Nonequilibrium generalization of Forster-Dexter theory for excitation energy transfer

Forster-Dexter theory for excitation energy transfer (EET) is generalized for the account of short time nonequilibrium. kinetics due to the nonstationary bath relaxation. The final rate expression is presented as a spectral overlap between the time dependent stimulated emission and the stationary absorption profiles, which allows experimental determination of the time dependent rate. For a harmonic oscillator bath model, an explicit rate expression is derived and model calculations are performed in order to examine the dependence of the nonequilibrium kinetics on the excitation-bath coupling strength and the temperature. Relevance of the present theory with recent experimental findings and possible future theoretical directions are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.