Actinide Ions In Solution Research Articles

X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH values

Abstract We perform X-ray absorption spectroscopy (XAS) investigations to monitor the stabilization of redox sensitive trivalent and tetravalent actinide ions in solution at acidic conditions in a pH range from 0 to 3 after treatment with holding reductants, hydroxylamine hydrochloride (NH2OHHCl) and Rongalite (sodium hydroxymethanesulfinate, CH3NaO3S). X-ray absorption near edge structure (XANES) measurements clearly demonstrate the stability of the actinide species for several hours under the given experimental conditions. Hence, structural parameters can be accurately derived by extended X-ray absorption fine structure (EXAFS) investigations. The coordination structure of oxygen atoms belonging to water ligands surrounding the actinide ions does not change with increasing pH value (approximately 11 O atoms at 2.42 Å in the case of U(IV) at pH 1, 9 O atoms at 2.52 Å for Np(III) at pH 1.5, and 10 O atoms at 2.49 Å for Pu(III) up to pH 3), indicating that hydrolysis reactions are suppressed under the given chemical conditions.

Similarities between the Coordination of Actinide Ions in Solution and the Structures of their Related Crystalline Phases

AbstractHigh-energy x-ray scattering (HEXS) is used to probe correlations about selected actinide ions in solution. The experiments were designed to favor homoleptic water coordination in order to compare the preferred structural environment of UO22+, NpO2+, and Cm3+ with similar ligands. In addition to comparisons between the three actinide ions in solution, the results from the HEXS studies are also compared with known solid state structures. Marked similarities are found between near- and next-near neighbor coordination in solution and in the solid state.

Cation—Cation Interaction in Crystalline Actinide Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.

F-State luminescence of trivalent lanthanide and actinide ions in solution

Detailed studies of the luminescence of aquated Am 3+ are presented in the context of prior work on lanthanide and actinide ions. The luminescing state of aquated Am 3+ is confirmed to be 5D 1 based on observed emission and excitation spectra. The luminescence lifetime of Am 3+ in H 2O solution is (22±3) ns and (155±4) ns in D 2O solution at 295 K. Judd—Ofelt transition intensity theory qualitatively describes the observed Am 3+ relative integrated fluorescence intensities. Recent luminescence studies on complexed trivalent f-element ions in solution are reviewed as to the similarities and differences between the lanthanide ion 4f state and the actinide ion 5f state properties.

Laser photochemistry of metal ions with f electrons.

Laser photochemistry of lanthanid and actinideions in solution is briefly reviewed. A typical example is the photoreduction of Eu3+ in aqueous solution. A nanosecond laser photolysis techniquewas applied to this reaction. The reduction yield was found to be several percent. Detailed studies on these metal ions will provide new methods for nuclear reprocessing.

Neutron scattering from solutions: The hydration of lanthanide and actinide ions

The neutron scattering difference method is described and applied to investigations of the aqua rare earth ions, Nd 3+ and Dy 3+. Metal-water distances and hydration numbers have been unambiguously determined for the inner coordination spheres of these ions. The values of the hydration number n of 8.5 ± 0.2 for Nd 3+ and 7.4 ± 0.5 for Dy 3+, directly support the claim of Spedding et al. that n decreases by one unit across the lanthanide series. The possible application of this method to actinide ions in solution is also discussed.