Spectroscopic studies absorption, oxidation state analysis

A variety of methods have been used to characterize the solubility-limiting radionuclide solids and the nature of sorbed species at the solid/water interface in experimental studies. Electron microscopy and standard X-ray diffraction techniques can be used to identify some of the solids from precipitation experiments. X-ray absorption spectroscopy (XAS) can be used to obtain structural information on solids and is particularly useful for investigating noncrystalline and polymeric actinide compounds that cannot be characterized by X-ray diffraction analysis (Silva and Nitsche, 1995). X-ray absorption near edge spectroscopy (XANES) can provide information about the oxidation state and local structure of actinides in solution, solids, or at the solution/ solid interface. For example, Bertsch et al. (1994) used this technique to investigate uranium speciation in soils and sediments at uranium processing facilities. Many of the surface spectroscopic techniques have been reviewed recently by Bertsch and Hunter (2001) and Brown et al. (1999). Specihc recent applications of the spectroscopic techniques to radionuclides are described by Runde et al. (2002b). Rai and co-workers have carried out a number of experimental studies of the solubility and speciation of plutonium, neptunium, americium, and uranium that illustrate combinations of various solution and spectroscopic techniques (Rai et al, 1980, 1997, 1998 Felmy et al, 1989, 1990 Xia et al., 2001). 

Mononuclear complexes, [Ru(NH3)5(LH)]2+, where LH = Me2dicydl I, dicydl I and Cl2dicydH, have been prepared and characterized by electronic absorption spectroscopy and cyclic voltammetry.40 When deprotonated, the complexes oxidize to the Ru17 oxidation state and this allowed a spectroscopic analysis the RuIV-cyanamide chromophore. Only [Ru(NH3)5(Me2dicyd)]2+ could be isolated with sufficient purity to permit NMR studies, which suggested the metal ion was diamagnetic RuIv. 

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