Vacuum ultra-violet induced thermoluminescence in γ-irradiated and non-irradiated MgO powder

The effect of γ-irradiation at room temperature on MgO powder samples has been investigated by thermoluminescence (TL) methods. In addition to a TL peak at 516 K, ‘persistent’ changes in the properties of lower temperature TL peaks have been observed in the irradiated samples. This includes mainly an increase in the sensitivity to excitation in the vacuum U.V. region (115-170 nm) as well as the occurrence of TL excitation between 260 and 285 nm, which was hardly observable in the non-irradiated samples. The excitation maximum of the un¬irradiated samples, at 118 nm (10·5 eV) seems to correlate with the prominent absorption peak at 10-8 eV, which has previously been attributed to an interband exciton. The structure in the 160-170 nm range of the excitation spectrum apparently corresponds to the previously reported exciton spectrum. The γ-pre-irradiation also causes a shift of the TL peaks below 350 K towards lower temperatures. The experimental results provide new information regarding the processes involved.