Nickel-nitrogen complexes in synthetic diamond: the 2.429 eV absorption system

We report the effects of applied uniaxial stresses on this system as well as the temperature dependence of the ZPL. It is shown that stress dependence of both the ZPL and the one-phonon line (OPL) can be understood in terms of an electric dipole transition occurring at a rhombic I centre. The temperature dependence of the 2.429 eV ZPL line and the shape of the vibronic sideband can be explained assuming electron-phonon coupling to a totally symmetric vibrational single mode at ħω=49 meV. The relation between this system and the photo luminescence (PL) centre with ZPL at 1.660 eV was also analysed and, in disagreement with a previously proposed model, we conclude that the observed transitions do not occur at the same centre.