Density functional theory was used to investigate the optical properties of vacancy di-nitrogen, vacancy–nitrogen–hydrogen and vacancy di-hydrogen defects. The first was a common defect found in irradiated natural type IaA diamonds while the second was found in as-grown CVD diamond. The last had not yet been detected. It was found that these defects possessed at least two charge states which could lead to photochromic behaviour. In the neutral and negative states, the three defects had optical bands due to internal transitions and two weaker optical absorption bands coming from charge state changes. Thus at least four absorption bands were expected for these defects. Vibrational modes of the hydrogen defects were reported.

Optically Active Point Defects in High Quality Single Crystal Diamond. J.P.Goss, P.R.Briddon, H.Pinto, R.Jones: Physica Status Solidi A, 2010, 207[9], 2049–53