Radiolysis of LaF3 crystals with rare-earth impurities

Resumo

The absorption spectra of LaF₃ crystals, both pure and doped with rare-earth fluorides (YF₃, CeF₃, NdF₃, PrF₃, SmF₃, EuF₃, GdF₃, TbF₃, DyF₃, HoF₃, ErF₃, TmF₃, YbF₃, and LuF₃) have been investigated. All these impurities can be separated into two groups with respect to the shape of the absorption spectra of irradiated crystals. The spectra of the crystals doped with Nd, Sm, Tm, and Yb exhibit, along with 200-nm hole band F₃^-, weak bands due to RE²⁺-anion vacancy centers. The spectra of LaF₃ crystals with Y, Ce, Pr, Gd, Tb, Dy, Ho, Er, and Lu impurities exhibit, along with the hole-center bands (F₃^- at 200 nm and V_kA at 320 nm), bands of comparable intensity, which can be attributed to RE³⁺–F centers. This conclusion is confirmed by preliminary quantum-chemical calculations and the estimation of the levels location in the energy-band diagram.