The fast and slow rotation approximations for the description of the kinetics of triplet radical quenching and electron spin polarization

Abstract

The specific features of the mechanisms and kinetics of generation of net chemically induced dynamic electron polarization (CIDEP) in triplet radical quenching (TRQ) in liquids is analysed in detail. The problem reduces to the analysis of fairly strong non-adiabatic transitions between states of the triplet radical spin Hamiltonian which are known to determine CIDEP generation in TRQ. The analysis is performed in two limits of fast and slow rotation of the triplet molecule using the previously developed method of treatment for non-adiabatic transitions. The method made it possible to derive analytical formulas for the CIDEP generation probability P e and rate K e, and for the TRQ probability P q and rate K q in the case of relatively strong quenching. It is shown that the dependence of K e on the relative diffusion coefficient D r is of bell shape and cannot be described correctly by the usually applied relation K e = K q P e.