Carbon isotope substitution and quasi-intersection of energy levels in diamond
The paper presents the results of a study of spin States in the main electronic state of the only nitrogen-vacancy center (NV–) in a 13C-enriched diamond. The analysis is based on applying a method that uses a full set of commuting operators. The results show that there are two double degenerations of energy levels in this system, which can be considered as a special case of LAC. Changes in the properties of the spin States of the NV–-center at the quasi-intersection level are considered as a possible cause of changes in the photoluminescence intensity of NV–-centers.