Raman spectroscopic studies of aqueous uranyl nitrate and perchlorate systems

Raman spectra have been obtained for the hydrate melts UO 2 (NO 3 ) 2 ·6H 2 O and UO 2 (ClO 4 ) 2 ·7H 2 O and for aqueous solutions of these salts over a wide range of solution composition. There was no evidence of ion-pair formation with uranyl perchlorate but uranyl nitrate formed a weak complex UO 2 NO 3 + with β 1 = 0.15 ± 0.04 at ionic strength 6.25. Complex formation was strongly enhanced by increased ionic strength. Raman depolarization measurements indicated both monodentate and bidentate linkage of nitrate to uranyl. Remarkably large changes in the molar scattering efficiencies of the nitrate modes accompanied the complex formation and suggested that there was considerable electron redistribution in the UO 2 NO 3 + complex.