Magnetic circular dichroism of the 1.404-eV interstitial nickel absorption transition in high-pressure synthetic diamond

A high-resolution magnetic circular dichroism (MCDA) study of the sharp 1.404-eV zero-phonon absorption line associated with interstitial nickel in high-pressure synthetic diamond is reported. A model is presented attributing the absorption to internal transitions within the 3d(9) configuration of Ni-i(+), as perturbed by the cubic field at the diamond interstitial site, plus a smaller trigonal crystal field. The model provides a consistent explanation of the signs of the circular absorption coefficients of all the observed transitions plus the unusual features of the g values observed for the ground (g(perpendicular to) similar to 0) and excited (g(parallel to) similar to 0) states. A search for an optically detected magnetic resonance in the MCDA was unsuccessful, consistent with the forbidden magnetic resonance transition for an S = 1/2, g(perpendicular to) = 0 ground state. [S0163-1829(99)13231-4].