Models for the time development of spectral transfer in disordered systems

The accuracy of models for the time development of the spectral transfer of optical excitation in inhomogeneously broadened systems is assessed. The transfer is assumed to take place on a lattice occupied by a fraction $c$ of optically active ions distributed at random. Symmetric, energy-independent transfer rates which are rapidly decreasing functions of the interion separation are assumed. The distinction is made between low ($c<\mathrm{}0.2\mathrm{}$) and high ($c>\mathrm{}0.5\mathrm{}$) concentration regimes. Appropriate models for three-dimensional systems with short-range transfer are identified for both regimes.