Models for energy transfer in solids

Two new approaches for describing the dynamics of energy transfer in solids have been developed and are described here. The first is a method for treating the case in which weak direct sensitizer-activator interaction acts as a small perturbation on energy transfer by diffusion among sensitizers. A technique involving a propagator expansion and the Born approximation in the interaction strength is used to solve this problem. The second approach is a Monte Carlo technique to simulate the migration of energy on a random distribution of sensitizers. The predictions of both these models are compared to experimental results and to the predictions of other theoretical models. In their regions of validity they predict significantly different results than those of the models commonly used. The models developed here are applicable to many important materials such as those used for rare-earth lasers.