Manifestation of quantum coherence upon recombination of radical ion pairs in weak magnetic fields. Systems with non-equivalent nuclei

Magnetosensitive radiofluorescence has been used to study the magnetic field effect at weak magnetic fields during geminate recombination of singlet radical ion pairs formed radiolytically in non-polar solutions. The existence of the local fluorescence maximum in zero field has been theoretically demonstrated and experimentally verified for radical pairs in which one of the partners contains a great number of non-equivalent magnetic nuclei and the local hyperfine fields of the other partner are negligibly small. In terms of a semiclassical approximation, a simple condition for the appearance of the effect has been obtained: Ωτ∗ r > 1, where Ω is the effective ESR spectrum width and T∗ is the lifetime of a spin-correlated pair.