Paramagnetic resonance of photoexcited N-V defects in diamond. I. Level anticrossing in the 3A ground state.

Raman-heterodyne-detected paramagnetic resonance has been used to study the level anticrossing in the 3 A state of the N-V defect in diamond. The electron-paramagnetic-resonance (EPR) frequencies are well accounted for by a triplet-spin Hamiltonian. Comparison of the EPR spectra with the calculated transition dipole strengths indicates that optical pumping determines, to a large extent, the Raman-heterodyne-signal intensity. Spin alignment in the 3 A ground state under optical pumping leads to the collapse of the EPR signal at the level anticrossing, where the population is equalized due to the mixing of the spin states