The optical transitions at the single substitutional N centre, P1, in synthetic diamond were considered. It was shown that the 4.6eV absorption band was not due to P1, but to some other centre. This was tentatively suggested to be a N-B complex. The 4.5eV photo-current threshold was attributed to a transition from the valence band to the ground state of the P1 centre.

Optical Transitions at the Substitutional Nitrogen Centre in Diamond. K.Iakoubovskii, G.J.Adriaenssens: Journal of Physics - Condensed Matter, 2000, 12[6], L77-81