Twelve satellite centres, labelled as R1A-L, were detected and characterised by electron spin resonance around the R1 centre, which was previously identified with the di-interstitial in diamond. The R1 satellites exhibit spin S = 1 and monoclinic-I symmetry; their spin-spin interaction constant D was up to 4% smaller, but the anisotropy parameter E was significantly larger than that of the R1 centre. All the satellites annealed out at 300 to 350C, which was slightly lower than that of the R1 centre. However, the R1 centre, but not its satellites, could be restored by UV illumination after annealing at up to 800C. The experimental observations could be accounted for by a model assigning the R1A-L centres to distinct pairs of a di-interstitial and a neutral vacancy located in the {110} symmetry plane of the di-interstitial.

Electron Spin Resonance Study of Perturbed Di-Interstitials in Diamond. K.Iakoubovskii, J.M.Baker, M.E.Newton: Physica Status Solidi A, 2004, 201[11], 2516-20