Excited levels of the 2.56 eV emission in synthetic diamond

Abstract

The 2.56 eV luminescence is found in high pressure synthetic diamond grown in the presence of the Ni-Fe catalyst and presents a multiplet zero phonon line structure. The vibronic analysis of the band using the linear electron-phonon coupling model indicates that the lower energy component of the zero phonon line structure couples preferentially to a near local phonon of 21 meV, while the other components present among themselves a similar vibronic coupling with a weaker coupling to the 21 meV mode. The further splitting that some components present is shown to be due to ground state splitting. These results suggest that the luminescence is due to emission from two electronic levels one of them split in four components to a doubly split ground state. The nature of the centre is discussed.