Defects creation under UV irradiation of PbWO4 crystals.

A systematic study of photo thermally stimulated defects creation processes is carried out by the thermally stimulated luminescence (TSL) method for a large number of undoped and doped PbWO4 crystals under irradiation at 80-180 K in the 3.4-4.3 eV energy range. The activation energy Ea for the regular exciton state disintegration is found to be about 0.1 eV. For defect-related states disintegration, Ea varies in the crystals studied from 0.03 to 0.36 eV. The origin of the defect-related states is discussed. The conclusion is made that not only a release of charge carriers but also charge transfer processes take place under UV irradiation of PbWO4 crystals.