Spectral Shape of Relaxations in Silica Glass

TL;DR

This study presents detailed low-frequency light scattering measurements on silica glass, revealing a power-law spectral shape of relaxations that varies with temperature and spans over nine orders of magnitude in frequency.

Contribution

It provides the first observation of the spectral shape of relaxations in silica glass across a broad frequency range, supporting a thermally activated transition model.

Findings

Spectral shape shows a power-law low-frequency wing with an exponent proportional to temperature.

Relaxations in silica are consistent with thermally activated transitions in double well potentials.

Power-law behavior describes relaxations over nine orders of magnitude in frequency.

Abstract

Precise low-frequency light scattering experiments on silica glass are presented, covering a broad temperature and frequency range (9 GHz < \nu < 2 THz). For the first time the spectral shape of relaxations is observed over more than one decade in frequency. The spectra show a power-law low-frequency wing of the relaxational part of the spectrum with an exponent $\alpha $ proportional to temperature in the range 30 K < T < 200 K. A comparison of our results with those from acoustic attenuation experiments performed at different frequencies shows that this power-law behaviour rather well describes relaxations in silica over 9 orders of magnitude in frequency. These findings can be explained by a model of thermally activated transitions in double well potentials.