X-RAY-ABSORPTION SPECTROSCOPY OF ORGANOURANIUM COMPOUNDS IN THE (-STATES(V) AND (+IV) OXIDATION)

X-ray Absorption Spectroscopy (XAS) has been used to study monocyclooc tatetraene compounds of oxidation states IV and V. An updated version of ab initio code FEFF, FEFF7.0 has been tested at the L-3 edge of ura nium in order to extract reliable phases and amplitudes. EXAFS best fi t structural parameters have shown the lengthening of the U-Ligand dis tances with the increasing electronic charge of the complex. XANES at the L-3 and M-5 edges shows the screening effect of the additional 5f electron when the oxidation state of U varies from V to IV.