New data on the nature of the EPR OK1 and N3 centers in diamond

The well-known diamond electron paramagnetic resonance (EPR) OK1 and N3 defects are discussed in the context of incorporation of heavy metal, supposedly Ti, in the double semivacancy and substitutional structures, respectively. X-ray phase analysis of inclusions of the growth medium, eclogite, in the diamonds under study shows an atypically high concentration of titanium compounds. To support proposed models, the hyperfine structure (HFS) from ¹³C in the OK1 center has been analyzed more precisely. The data obtained are consistent with attributing additional satellites around the main EPR lines to HFS from ⁴⁷Ti and ⁴⁹Ti. A double semivacancy model describes the directions of g and A tensor components of the OK1 center. The features of infrared and photoluminescence spectra related to the OK1/S1 and N3/440.3 nm centers are presented.