Prediction of ultraviolet absorption spectra of p-block ions in oxide media. Possible application to redox equilibria in glasses and molten salts

Abstract

The heavier p block metal ions in their two oxidation states (upper state corresponding to the group number and the lower state two units less with the outer s² electronic configuration) give rise to intense absorption in the ultraviolet region. Absorption by the upper state arises through an electron transfer mechanism while that by the lower state is due to an inter-shell (s²→sp) transition. For the metal ions dissolved in oxide glasses, the positions of the absorption bands are shown to depend on the basicity, and quantitative relationships are derived between frequency maxima and the optical basicity of oxidic groups attached to the p block ions. These relationships allow spectral predictions to be made for p block ions which so far have not been studied in glass. Furthermore, when p block ions exist in both oxidation states it should be possible to analyse the ultraviolet absorption envelope for determining spectrophotometrically the oxidation state ratio upper state/lower state, e.g., in glasses or molten oxide media at elevated temperatures.