Calculation of triplet-singlet transition efficiencies controlled by relative rotational diffusion of the two constituents of covalently linked radical pairs Original Research Article

We present a model by which the efficiency of T0-S and T−1-S mixing in a polyphyrin-quinone radical pair can be calculated. Rotational diffusion of the quinone relative to the porphyrin, causing a stochastic modulation of the exchange integral J, is included and contributes to the efficiency of triplet-singlet mixing. The model calculations can reproduce the mixing efficiencies extracted from time-resolved X-band EPR measurements.