Recombination yield of geminate radical pairs in high magnetic fields: general results and application to free diffusion Original Research Article

We have derived a general and exact expression for the quantum yield of geminate radical pairs (RPs) in high magnetic fields. We consider the dynamical S–T0 mixing caused by differences in Zeeman and hyperfine interactions, intraradical (T1 and T2) relaxation, and a first-order scavenging process. The recombination process and the exchange interaction are assumed to be isotropic and of the contact type. In order to solve the stochastic Liouville equation, we introduce effective methods to minimize the dimensionality of the problem and to calculate the matrix elements of the superoperators in an arbitrary coupled basis. Our general expression is expressed in terms of the classical Greenʹs function for the relative motion of the radicals, and it is therefore valid for any kind of relative motion. Various limiting cases of the general expression, which are of particular interest, are derived. Explicit analytical formulas for freely diffusing RPs are given, and the high accuracy of the expressions is illustrated by comparison with accurate numerical results.