Zero-Phonon Lines and Phonon Coupling in Neutron Irradiated MgO Crystals

Abstract

Color centers and zero-phonon lines due to impurities or lattice defects in MgO single crystals irradiated in a reactor at 80°K are reported. A number of sharp absorption bands have been interpreted as a single phonon band and/or two-phonon combination bands involving several characteristic phonon energies. Four characteristics of the zero-phonon lines are investigated experimentally as functions of the temperature; namely, the ratios of the line intensities to their associated broad bands, the shift in the peak position, the half-width and the line shape. The results can be well described in terms of Raman scattering of Debye-model phonons, although different Debye temperatures must be assigned to different zero-phonon lines.