Spectral properties and thermoluminescence of PbWO_4 crystals annealed in different atmospheres

摘要

Photoluminescence (PL) and their excitation spectra, cathodoluminescence (CL) and thermoluminescence (TL) of PbWO_4 crystals annealed in oxygen, air and vacuum have been investigated. The results indicate that the green luminescence is not caused by (WO_3 + F) centers but is probably related to (WO_4 + O_i). Assignment of the excitation states is also discussed. Some structural defects related to the oxygen vacancy (V_0) are the main mechanism inducing the fluorescence excitation band peaking at 378 nm and forming shallow traps corresponding to a TL peak at 134 K. The deeper traps shown by thermoluminescence at ca. 250 K originate from local oxygen excess defects.