Raman scattering of actinide (VI) ions from carbonate media were obtained. Results indicate bidentate complexation of carbonate and linear geometry for the AnO2+2 ions. The trend of the frequency position of the v1 vibration in AnO2+2 ions is U > Np > Pu > Am in both acid and basic solutions, with higher frequencies occurring in acid media.
L. J. Basile, J. R. Ferraro, M. L. Mitchell, and J. C. Sullivan, "The Raman Scattering of Actinide (VI) Ions in Carbonate Media," Appl. Spectrosc. 32, 535-537 (1978)