8-SCATTERING STUDY OF BETA-RELAXATION IN CAKNO3 AND SALOL NEAR THE LIQUID-GLASS TRANSITION - IDEALIZED AND EXTENDED MODE-COUPLING THEORY ANALYSIS

Depolarized light-scattering measurements have revealed the dynamics o f CaKNO3 and salol near their liquid-glass transition temperatures in the frequency range of similar to 0.2 GHz to similar to 4 THz. The two -step relaxation process predicted by the mode coupling theory was obs erved in the supercooled liquid near T-c. Idealized mode coupling theo ry analysis for the beta-relaxation region provided reasonable agreeme nt with the scaling predictions. The crossover temperature was identif ied from both above and below T-c. However, systematic differences bet ween the experimental data and the idealized theoretical beta-spectra were observed at low frequencies for temperatures near and below T-c. An extended mode coupling theory analysis, which includes the phonon-a ssisted hopping transport, provided a good description of the complete experimental beta-spectra. The hopping rate was quantitatively estima ted from the analysis. Transition regions and trajectories were found in the temperature-hopping rate plane.