Effect of annealing on absorption and roentgenoluminescence of PbWO4 crystals

The effect of annealing in vacuum, argon, and air on the absorption and roe ntgenoluminescence spectra of PbWO4 crystals was studied. Annealing in an o xygen-deficient atmosphere was found to bleach initially yellow crystals, s uppressing the absorption in the region from 375 to 500 nm; to reduce the i ntensity of the roentgenoluminescence band; and to shift it to shorter wave lengths. These effects are most pronounced at annealing temperatures from 7 50 to 800 degrees C. Subsequent annealing in air restores the original prop erties of PbWO4. The formation and dissociation of color and green-emission centers were correlated with the oxygen exchange between the environment a nd crystal during annealing in different atmospheres.