ANOMALIES IN THE SCALING OF THE DIELECTRIC ALPHA-RELAXATION

By measuring the complex dielectric function over 15 decades in freque ncy we evaluate the scaling of the alpha-relaxation for several glass- forming liquids including propylene carbonate. The temperature depende nce of the mean relaxation time and of the relaxation strength of the relaxation function displays two dynamical regions being separated by a crossover temperature. The observed findings are essentially not in accordance with predictions of the mode-coupling theory and light scat tering results for propylene carbonate [M. Elmroth et al., Phys. Rev. Lett. 68, 79 (1992)].