A new approach to radiationless decay phenomena by generalization of the Mori theory

A suitable extension of the Mori theory to deal with non-hermitian hamiltonians leads to a rigorous justification of models of “reduced” kind for radiationless decay phenomena. By using the model of an excited state sequentially coupled to two dissipative quasicontinua it is shown that the generalized theory leads to a reduced model consisting of only two “virtual” states. The standard Mori approach, on the contrary, would result in a chain of more than two states (probably an infinite number of states). It is shown, furthermore, that the biexponential decay behaviour can rigorously be justified in two different ways. The first model only consisists ofcouplings of intramolecular type. The second model also involves an external thermal bath. The generalized Mori theory, when applied to the second model leads to a non phenomenological justification for the kinetic scheme. It is shown, furthermore, that excitations by strong radiation fields result in a different decay behaviour according to whether the former or the latter scheme is applied.