Magnetic field effects in the presence of electrostatic interactions

Magnetic field effects on ion radical pair (IRP) recombination reactions are considered. In the diffusion approximation simple analytical expressions for the magnitudes of these effects are obtained. They are reduced to those obtained within the simple cage approximation in the case, when the intramolecular spin interactions are strong enough and to those obtained within the free radical approximation in the opposite case. The applicability of both simple approximations are shown to be closely connected with peculiarities of the IRP decay kinetics. Namely, the cage approximation is applicable for the strong spin interactions because the IRP decays exponentially at small times. The free radical approximation is valid in the opposite limit of weak interactions since at large times the IRP decays as a free radical pair.