Scaling of β-relaxation in the equilibrium liquid state of sorbitol

The Johari-Goldstein dielectric beta-relaxation has been studied in the molecular liquid, sorbitol. In the narrow temperature interval in which alpha- and beta-relaxation are separated (still being in the equilibrium liquid state), it is shown that beta-relaxation has a temperature-dependence of loss peak frequency and magnitude, which differs from what is found in the glassy state. Within experimental error the beta-peak is "time-temperature invariant" (i.e., shape and loss peak frequency are temperature-independent), while the magnitude increases with temperature following an Arrhenius equation. Finally, for non-equilibrium states we find that loss peak frequency and magnitude show a simple isothermal correlation, which is independent of thermal history. (C) 1998 Elsevier Science B.V. All rights reserved.