Vibronic spectra in diamond

The temperature dependence of some of the more important vibronic bands in diamond is investigated. Spectra of the N3, ND1, 640 nm, H3, 3.188 eV and 594 nm bands are given, together with detailed measurements of the intensity, peak energy and width of most of the zero phonon lines over the temperature range of typically 20 to 350K. These data, and published data on the N9 band, are analysed in terms of coupling of the electrons to vibrational modes that are totally symmetric in the point group of the optical centres. It is shown that the shapes of the N3, ND1, 640 nm, 3.188 eV, 594 nm and N9 bands may be closely described by the theory and yield effective densities of coupled phonon states. These densities of states predict, to a high accuracy, the temperature dependence of the respective zero phonon intensities. It is shown that the long-wavelength modes dominate the temperature dependence of the zero phonon energy, and so, after allowing for lattice expansion effects, the peak energy may be fitted using the densities of states.