Optically active centers in brown type IaAB diamonds from the Istok placer in the northeastern Siberian Platform: spectroscopic properties and the effect of HPHT treatment

In this work, step-by-step high-pressure high-temperature annealing of plastically deformed-type IaAB diamonds from the Istok placer has been performed and the behavior of characteristic centers has been investigated by infrared, electron paramagnetic resonance, and photoluminescence spectroscopies. A new paramagnetic center with one magnetically inequivalent position and hyperfine structure from one hydrogen atom has been found. This paramagnetic center can be assigned to the dangling carbon bond in the dislocation core, and the hydrogen hyperfine structure is due to the polarization of the electron shell of hydrogen forming the C–H bond. For this center and W7 center, the annealing temperatures have been determined. Spin relaxation was studied by pulse electron paramagnetic resonance technique at low temperatures. The spin–spin relaxation times for the W7 and 490.7 centers exclude exchange interactions between the paramagnetic centers. At the same time, the close spin–lattice relaxation times for these centers can be determined by the distorted structure near the dislocation core.