Dynamic sound attenuation at hypersonic frequencies in silica glass

TL;DR

This study investigates the mechanisms behind phonon attenuation in silica glass across a wide temperature range, identifying relaxational and anharmonic processes as key contributors to hypersonic sound attenuation.

Contribution

It provides experimental evidence distinguishing between impurity-sensitive relaxational and impurity-insensitive anharmonic attenuation processes in silica glass.

Findings

Low temperature peak linked to relaxational processes and impurities.

High temperature attenuation dominated by anharmonic interactions.

Attenuation behavior varies with OH impurity content.

Abstract

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.