PAIR-DECAY MODEL OF TIME-DEPENDENT SPECTRAL TRANSFER IN DISORDERED SYSTEMS

A microscopic model is introduced to study the time-dependent spatial diffusion of optical excitations and concomitant spectral transport in inhomogeneously broadened random systems. The optical excitations migrate among a low concentration of optically active impurity ions distributed at random with a site-symmetric transfer rate assumed to be independent of energy mismatch. An explicit analytic calculation is given for dipolar interaction. The result agrees reasonably well with that of a recent Monte Carlo calculation.