The role of 14N and 13C hyperfine structure in characterizing point defects in diamond

Hyperfine structure (hfs), of either C-13 or N-14, observed in the electron paramagnetic resonance (EPR) spectrum, has been a remarkably powerful indicator of the models of paramagnetic defects in diamond. It has often been valuable or necessary to use the much higher resolution of electron nuclear double resonance (ENDOR). Measurements of hfs have recently allowed considerable progress in understanding the nature of defects which have been uncharacterized for many years. A rich variety of defects involving up to at least N-14 atoms, which readily substitute for C atoms, has been found in diamond. The role of 14N hfs is reviewed in solving problems where different aspects are relevant. The use of synthetic diamond, enriched by up to 10% in C-13, has greatly facilitated the construction of models for centres produced by radiation damage, where the only information is from C-13 hfs. Both N-14 and C-13 hfs have confirmed models of Ni related centres.