Complex permittivity was obtained on glycerol, xylitol, sorbitol and sorbitol-xylitol mixtures in the supercooled liquid state in the frequency range between $10\mu \mathrm{}\mathrm{Hz}$ and $500\mathrm{MHz}$ at temperatures near and above the glass transition temperature. For all the materials, a dielectric relaxation process was observed in addition to the well-known structural $\alpha$ and Johari-Goldstein $\beta$ relaxation process [G. P. Johari and M. Goldstein, J. Chem. Phys. 53, 2372 (1970)]. The relaxation time for the new process is always larger than that for the $\alpha$ process. The relaxation time shows non-Arrhenius temperature dependence with correlation to the behavior of the $\alpha$ process and it depends on the molecular size systematically. The dielectric relaxation strength for the new process shows the effect of thermal history and decreases exponentially with time at a constant temperature. It can be considered that a nonequilibrium dynamics causes the new process.

• Received 24 October 2005

DOI:https://doi.org/10.1103/PhysRevE.73.041510