MANIFESTATION OF QUANTUM COHERENCE UPON RECOMBINATION OF RADICAL-ION PAIRS IN WEAK MAGNETIC-FIELDS - SYSTEMS WITH NONEQUIVALENT 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 solution s. The existence of the local fluorescence maximum in zero field has b een theoretically demonstrated and experimentally verified for radical pairs in which one of the partners contains a great number of non-equ ivalent magnetic nuclei and the local hyperfine fields of the other pa rtner are negligibly small. In terms of a semiclassical approximation, a simple condition for the appearance of the effect has been obtained : Omega tau much greater than 1, where Omega is the effective ESR spe ctrum width and tau is the lifetime of a spin-correlated pair.