Lawrence Berkeley National Laboratory

Coupling High Energy Resolution Fluorescence Detection (HERFD) with electric dipole selection rules, the uranium 5f 5/2 and 5f 7/2 Unoccupied Densities of States (UDOS) have been determined in UF 4 , UO 2 and UCd 11 . Striking changes were observed between UF 4 (5f 2 ) to UCd 11 (5f 3 ), consistent with the Intermediate Coupling Model. Results for UO 2 were confirmed by Bremstrahlung Isochromat Spectroscopy (BIS). This new approach can be a powerful tool for shedding light on the hidden mysteries of Actinides 5f-electrons properties.