Mariana I. Rakhmanova

Distribution of OK1, N3 and NU1 defects in diamond crystals of different habits

Comprehensive studies of diamond crystals with a low nitrogen concentration from the placer deposits and kimberlite pipes of Yakutia have facilitated the detection of three titanium-nitrogen-related centers: OK1/S1, N3/440.3 nm and NU1/485 nm in the EPR and photoluminescence spectra. Additional proof of titanium presence in the structure of EPR N3 center was obtained from the hyperfine structure of titanium magnetic isotopes 47 Ti and 49 Ti. Titanium-nitrogen-related centers in the neighboring substitutional sites (N3/440.3 nm) and in the structure of the interstitial (NU1/485 nm) are not found in cubic habit crystals, which are characterized by the presence of the OK1/S1 center with a double semi-vacancy structure. All three types of nitrogen-titanium-related centers are present in cuboctahedral habit diamonds. It is assumed that these habit-specific distributions of defects in diamond are a result of the peculiarities of incorporating nitrogen and titanium impurities into the different growth sector of crystals and aggregation thereof at high pressure and temperature.

Impurity centers in synthetic and natural diamonds with a system of electron-vibronic Lines at 418 nm in luminescence spectra

Analysis of the spectra of IR absorption, ESR, and luminescence of natural and synthetic diamonds with a system of electron-vibronic lines at 418 nm in the luminescence spectrum showed the participation of nickel ions in the formation of these centers. It was assumed that the system of lines at 418 nm is the manifestation of the nickel-containing NIRIM5 center. The nature of the NIRIM5 center was discussed.