Nonequilibrium generalization of Fo¨rster–Dexter theory for excitation energy transfer

Fo¨rster–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. [Copyright &y& Elsevier]