Comment on a shape of EPR spectra of spin-correlated radical pairs and separate radicals escaped geminate recombination

For model spin-correlated radical pairs (RPs) the EPR spectra are simulated and their shape is analyzed in detail. It is demonstrated that the widths and intensities of the EPR spectra are determined essentially by the rate of the singlet-triplet dephasing and the scale of the spin-spin interactions. It is also shown that chemical exchange of the RPs between states with different values of the exchange and the dipole-dipole interactions can produce the apparent antiphase structure lines in the EPR spectra.