Quantum-chemical theory of electronic excitation energy transfer in molecular systems

The approach to describing energy transfer suggested by Forster is critical ly analyzed in the context of the present-day views on nonradiative transit ions. The main presumptions of the Forster theory are shown to be erroneous , A new variant of the theory of electronic energy transfer based on the th eory of electronic transitions is suggested. It is assumed that intermolecu lar interactions between donor and acceptor molecules perturb the electroni c states of isolated molecules prior to donor molecule excitation. A charac teristic feature of intermolecular interactions is spatial delocalization o f the wave functions of interacting molecule electronic states. As a result , usual photophysical processes involving electronic states of different mo lecules may occur in bimolecular systems. Experimentally, nonradiative inte rmolecular transition consequences are observed as evidence of electronic e xcitation energy transfer from donor to acceptor molecules.