The 'H2' optical transition in diamond: The effects of uniaxial stress perturbations, temperature and isotopic substitution

Abstract

Uniaxial stress perturbations establish the 1.257 eV 'H2' zero-phonon line as an electric-dipole allowed transition at the centre of a C2v point group. Taken in conjunction with a simple one-electron model, the magnitudes of the perturbations support recent suggestions that the H2 centre is a negative charge state of the well-known nitrogen-vacancy-nitrogen 'H3' centre. The H2 zero-phonon line is 0.9 meV higher in energy in 13C diamond than in 12C diamond. The shift is consistent, within large uncertainties, with the shift expected from the temperature dependence of the line. A local vibrational mode involving predominantly carbon atoms is identified.