Thermoluminescent mechanisms involving transition metal ion impurities and V-type centres in MgO crystals exposed to ultraviolet radiation

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Thermoluminescent (TL) mechanisms involving Fe, Cr, Mn and V ions in both divalent and trivalent valence states, and V-type centres were studied in MgO single crystals of varying impurity content after exposure to ultraviolet radiation. Using the ESR technique, it is shown that samples containing primarily divalent impurities show no V-type centres related to the TL mechanism, which is that of charge transfer between the impurities. V-type centres, when present, are seen to be more stable in purer samples than in less pure samples, resulting in a shift of the TL peaks to higher temperatures. The TL mechanism in this case includes charge transfer between V-type centres and the impurities. The supralinear behaviour of TL peak 1 is associated with the R-emission lines of Cr3+.