Delayed Recombination Luminescence in Lead Tungstate (PWO) Scintillating Crystals

Photoluminescence decay in undoped, Mo- and (Mo,A)-doped PbWO4 crystals (A = Ce3+, Y3+, Nb5+) is measured for both blue and green emission components under the excimer laser excitation (308 nm) in the exciton absorption region. The fast first order and the delayed second order processes contribute to the decay in all cases. Thermal disintegration of the self-trapped exciton and (MoO4)2- emission centers can explain the observed behaviour. Codoping by aliovalent ions can efficiently modify the course of the delayed recombination decay components. Such codoping changes the concentration of shallow traps, which are responsible for retrapping free electrons and holes. Correlation with low temperature thermoluminescence characteristics is discussed.