Light scattering spectra of fast relaxation in silica and ${\mathrm{Ca}}_{0.4}{\mathrm{K}}_{0.6}({\mathrm{NO}}_3{)}_{1.4}$ glasses

Light-scattering spectra of two glasses, ${\mathrm{Ca}}_{0.4}{\mathrm{K}}_{0.6}({\mathrm{NO}}_3{)}_{1.4}$ and silica are measured in the frequency range $1–10000\hspace{0.5em}\mathrm{GHz},$ covering temperatures from 19 K to 310 K. The low-frequency wing of the fast-relaxation spectrum is found to show a power-law behavior with an exponent $\alpha$ proportional to temperature at values α<0.7. The data are qualitatively and quantitatively compared to different models on relaxations in glasses. It is shown that a model of thermally activated transitions in double-well potentials well describes the fast-relaxation spectra in both materials.