Resonant x-ray spectroscopy of uranium intermetallics at the M4,5 edges of uranium

We present resonant x-ray emission spectroscopic data from the uranium intermetallics UPd3, USb, USn3, and URu2Si2 at the M-4,M-5 edges of uranium, and we compare the data to those from the well-localized 5f(2) semiconductor UO2. The technique is especially sensitive to any oxidation of the surface, and this was found on the USb sample, thus preventing a good comparison with a material known to be 5f(3). We have found a small energy shift between UO2 and UPd3, both known to have localized 5f(2) configurations, which we ascribe to the effect of conduction electrons in UPd3. The spectra from U Pd-3 and URu2Si2 are similar, strongly suggesting a predominant 5f(2) configuration for URu2Si2. The valence-band resonant inelastic x-ray scattering provides information on the UP3 transitions (at about 18 eV) between the U 5f and U 6p states, as well as transitions of between 3 and 7 eV from the valence band into the unoccupied 5f states. These transitions are primarily involving mixed ligand states (O 2p or Pd, Ru 4d) and U 5f states. Calculations are able to reproduce both of these low-energy transitions reasonably well.