Delayed fluorescence due to annihilation of triplets produced in recombination of photo-generated ions

In a previous article (J. Chem. Phys. 2002, 116, 2472), the nontrivial viscosity dependence of the geminate recombination efficiency was theoretically studied and briefly shown experimentally. Now, the experiments performed are reported in detail. Furthermore, the multistage kinetics of the fluorescence quenching by electron transfer to impurities is subjected to exhaustive experimental Study and well fitted theoretically using integral encounter theory (IET) of the bimolecular reactions in solution. The quantum yields of free ions and triplet excitations are calculated and their nontrivial viscosity dependence is specified as well as the asymptotics of the bimolecular recombination of both ions and triplets. The annihilation of triplets results in a restoration of sin-let excitations responsible for the delayed fluorescence.