Merging of alpha and slow beta relaxation in supercooled liquids.

Dielectric relaxation spectroscopy (1 Hz - 20 GHz) has been performed on supercooled glass-formers from the temperature of glass transition (T(g)) up to that of melting. Precise measurements particularly in the frequencies of MHz order have revealed that the temperature dependences of secondary beta relaxation times in well above T(g) deviate from the Arrhenius relation below T(g): the beta process does not merge with the alpha process around the dynamical crossover temperature in contradiction to previously speculated extrapolations.