Hyperfine interaction in the ground state of the negatively charged nitrogen vacancy center in diamond

The (14)N, (15)N, and (13)C hyperfine interactions in the ground state of the negatively charged nitrogen vacancy (NV(-)) center have been investigated using electron-paramagnetic-resonance spectroscopy. The previously published parameters for the (14)N hyperfine interaction do not produce a satisfactory fit to the experimental NV(-) electron-paramagnetic-resonance data. The small anisotropic component of the NV(-) hyperfine interaction can be explained from dipolar interaction between the nitrogen nucleus and the unpaired-electron probability density localized on the three carbon atoms neighboring the vacancy. Optical spin polarization of the NV(-) ground state was used to enhance the electron-paramagnetic-resonance sensitivity enabling detailed study of the hyperfine interaction with (13)C neighbors. The data confirmed the identification of three equivalent carbon nearest neighbors but indicated the next largest (13)C interaction is with six, rather than as previously assumed three, equivalent neighboring carbon atoms.