科研之友
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摘要
Information on the position of A, B, and C bands of Pb2+ in 10 different fluoride compounds was collected. Environmental factors h(e) of the fluorides were calculated based on the dielectric theory of chemical bond for complex crystals. The relationships between the A, B, and C band energies of Pb2+ and h(e) were investigated. Three linear formulas were proposed. They allowed us to predict and assign the A, B, and C band energies of Pb2+-doped compounds and were also useful for identifying different Pb2+-occupied lattice sites. The model predicted that the positions of B and C bands for LiCaAlF6:Pb2+ are 162.9 and 150.9 nm, respectively. In BaY2F8:Pb2+, the excitation spectrum of Pb2+ from two different cation sites was identified: the higher energy bands of A, B, and C from the site of Y3+ and the lower ones from the site of Ba2+. For KMgF3:Pb2+, the absorption band at 187 nm from the site of K+, not Mg2+, was confirmed; moreover, the band at 218 nm was assigned to the A band of Pb2+ in the Mg2+ site. In addition, the origin of the B and C bands for BaY2F8:Pb2+ and LiBaF3:Pb2+ is discussed and reassigned.
