The electronic spectra of alkali metal uranates and band assignments: an analysis of their diffuse reflectance spectra

The diffuse reflectance spectra of alkali metal (Li, Na, K, Rb and Cs) mono - and diuranates, as well as several additional lithium polyuranates(VI), h ave been measured at 25 and -196 degreesC, and up to 500 degreesC for the p otassium uranates. The spectra of the mono- and diuranates of caesium and s odium were similar as were the spectra of the uranates of rubidium and pota ssium, because of identical site symmetries. Spectra recorded at -196 degre esC exhibited enough features to enable their resolution into individual ov erlapping bands. Existing theoretical models of the uranate spectra have be en critically examined. The recorded spectra were analysed using the MO dia gram for the octahedral UO66- moiety. The spectra were interpreted in terms of the various expected uranate ion site symmetries and the results obtain ed for all the alkali metal mono- and diuranates are reported here.