Integral encounter theories of multistage reactions. II. Reversible inter-molecular energy transfer

The matrix Modified Encounter Theory (MET), developed in Part I of this wor k, is applied here to reversible inter-molecular energy transfer in liquid solutions. For fluorescence quantum yield at contact transfer the Stern-Vol mer law is confirmed, but the concentration corrections to its constant are diffusion-dependent unlike those obtained earlier with Superposition Appro ximation. In the particular case of irreversible energy transfer, when the exact solution is available, the latter is used to discriminate between all competing approaches and establishes MET superiority. In the case of rever sible energy transfer producing the long-lived or even stable products, the energy is stored there and dissipates due to backward energy transfer in r e-encounters. The kinetics of this process, resulting in a delayed fluoresc ence, is shown to be qualitatively different in cases of short and long enc ounter times as compared to the excitation lifetime. (C) 2001 American Inst itute;of Physics.