Résumé
Physical Review B 73 (2006) 0652201 In order to clarify the origin of the dominant processes responsible for the
acoustic attenuation of phonons, which is a much debatted topic, we present
Bril louin scattering experiments in various silica glasses of different OH
impurities content. A large temperature range, from 5 to 1500 K is
investigated, up to the glass transition temperature. Comparison of the
hypersonic wave attenuation in various samples allows to identify two different
processes. The first one induce s a low temperature peak related to
relaxational processes; it is strongly sensitive to the extrinsic defects. The
second, dominant in the hig h temperature range, is weakly dependent on the
impurities and can be ascribed to anharmonic interactions.