Temporal and polarization characteristics of donor fluorescence in donor-acceptor solid solutions with energy transfer to the acceptors in the ground and triplet states

The influence of Förster resonance energy transfer (FRET) on temporal and polarization characteristics of donor fluorescence was theoretically investigated (by means of Monte-Carlo calculations) in a donor-acceptor solid solution, where acceptor molecules are characterized by the high probability of intersystem crossing (ISC) S1 → T1. It was shown that parameters of the donor fluorescence essentially depend on the ratio between the rate constants of the energy transfer to the acceptor in the ground and triplet states. The values of these constants also determine the temporal changes of the polarization degree of the donor fluorescence as it decays.