Uni-axial stress measurements were made of the 2.242eV photo-induced zero phonon line which was observed in Ni- and N-containing synthetic diamonds after annealing at 1600C. It was shown that the line was an electric dipole transition, which occurred at a defect of rhombic symmetry. The shape of the vibronic sideband and the temperature dependence of the line position and width could be understood by assuming electron–phonon coupling to totally symmetrical vibrational modes which were centered at ħω = 0.055eV. Electron–lattice interactions could not explain the large decrease in zero phonon line intensity with temperature, and it was suggested that a thermally activated de-excitation path was responsible for the observed behavior.

Optical Studies of Nickel Complexes in High Pressure Synthetic Diamond. A.J.Neves, L.Rino, H.Kanda: Diamond and Related Materials, 2003, 12[3-7], 526-30