Elucidation of the Off-Center Displaced Mo in Octahedral Coordination in BaMoO.

The detailed crystal structure as well as the heat capacity at low temperature and standard entropy of BaMoO are reported for the first time. High-resolution X-ray and neutron diffraction were employed to reveal the structural features of this compound. BaMoO has a six-coordinated Mo and a strongly negative excess volume with respect to the binary oxides.

The mechanism of Fe induced bond stability of uranyl(v).

The stabilization of uranyl(v) (UO ) by Fe(ii) in natural systems remains an open question in uranium chemistry. Stabilization of UO by Fe(ii) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(ii) induced stability and the change of the bonding properties have not been elucidated up to date.

Paving the way for examination of coupled redox/solid-liquid interface reactions: 1 ppm Np adsorbed on clay studied by Np M-edge HR-XANES spectroscopy.

The recently emerged actinide (An) M-edge high-energy resolution X-ray absorption near-edge structure (HR-XANES) technique has proven to be very powerful for oxidation state studies of actinides. In this work, for the first time, Np M-edge HR-XANES was applied to study Np sorption on illite. By improving the experimental conditions, notably by operation of the spectrometer under He atmosphere, it was possible to measure Np M-edge HR-XANES spectra of a sample with ≈ 1 μg Np/g illite (1 ppm).

Opportunities and challenges of applying advanced X-ray spectroscopy to actinide and lanthanide N-donor ligand systems.

N-donor ligands such as n-Pr-BTP [2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine] preferentially bind trivalent actinides (An) over trivalent lanthanides (Ln) in liquid-liquid separation. However, the chemical and physical processes responsible for this selectivity are not yet well understood. Here, an explorative comparative X-ray spectroscopy and computational (L-edge) study for the An/Ln L-edge and the N K-edge of [An/Ln(n-Pr-BTP)](NO), [Ln(n-Pr-BTP)](CFSO) and [Ln(n-Pr-BTP)](ClO) complexes is presented.

A Combined Study of Tc Redox Speciation in Complex Aqueous Systems: Wet-Chemistry, Tc K-/L-Edge X-ray Absorption Fine Structure, and Ab Initio Calculations.

The combination of wet-chemistry experiments (measurements of pH, , and [Tc]) and advanced spectroscopic techniques (K- and L-edge X-ray absorption fine structure spectroscopy) confirms the formation of a very stable Tc(V)-gluconate complex under anoxic conditions. In the presence of gluconate and an excess of Sn(II) (at pe + pH ≈ 2), technetium forms a very stable Tc(IV)-gluconate complex significantly enhancing the solubility defined by TcO(s) in hyperalkaline gluconate-free systems. A new setup for "tender" X-ray spectroscopy (spectral range, ∼2-5 keV) in transmission or total fluorescence yield detection mode based on a He flow cell has been developed at the INE Beamline for radionuclide science (KIT light source).

Exploring the electronic structure and speciation of aqueous and colloidal Pu with high energy resolution XANES and computations.

Pu L3 HR-XANES and FEFF9 computations provide evidence for band-like 6d states in colloidal Pu contrasting to narrow 6d states in molecular Pu(iv). Pu L3 HR-XANES is valuable for bond length estimation in plutonyl, whereas Pu M5 HR-XANES is an advanced tool for analysing Pu redox states and 5f unoccupied density of states.

Pu Coexists in Three Oxidation States in a Borosilicate Glass: Implications for Pu Solubility.

Pu(III), Pu(IV), and a higher oxidation state of Pu, likely Pu(VI), are for the first time characterized simultaneously present in a borosilicate glass using Pu M edge high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We illustrate that the method can be very efficiently used to determine Pu oxidation states, which control the solubility limit of Pu in a glass matrix. HR-XANES results show that the addition of excess SiN is not sufficient for complete reduction of Pu to Pu(III), which has a relatively high solubility limit (9-22 wt % Pu) due to its network-modifying behavior in glasses.

Adsorption of Selenium and Strontium on Goethite: EXAFS Study and Surface Complexation Modeling of the Ternary Systems.

Knowledge of the geochemical behavior of selenium and strontium is critical for the safe disposal of radioactive wastes. Goethite, as one of the most thermodynamically stable and commonly occurring natural iron oxy-hydroxides, promisingly retains these elements. This work comprehensively studies the adsorption of Se(IV) and Sr(II) on goethite.