Trap levels in PbWO4 crystals: correlation with luminescence decay kinetics

X-ray excited luminescence, photoluminescence decay and thermally stimulated luminescence (TSL) measurements have been performed on a selected set of PbWO4 single crystals. At room temperature the X-ray excited emission spectrum is characterized by two components peaking at about 2.5 and 3.1 eV. The photoluminescence decay indicates the presence of a slow recombination component extending up to a ms timescale and related mainly to the 2.5 eV emission. Different TSL peaks have been observed in the 100–300 K range: direct correlation has been found between integrated intensities of TSL peaks detected above 200 K, the intensity of the slow decay component and steady state emission intensity measured at 2.5 eV. These results suggest that thermal detrapping from TSL traps and free carrier diffusion followed by their radiative recombination at luminescent centers are responsible for the slow decay processes observed.