Spectral features of the quasielastic line in amorphous solids and supercooled liquids: A detailed low-frequency Raman scattering study

The spectral features of the quasielastic light scattering in amorphous solids and supercooled liquids are investigated through a combined Stokes and antiStokes low-frequency Raman scattering study. Emphasis is given on the specific spectral details of the quasielastic line rather than on elucidating its microscopic origin. Our approach is quite general since it includes glass formers with a strong, an intermediate, and a fragile dynamic character. The results suggest that the quasielastic contribution is a symmetric spectral feature around the laser line. This finding makes possible the separation of the quasielastic line and the Boson peak. It further raises certain skepticism concerning reduction schemes followed up in the literature for the analysis of low-frequency Raman data and for models that combine these two contributions. The limiting (omega --> 0) behavior of the product of the vibrational density of states and the Raman coupling coefficient has also been extracted. The validity of some phenomenological approaches is also discussed in light of the experimental facts presented in this paper and some suggestions are being advanced.