The W27 center was characterized, by means of electron spin resonance, in natural diamond. The center exhibited spin S = 1, a large spin-spin coupling constant (99mT), and a complex hyperfine interaction structure which was interpreted as originating from the interaction of an S = 1 electronic system with five N atoms: 2 of these sites were equivalent and were located near to the S = 1 electrons; 3 others were almost equivalent and more remote. The center was suggested to include a divacancy, where 1 vacancy (bound to two N atoms and one C atom) had trapped an extra electron, while the second vacancy was bound to 3 substitutional N atoms.

Electron Spin Resonance Characterization of a Multi-Nitrogen Complex in Diamond. K.Iakoubovskii, A.Stesmans: Journal of Physics - Condensed Matter, 2002, 14[49], 13679-83