Irradiation damage in single crystals of magnesium oxide

Abstract

Single crystals of magnesium oxide have been subjected to ultra-violet x and neutron irradiation. The bands produced by these radiations, their optical and thermal bleaching and associated luminescence are discussed. Taking into account the data of other workers, schemes for ultra-violet activation and luminescence are proposed. The ultra-violet, activation is attributed to the freeing of positive holes, perhaps with exciton formation m an intermediary process, and the subsequent trapping of both electrons and positive holes at negative and positive ion vacancies. The role of the various impurities is discussed and it is concluded that they do not directly give rise to the optical absorption bands observed. The luminescence scheme assumes an optical band width of over 7.0 ev. It is then shown that the various luminescence photon energies correspond to values which are to be expected on the assumption that the optical absorption energies represent the heights of bands measured from the top of the valence band.