The thermoluminescence of CaO and CaO-Bi monocrystals which had been vacuum ultra-violet irradiated at 80K, or X-irradiated at 4.2K, was reported. By varying the energy of the ultra-violet irradiation, the creation spectra of various peaks were determined. From analyses of these spectra it was concluded that, in the excitation spectrum of CaO, indirect transitions could already begin to play an important role at 6.5eV. Long-lived phosphorescence, as well as low-temperature thermoluminescence peaks at 20, 37, and about 50K, were observed in X-irradiated CaO and CaO-Bi monocrystals. This phosphorescence was interpreted in terms of tunnelling recombination between holes and electrons which were trapped by cation vacancies (V centers) and unidentified donor centers, respectively. Thermal destruction of the latter occurred at about 50K.

S.A.Dolgov, T.Kärner, A.Maaroos, T.I.Savikhina, E.A.Vasilchenko: Physica Status Solidi B, 1994, 186[2], 581-90