The ST_-relaxation mechanism of magnetic field effects on radical pair recombination. Intraradical relaxation versus ST_-relaxation transitions

The nonadiabatic ST_ transition induced by the fluctuating (anistropic) part of the hyperfine and Zeeman interactions are shown to make a significant contribution to the magnetic field effects in the radical pair recombination in liquids and micelles. The anisotropic Zeeman interaction induced ST_ transitions are found to cause a strong decreased in the radical yield Y and strong net electron and nuclear spin polarization at high magnetic field B. The experimentally observed dependence Y(B) is accurately described within the theory developed.