Does the Arrhenius Temperature Dependence of the Johari-Goldstein Relaxation Persist above T_g?

Dielectric spectra of the polyalcohols sorbitol and xylitol were measured under isobaric pressures up to 1.8 GPa. At elevated pressure, the separation between the α and β relaxation peaks is larger than at ambient pressure, enabling the β relaxation times to be unambiguously determined. Taking advantage of this, we show that the Arrhenius temperature dependence of the β relaxation time does not persist for temperatures above T_g. This result, consistent with inferences drawn from dielectric relaxation measurements at ambient pressure, is obtained directly, without the usual problematic deconvolution the β and α processes.