Brillouin scattering on the glass former GeSBr2

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Abstract
Brillouin scattering measurements were performed on the partly interrupted network glass former GeSBr2. Spectra were taken in symmetrical transmission arrangement, and in backscattering, thus varying momentum transfer between 2×104/cm and 44×104/cm. The temperature range was −100 °C<TTg∼−30 °C. The Brillouin spectra were carefully compared with viscoelastic theory. Strong relaxation accompanied by a dispersion of sound velocity occurs between 100 and 200 °C. A comparison of the spectra taken at different scattering angles and temperatures constitutes convincing evidence for a distribution of relaxation times (a Cole–Davidson distribution is used). The temperature dependence of the maximum relaxation time τ0 can well be described as Arrhenius‐like, τ0 varying from 10−11 to>5×10−9 s. The temperature dependences of the high frequency and the adiabatic sound velocities are derived. From the q‐dependence, a fast relaxation channel can be identified. We discuss the assumption that it is directly connected with the break up of the glass above Tg. Including this term an agreement is reached between experiment and viscoelastic theory on the level of about 1% for the Brillouin line position and of about 10% for the linewidths, for the glassy, highly viscous, and (relatively) low viscosity regime.