Sound attenuation in a unexplored frequency region: Brillouin ultraviolet light scattering measurements in v-SiO2

We report ultraviolet Brillouin light-scattering experimental data on V-SiO2 in an unexplored frequency region, performed with a newly available spectrometer, up to exchanged wave vector q values of 0.075 nm(-1), at different temperatures. The measured attenuation follows a q(2) law and is temperature dependent. Such temperature dependence is found to be in good agreement with that measured at lower q, suggesting that the broadening of the Brillouin peak is mainly due to a dynamic attenuation mechanism. The comparison of the present data with those obtained by inelastic x-ray and visible scattering indicates the existence of a crossover among different attenuation mechanisms, whose nature is briefly discussed.