SUBENSEMBLES AND KOHLRAUSCH RELAXATION IN ELECTRONIC AND MOLECULAR GLASSES

A new theory of glassy relaxation has recently identified two intrinsi c stretched exponential relaxation channels associated with charge and density fluctuations characterized by two magic stretching fractions, beta(c) = beta(K) = 3/7 and beta(d) = beta(sr) = 3/5. The theory is r evised here to describe structural relaxation in the presence of defec ts such as kinks in polymers. The revised theory explains recent NMR m ultiple-spin-echo experiments which exhibit two corresponding relaxati on modes ('slow' and 'fast'). A remarkable byproduct of the theory is an explanation of the origin of the Vogel-Fulcher 'singularity' in the viscosity of fragile glass formers near the glass transition as the r esult of two-stage structural arrest.