Dielectric Study on the Johari-Goldstein Mode of Glass-Forming Sorbitol

We investigate precisely the temperature dependence of dielectric relaxations for glass-forming sorbitol, focusing on the Johari-Goldstein (J-G) mode. The results reveal that the relaxation times of the J-G mode exhibit a new dependence at high temperatures, different from the behavior reported at low temperatures so far. As a consequence, it is found that the J-G mode merges smoothly with the α-relaxation mode in the crossover region between the normal liquid and the supercooled one; the branching temperature obtained is much higher than that previously extrapolated from the lower temperature dependence of relaxation times.