The structure of the defect responsible for the H1a absorption feature in diamond was much debated. In this work, the results of uniaxial stress-splitting studies were compared to piezospectroscopic stress-splitting parameters calculated for the ⟨001⟩ dinitrogen split interstitial (N2I) defect. The stress-splitting data showed that the H1a absorption band arose from an A→E transition at a center with D2d symmetry. Furthermore, the experimentally and theoretically determined stress-splitting parameters were in excellent agreement, supporting the assignment of the H1a band to the N2I defect.

Identification of the Dinitrogen ⟨001⟩ Split Interstitial H1a in Diamond. S.Liggins, M.E.Newton, J.P.Goss, P.R.Briddon, D.Fisher: Physical Review B, 2010, 81[8], 085214