Excitation and decay of H4 luminescence in diamond

Abstract

Photoluminescence and cathodoluminescence decay time measurements have been carried out for the H4 (2.499 eV) centre in diamond. The photoluminescence decay time increases progressively from approximately= 19 to 23 ns as the energy of the exciting light is increased from 2.6 to 4.0 eV, and the cathodoluminescence decay curves are non-exponential. Luminescence excitation measurements reveal a previously unreported absorption band peaking at about 3.2 eV in the ultraviolet spectral region; absorption of light in this band produces H4 luminescence. The range of decay times noted above is believed to be due, at least in part, to transitions from the higher excited levels via the 2.499 eV excited state. The decay time of 19+or-1 ns measured with photoexcitation at 2.6 eV shows no significant variation with temperature, and this represents the most likely value of the radiative lifetime of the 2.499 eV centre.