4 - Exciton transfer rates and hopping dynamics

Abstract

The transfer of excitons between weakly coupled chromophores or groups of them can be represented by rate process. This chapter provides detailed theoretical account of how such rate equations can be derived based on Fermi golden rule. Between localized excitons with constant electronic couplings, this leads to well-known theories developed by Förster and Dexter long time ago. For the case where the electronic coupling depends on nuclear or bath degrees of freedom, a rate expression accounting for inelastic effect can be obtained. Between groups of chromophores, a rate expression generalizing Förster's spectral overlap expression for multichromophoric case is obtained. This rate expression can be used to describe the transfer of delocalized excitons for a broad range of systems. The chapter also provides a brief review of master equation approaches for hopping dynamics where the rate equations are employed as transition probabilities for population transfer.