title: Np(IV)/Np(V) valence determinations from Np L3 edge XANES/EXAFS.
abstract: X-ray absorption near edge structure (XANES) spectroscopy for in situ metal valence determination has become a powerful analytical tool in heterogeneous systems. This is in part because it is applicable without prior separation procedures. For some systems, however, determining the oxidation state from XANES spectra is not straightforward and caution must be used. We show that the analysis of L3,2 edge EXAFS (extended X-ray absorption fine structure) spectra is better suited to distinguish between Np(IV) and Np(V) than from their XANES spectra. Whereas evidence for the oxidation of Np(IV) in solution samples from their Np L3 XANES is unclear, their EXAFS data unequivocally reveals Np(V) formation in the solutions.
authors.affiliation: Forschungszentrum Karlsruhe GmbH, Institut für Nukleare Entsorgung, Postfach 3640, D-76021 Karlsruhe, Germany.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Denecke
authors.forename: Kathy
authors.initials: K
authors.lastname: Dardenne
authors.forename: Christian M
authors.initials: CM
authors.lastname: Marquardt