Influence of the exchange interaction on quantum beats in the recombination luminescence of radical ion pairs in media of various polarities

An analytical expression for the beat amplitude of recombination luminescence of geminate radical ion pairs in homogeneous solutions is obtained in terms of the step-wise model of the exchange interaction. It is shown that the most effective suppression of the beats amplitude is observed in highly polar media with a weak Coulomb interaction between radical ions. The dephasing effect of a strong exchange interaction in the suppression of the beat amplitude decreases with decreasing polarity of the solvents.