Sound attenuation in an 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 wavevector q values of 0.075 nm^{-1}, as a function of temperature. The measured attenuation scales on visible data following a q^2 behavior and is temperature-dependent. Such temperature dependence is found in a good agreement with that measured at lower q, suggesting that its origin is mainly due to a dynamic attenuation mechanism. The comparison between the present data with those obtained by Inelastic X-ray Scattering suggests the existence of a cross-over to a different attenuation regimes.