No abstract

Hyperfine interactions associated with the ' N nucleus in the diamond N-V defect have been investigated using Raman-heterodyne techniques. The measured nuclear-magnetic-resonance (NMR) and electron-nuclear-double-resonance frequencies were well accounted for by the triplet-spin Hamiltonian, where all the parameters have been fully determined. Hole-burning effects in electron paramagnetic resonance were observed and the spectral structures are found to be in good agreement with the proposed energy levels. The spin-density distribution in the complex is also discussed. The nuclear dipole moment and NMR homogeneous linewidth have been measured. Optical pumping is also shown to play an important role in determining the hyperfine-transition intensity. Interference measurements in NMR by introducing an additional rf field again indicate that population factors are responsible for the varying Raman-signal amplitudes.

Raman-heterodyne-detected paramagnetic resonance has been used to study the level anticrossing in the 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 Ramanheterodyne-signal intensity. Spin alignment in the 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. This is substantiated by transient nutation and spin-echo measurements, from which the dipole moment and dephasing time are examined. Laser detuning within the 638-nm zero-phonon line shows that the Raman signal is only detectable when the laser frequency is tuned to the low-energy part of the optical line.