Actinides relaxivity studies

Nuclear Magnetic Relaxation Studies on Actinide Ions and Models of Actinide Complexes Jean F Desreux... 

NUCLEAR MAGNETIC RELAXATION STUDIES ON ACTINIDE IONS AND MODELS OF ACTINIDE COMPLEXES... 

The Self-Consistent (SfC) (G)RECP version [23, 19, 24, 27] allows one to minimize errors for energies of transitions with the change of the occupation numbers for the OuterMost Core (OMC) shells without extension of space of explicitly treated electrons. It allows one to take account of relaxation of those core shells, which are explicitly excluded from the GRECP calculations, thus going beyond the frozen core approximation. This method is most optimal for studying compounds of transition metals, lanthanides, and actinides. Features of constructing the self-consistent GRECP are ... 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

With the advent of the use of kinematic pre-separators, as described in Section 2.2.2 above, the requirements of the chemical separation have been relaxed. It is no longer necessary to have the highest separation factors from interfering Bi, Po, and actinide radioactivities, so simpler separations which are more specific to the transactinide element being studied can be used. These relaxed separation requirements will allow development of simpler chemical separation techniques, and may lead to a new interest in manually performed chemical separations. 

Another common use of MC methods in metal chemistry involves the calculation of electronic spectra. In many cases, relaxation (in an orbital and geometric sense for the excited state) of the virtual orbitals is important, and hence the use of techniques such as MC methods that variationally optimize the virtual orbitals is essential for accurate reproduction of the spectroscopy of an organometallic. These methods, like all MC techniques, are computationally very intensive, and this often limits their application to very small model complexes. However, advances in software and hardware are constantly stretching the performance envelope of MC techniques. Roos and co-workers have reported MC studies pertinent to the spectroscopy of blue copper proteins and plastocyanin, and actinide complexes. 

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