Physical Review
Decay Modes with Coherent Resonant-Energy Transfer between Deep Impurities in Solids
Russell C. Casella
Abstract
Attention is called to the existence of new decay modes for deep impurities in solids associated with coherence in the resonant-energy transfer between them. The theoretical decay rate $R$ of the two-impurity complex is of the form $R(t)={C}_{1}\mathrm{exp}(\ensuremath{-}{\ensuremath{\gamma}}_{1}t)+{C}_{2}\mathrm{exp}(\ensuremath{-}{\ensuremath{\gamma}}_{2}t)+\mathrm{exp}[\ensuremath{-}\frac{1}{2}({\ensuremath{\gamma}}_{1}+{\ensuremath{\gamma}}_{2})t]\ifmmode\times\else\texttimes\fi{}\mathrm{Re}D\mathrm{exp}(\ensuremath{-}i\ensuremath{\Delta}t)$, with ${C}_{n}$, ${\ensuremath{\gamma}}_{n}$ real positive, $\ensuremath{\Delta}$ real, and $D$ complex. The oscillations in time $t$ exhibited by the third term in the expression for $R$ provide an experimental test for the coherence effect. The partial rate ${R}_{\ensuremath{\nu}}(t)$ for radiative decay is of the same form as the total rate $R(t)$. In the analysis, use is made of an analogy between the decay of the excited impurity complex and that of ${K}^{0}$ mesons in particle physics, where similar coherent oscillations have been observed experimentally.