Phonon-Assisted Optical Absorption in Irradiated MgO

Abstract

Color centers are introduced into MgO single crystals by reactor neutron irradiations. The energy separations obtained from several sharp peaks appeared on longer wavelength tail of 352 and 980 nm bands are in good agreement with characteristic phonon energies calculated by Karo and Hardy. The identifications of both 352 and 980 nm bands are considered: It is suggested to assign the 352 nm band to the Cr ion centers associated with a certain vacancies or defects and the 980 nm band to the M′ centers.