Practical models for energy transfer between ions in solids

The subject of anomalous energy transfer in solid-state materials is reviewed. Three separate models developed by ourselves and others are presented to describe deviations to the standard Inokuti-Hirayama model of energy transfer between ions in solid-state materials. We've considered the non-random distribution of donors and accepters, new mechanisms of energy transfer for very close donors and accepters, and the spectral discrimination of sub-populations of donors and accepters; all of these affect the observed time-dependent concentrations of excited donors and accepters. Experimental evidence for all of the above in solid-state materials has been presented.