Actinides spectroscopic studies

Special techniques for experimentation with the actinide elements other than Th and U have been devised because of the potential health ha2ard to the experimenter and the small amounts available (15). In addition, iavestigations are frequently carried out with the substance present ia very low coaceatratioa as a radioactive tracer. Such procedures coatiaue to be used to some exteat with the heaviest actinide elements, where only a few score atoms may be available they were used ia the earHest work for all the transuranium elements. Tracer studies offer a method for obtaining knowledge of oxidation states, formation of complex ions, and the solubiHty of various compounds. These techniques are not appHcable to crystallography, metallurgy, and spectroscopic studies. 

The only crystalline phase which has been isolated has the formula Pu2(OH)2(SO )3(HaO). The appearance of this phase is quite remarkable because under similar conditions the other actinides which have been examined form phases of different composition (M(OH)2SOit, M=Th,U,Np). Thus, plutonium apparently lies at that point in the actinide series where the actinide contraction influences the chemistry such that elements in identical oxidation states will behave differently. The chemistry of plutonium in this system resembles that of zirconium and hafnium more than that of the lighter tetravalent actinides. Structural studies do reveal a common feature among the various hydroxysulfate compounds, however, i.e., the existence of double hydroxide bridges between metal atoms. This structural feature persists from zirconium through plutonium for compounds of stoichiometry M(OH)2SOit to M2 (OH) 2 (S0O 3 (H20) i,. Spectroscopic studies show similarities between Pu2 (OH) 2 (SOO 3 (H20) i, and the Pu(IV) polymer and suggest that common structural features may be present. 

Group IVB, actinide, and lanthanide, hydrothermal hydrolysis spectroscopic studies. 58-62... 

Storage, nuclear waste, x-ray photoemission spectroscopic study of actinides in silicate-based... 

ILs is in the range of 230-250 nm) which make them suitable to be used as solvents for spectroscopic measurements especially in the visible region. Because of their ionic origin, ILs allow the coordination of a complex compound in a liquid sfafe to be sfudied. An additional advanfage of ILs is that their solvating properties can be designed in such a way that differently coordinating solvents are obtained. A lot of examples can be presented on spectroscopic studies with lanthanides and actinides. 

This involves the use of tertiary amine extraction of the An ions from acidic 11 M LiCl solutions. Spectroscopic studies have indicated that, in the cases of Am and Nd at least, the octahedral trianionic hexachloro complexes are extracted from 11 M LiCl. Stability constant data for the chloride complexing of Am , and Cfin media of ionic strength 1,0 have been reported. Tertiary amines also extract Pu and a study of extraction from nitrate media by trilaurylamine (TLA) in xylene has been reported. " This showed that the mass transfer rate was controlled by the reactions between Pu from the bulk phase and interfacially adsorbed TLA-HNOs. The separation of individual transplutonium elements from the Tramex actinide product may be achieved using ion exchange or precipitation techniques." ... 

In summary, the calculations on this special impurity system, with only one open-shell electron and simple manifolds, in which the assigmnents of the 5/<-> 6d absorption/emission bands were specially clear, even though not complete, and where absorption/emission bands built on a single origin and recorded with an extremely hi resolution exist, allow to be initially optimistic in the evaluation of the applicability of present day ab initio methods of the Quantum Chemistry in structural and spectroscopic studies of actinide ion impurities in ionic crystals. The quality of the approximate Hamiltonians and of the approximate procedures for decoupling the treatment of electron correlation and spin-orbit seems to be acceptable. The performance in other impurities with several open-shell electrons and large manifolds will be presented in the next two sections. 

Spectroscopic studies of superdefonned fission isomers have been reviewed (Vandenbosch 1977 Metag et al. 1980 Bjornholm and Lynn 1980), while hyperdeformed nuclear shapes in the third minimum of the potential energy surface was discussed by M5ller et al. (1972) and recently by Cwiok et al. (1994). Krasznahorkay et al. (1998) succeeded to observe hyperdeformed rotational bands in actinide nucleL... 

To probe the bonding in the above types of compounds, Ciliberto, Condorelli, Fagan, Manriquez, Fragala, and Marks [45] carried out a comparative gas phase He I/He II photoelectron spectroscopic study of the series CP2MCI2 and Cp2M(CH3)2, M Zr,Th,U. It was found that the bonding in the early transition metal and actinide complexes is surprisingly similar. The major differences between zirconium and the actinides could be ascribed to the involvement of 5f orbitals in the latter. 

The mechanisms of actinide/lanthanide binding to transferrin may not be the same as that for iron( III). Spectroscopic studies by Duffield and Taylor(1987) have shown the fine details of Pu(IV) and Th(IV) binding to transferrin to be very similar to that of Fe(III). 

The existence of a proper y-ray transition is an outcome of nuclear structure. Therefore, a Mdssbauer transition is coupled to a certain isotope of the atom of interest. A low isotopic abundance of the resonant isotope may be a serious restriction. Next, if the excited state is rather short lived then F becomes wide and the resolution for hyperfine spectroscopy (see section 2.3) becomes too limited. The same effect can be caused by unfortunate values of nuclear moments of the two states involved in the Mdssbauer transition. Finally, difficulties to produce the source activity may hinder a wider application of measurements with that particular isotope. Difficulties in source preparation and poor resolution are, for example, present in and have prevented Mdssbauer spectroscopic studies of compounds of this most interesting actinide. 

Investigations may be carried out on the tracer level, where solutions are handled in ordinary-sized laboratory equipment, but where the substance studied is present in extremely low concentrations. Concentrations of the radioactive species of the order of 10 m or much less are not unusual in tracer work with radioactive nuclides. A much larger amount of a suitably chosen non-radioactive host or carrier is subjected to chemical manipulation, and the behavior of the radioactive species (as monitored by its radioactivity) is determined relative to the carrier. Thus the solubility of an actinide compound can be judged by whether the radioactive ion is carried by a precipitate formed by the non-radioactive carrier. Interpretation of such studies is made difficult by the formation of radiocolloids, and by adsorption on glass surfaces or precipitates. Tracer studies provide information on the oxidation states of ions and complex-ion formation, and are used in the development of liquid-liquid solvent extraction and chromatographic separation procedures. Tracer techniques are not applicable to solid-state and spectroscopic studies. Despite the difficulties inherent in tracer experiments, these methods continue to be used with the heaviest actinide and transactinide elements, where only a few to a few score atoms may be available [11]. 

B. Brendebach, N. Banik, C. M. Marquardt, J. Rothe, M. Denecke, and H. Geckeis, X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH... 

The techniques used in the work have generally been spectroscopic visible-uv for quantitative determinations of species concentrations and infrared-Raman for structural aspects of the polymer. Although the former has often been used in the study of plutonium systems, there has been considerably less usage made of the latter in the actinide hydrolysis mechanisms. 

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