Zero-phonon linewidth of single nitrogen vacancy centers in diamond nanocrystals

Photoluminescence excitation spectroscopy of nitrogen vacancy (NV) centers in type Ib diamond nanocrystals shows that in spite of spectral diffusion and spin-nonconserving transitions, zero-phonon linewidth as small as 160.3em0exMHz, which is nearly lifetime limited, can be observed at low temperature. Relatively small effects of spectral diffusion have also been observed in a small fraction of NV centers.