New EPR spectra in diamonds with a high concentration of nitrogen atoms

The EPR spectrum of a synthetic diamond, containing a high concentration of isolated substitutional nitrogen, N-S (the P1 EPR centre), shows in additi on to the spectrum of P1 three other features not previously observed in ni trogen containing diamond: 1. an 'allowed' pair spectrum close to that of P1 corresponding to interact ing pairs of N-S at three sites separated by 0.357-0.564 nm; 2. a 'forbidden' pair spectrum at about half of the magnetic field required for P1, with hyperfine structure characteristic of a pair of interacting n uclei with I = 1, each with the same hyperfine parameters as P1: correspond ing to a superposition of many pairs of separation greater than 0.7 nm; 3. a double quantum spectrum of P1, being an exact replica of the normal sp ectrum at twice the magnetic field. (C) 1999 Elsevier Science S.A. All righ ts reserved.