Composite structure of the stimulated nuclear polarization detected electron paramagnetic resonance spectra of the spin-correlated radical pairs in high magnetic fields

Abstract

It is shown that the stimulated nuclear polarization detected EPR spectra of spin-correlated radical pairs in high magnetic fields consist of two types of component. There are lines which correspond to hyperfine components of the EPR spectra of radical pairs. In addition, narrow holes are expected. Their physical origin is degeneracy or avoided level crossing of the two energy levels in the rotating frame when the singlet-triplet dynamics in radical pairs exhibit peculiar behaviour. The linewidth of holes can be used to determine the mean lifetime of the spin-correlated radical pairs.