The quenching of fluorescence by reversible bimolecular ionization, followed by reversible exciplex formation from an ion pair (Scheme II) subjected to spin-conversion and subsequent radical-ion recombination/separation, has been studied by means of integral encounter theory (IET) and fitted to the available experimental data. Using the incoherent (rate) model of spin-conversion, the ion recombination to the excited triplet products is also accounted for. All of the results are obtained and shown to be different for the pulse excitation of fluorescence and its stationary detection. The free-energy dependence of all of the calculated properties of the forward and backward electron transfer are specified and compared with the conventional free-energy gap (FEG) law.
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