PHOTOCHROMIC BEHAVIOR OF THE N3 CENTER IN NEUTRON-IRRADIATED AND ANNEALED TYPE-IB DIAMOND

The absorption strengths of the N3 centres in natural type-Ia and in n eutron-irradiated and post-annealed synthetic type-Ib diamonds have be en measured under various illumination conditions. In the type-Ib diam ond, an increase in absorption is observed during illumination of ligh t with hv greater than or equal to 1.65 eV, a behaviour that is not ob served in type-Ia diamond. The change recovers slowly after the excita tion light is turned off. The phenomena are explained by electron tran sfer between the negative charge state of the N3 centre and electron t raps.