Optical Absorption on Cubic β-PbF₂ Crystals

The transmission spectra of cubic β-PbF₂ crystals grown by non-vacuum Bridgman method were measured with a spectrophotometer. It was found that there are several optical absorption bands peaking at 300 nm, 390-400 nm, as well as 460 nm. According to composition analysis, doping and annealing experiments, It is suggested that the absorption at 300 nm originate from the electron transition of Ce ions from 4f → 5d. The absorption at 390-400 nm may result from the color centers related to oxygen impurities. In addition, the sample recrystallized from the colored β-PbF₂ crystal exhibits a new absorption band at 460 nm, which might be caused by trace lead vacancies.