Brillouin Scattering Study of Glass-Forming Propylene Glycol

Brillouin scattering of hypersonic sound waves by fragile glass-forming propylene glycol has been studied using a (3+3)-pass vernier tandem Fabry-Perot interferometer at temperatures between 364K and 140 K. The velocity dispersion has been analyzed using the Cole-Davidson model (β CD = 0.45). The relaxation time was found to obey the Arrhenius law, and we have obtained AE = 0.28eV and τ o = 1.26 x 10 -15 s. The relaxation strength (or the Debye-Waller factor in the mode coupling theory (MCT)) was found to obey the (T c - T) 1/2 law below T c = 314 K, as predicted by the MCT. However the crossover temperature T c was much higher than our previous result of T c = 227 ± 5 K which was obtained from the broadband susceptibility spectra.