Light scattering of supercooled propylene glycol

Abstract

The broadband light scattering spectra of propylene glycol were studied by using a Sandercook-type 3 + 3-pass tandem Fabry - Pérot interferometer and a triple-grating spectrometer. The depolarized spectrum in the liquid phase at 363 K clearly shows an peak and a boson peak, and the former peak becomes lower remarkably on cooling. The line shape of the spectra was analysed by the superposition of relaxation of Davidson - Cole type, a fast relaxation of Debye type and a boson peak. Although the fast relaxation time is temperature independent, its intensity tends to zero at 140 K. Another fast relaxation process was also observed by the Brillouin components of the polarized spectra. Its relaxation time is between the -relaxation time and the fast relaxation time and obeys an Arrhenius law.