presence of a strong static contribution in the region explored by Ultraviolet radiation, supporting the presence of a transition between static and dynamic attenuation mechanisms at a frequency of similar to 100GHz.