AN ANALYSIS OF MODELS FOR RESONANT TRANSFER OF EXCITATION USING QUANTUM ELECTRODYNAMICS

The resonance coupling of identical molecules A and B is further explored over all separation distances R. Three models are analyzed. In the first, applicable for short separations, stationary states of the coupled pair are employed. In the second the process is viewed as a time development of \A*B > and the probability of finding the system in \AB* > is calculated. In the third energy transfer is treated as emission followed by absorption. At distances beyond the stationary state regime, where the process is energy transfer from A* to B, we show that the rate calculation must be based on spontaneous emission by A* and absorption by B. Also we note that when some conventional approximations are replaced by a more exact treatment the result appears superficially to be non-causal. However over short times, arguments from time-energy uncertainty indicate that conclusions drawn from attempts to establish causality are difficult to sustain.