Photostimulated luminescence of halogen molecular ions in alkali borate glasses

ISSN： 0017-1050

Source： Glass Technology - European Journal of Glass Science and Technology Part A, Vol.44, Iss.2, 2003-04, pp. : 90-93

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Abstract

Photoluminescence spectra from halogen molecular ions in borate glasses have been observed for the first time. When alkali halide is added to alkali borate glasses, X₃^-(X; halogen) molecular ions are formed. The molecules give rise to one or two absorption bands in the ultraviolet regions. In the case of Br₃^- in glasses, when the sample was excited with light, an emission band was observed at 1950 nm. In the Cl₃^-, emission showed two bands at 800 and 1970 nm. It was found that these spectra depend weakly on alkaline species. The disappearance temperatures of luminescence were 30 and 150 K for Br₃^- and Cl₃^-, respectively. Nevertheless, the emission of I₃^- could not detected even at 4 K. (On the other hand, in some alkali halide crystals containing excess halogen, luminescence of V centres resembling that of X₃^- in glasses also has been observed.) From the experimental results for alkali borate glasses by comparing with luminescence of V centres, it is proposed that X₃^- in glasses show both absorption and emission spectra caused by Σ_u^*↔Σ_g, Π_g transitions, and are located about 6 Å away from host atoms and are not adjacent to alkali ions added to borate glass.