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Correlated measurements of emission spectra, photoluminescence and scintillation decays, thermoluminescence, and light yield were performed on a selected set of undoped and La-doped PbWO4 single crystals. The samples were grown from 5N purity raw powders and show the blue emission component only. Distinct influence of La doping was found in the decays, thermoluminescence and light yield characteristics. It is discussed in the light of the direct influence of La doping on suppressing the creation of point defect centers in the PbWO4 lattice, which are involved in the energy transfer and storage processes in this material.

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For the first time, photoluminescence of PbWO 4 :Bi crystals with different bismuth contents is studied by the time-resolved spectroscopy methods at 4.2-300 K. Photo-thermally stimulated processes of electron and hole centers creation under selective UV irradiation of the crystal in the 3-5 eV energy range and the 4.2-200 K temperature range are clarified, and the optically created electron and hole centers are identified by the thermally stimulated luminescence and electron spin resonance methods. The 2.2 eV emission of PbWO 4 :Bi crystals, excited in the Bi 3þ -related absorption band overlapped with the exciton absorption band, is shown to be of an excitonic origin and is suggested to arise from the excitons of two types localized around two different Bi 3þ -related centers.No emission, arising from the electron transitions between the energy levels of Bi 3þ ions, is observed. Photoexcitation of PbWO 4 :Bi crystals in the Bi 3þ -related absorption region results also in the creation of electron and hole centers. Three new paramagnetic centers are identified: (i) two holes trapped at two regular oxygen ions located close to a Bi 3þ ion and a lead vacancy V Pb (the {2O -À Bi 3þ À V Pb }-type hole centers); (ii) Bi 4þ centers; and (iii) the O À -type hole centers. The concentration of single (non-compensated) oxygen and lead vacancies as traps for electrons and holes, respectively, is found to be small. The processes resulting in the appearance of the Bi 3þ -related localized exciton emission and in the creation of Bi-related electron and hole centers are discussed.

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