SPIN DYNAMICS AND ELECTRONIC STATES OF N-V CENTERS IN DIAMOND BY EPR AND 4-WAVE-MIXING SPECTROSCOPY

We applied a new phase-modulation technique for nonlinear laser spectroscopy with sub-Hz relative resolving power to measure fundamental relaxation processes of the N-V center in diamond. Complementary EPR experiments versus temperature establish the ground-state spin character in the absence of optical illumination and show that spin-lattice decay occurs via two-phonon processes involving the dominant vibrational mode. The combined results permit deduction of reliable fine-structure assignments for three states of the center and accurate values for zero-field intersystem crossing and spin-lattice relaxation rates from linewidths of individual resonances in the four-wave-mixing spectrum.