Oxidation state determination of plutonium aquo ions using x-ray absorption spectroscopy

Four oxidation states (III, IV, V, and VI) of Pu may coexist under environmentally relevant conditions. An efficient method to determine the states actually present in various matrices would enhance the ability to model the fate and transport of plutonium in process streams and in the environment. This communication establishes that the L-3 X-ray absorption near-edge structure (XANES) spectra of Pu are primarily determined by the valence state and the presence or absence of the trans dioxo moiety, consistent with previous U and Np XANES studies. The edge energies were observed to shift progressively to higher energy with increasing valence, with an average 1.68 eV increase per formal oxidation state increase. Ih addition, the general spectral shape of the (III) and (IV) species is clearly different from the dioxo-containing (V) and (VI) species, with the first maximum much larger and sharper for the (III) and (IV) spectra than for the (V) and (VI) spectra. (C) 1998 Elsevier Science Ltd. All rights reserved.