Cros-relaxation of localized triplet states in diamond

We have performed optically detected spin coherent transient measurements for two distinct localized triplet states in brown colored diamond. The triplet states of interest belong to the N?V center in its ground state and the V?O (or 2.818 eV) center in its photo-excited phosphorescent state, respectively. In this paper we focus on the dynamics of cross-relaxation processes which occur when small magnetic fields are applied in such a way that the defect triplet states of the probed centers are tuned in resonance with other defects in the lattice of different spin temperature. The coherent transients reveal the dynamics of cross-relaxation and pure dephasing processes. A quantitative analysis shows that the observed cross-relaxation arises from magnetic dipolar interactions between the probed defects and randomly distributed other defects in the lattice.