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

It is shown that the stimulated nuclear polarization detected EPR spectra o f spin-correlated radical pairs in high magnetic fields consist of two type s 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 en ergy levels in the rotating frame when the singlet-tripler dynamics in radi cal pairs exhibit peculiar behaviour. The linewidth of holes can be used to determine the mean lifetime of the spin-correlated radical pairs.