A temperature effect in the luminescence emission from electron-irradiated MgO

Abstract

The temperature dependence of luminescence emissions from electron-irradiated CaO and MgO single crystals has been studied by time resolved luminescence spectroscopy after pulsed nanosecond irradiation with 0.20 to 0.60 MeV electrons. Emissions from CaO at 375 nm at both 293 and 83 K, show similar threshold characteristics for atomic displacement. These have been attributed to the displacement of oxygen ions and subsequent electron trapping, resulting in the formation of F+ centers. The threshold energy of 0.32±0.01 MeV corresponds to an oxygen displacement energy of 58±2 eV. A 380 nm emission from MgO, also attributed to oxygen displacement and F+ center formation, shows no temperature effect, with a displacement threshold virtually identical to that for CaO. A 235 nm emission from MgO shows a significant temperature effect. The threshold energy at 293 K is 0.31±0.01 MeV, whilst at 83 K two thresholds are observed, 0.31±0.01 and 0.41±0.01 MeV.