Origin of the radiation-induced 420 nm color center absorption band in PbWO4 crystals

Polarized absorption spectra experiments were carried out to investigate the structural symmetries of color centers of PbWO4 crystals. It was found that the intensity of the electrical vector E⊥c of the radiation-induced 420 nm absorption band equals that of the E∥c, indicating the non-dichroic character of the band. Based on the analysis of the energy band structure and the crystal structure of PbWO4, the origin of the radiation-induced 420 nm absorption band was ascribed to the VF0 di-hole center.