X-ray absorption L-III and M-V edges of hexavalent lower actinides

X-ray absorption spectroscopy is used to probe the electronic and structura l features of the actinides. To better understand the effect of the effecti ve charge and polyhedron on the edge structure, we discuss the L-m and M-v edges in AnO(2)(NO3)(2)(TBP)(2) (where the actinide is shortly linked to th e 'yl' oxygens) and in the perovskite Ba(2)ZnAnO(6) (where the hexavalent a ctinide is in the cubic structure as An(6+)), An = U, Np, Pu. Using FEFF8 s imulations, both features and position of the L-m and M-v edges are explain ed within a crystal field splitting of the orbitals picture and a multiple scattering picture. (C) 2000 Academic des sciences / Editions scientifiques et medicales Elsevier SAS.