RELAXATIONS OF FRAGILE LIQUID BY COMBINATION OF BRILLOUIN TO RAMAN-SCATTERING SPECTRA

The broadband light scattering spectra of glycerol were measured using both the Sandercook-type 3+3 pass vernier tandem Fabry-Perot interfer ometer and the triple-grating additive spectrometer, The depolarized s pectrum at 363 K clearly shows an alpha peak and a boson peak. The lin eshape of spectra was analyzed by the mode coupling theory and from th e phenomenology including an alpha relaxation of Davidson-Cole type an d a bos on peak of the disorder-induced model. In the polarized spectr a, strong coupling between longitudinal acoustic phonon and the fast r elaxation process was observed. It is found that the relaxation freque ncy obtained from the Brillouin components is much higher than that of alpha relaxation, and its temperature dependence is weaker than that of alpha relaxation frequency. This strongly suggests that acoustic ph onons couple not to the alpha but the another fast relaxation process.