Photon correlation spectroscopy of liquid 2,4-pentanediol near the glass point

Abstract

Photon correlation spectra of neat 2,4-pentanediol and of solutions in CHCl₃ have been obtained in the temperature range between −60 and −30°C. The temperature dependence agrees with dielectric relaxation data and the experimental relaxation times have been fitted to a Vogel-Fulcher-Tamann equation. The width of the distribution of relaxation times is approximately constant over the whole temperature and concentration range. The mean isotropic relaxation time and the mean orientational times derived from the VV and VH correlation functions are nearly equal. The relaxation times have been compared, with the macroscopic shear viscosity by means of the Debye-Stokes-Einstein equation. The main conclusion which is drawn from these findings, in comparison with high temperature interferometric studies published previously, is that two distinct relaxation modes are active and can be distinguished in liquid 2,4-pentanediol.