High energy resolution X-ray spectroscopy studies of U intermetallics at the U M4,5 edges

This contribution will provide an overview of applications of high energy resolution X-ray spectroscopic techniques to the U intermetallic systems. We will show resonant inelastic X-ray scattering (RIXS) and high energy resolution X-ray fluorescence detection (HERFD) X-ray absorption spectroscopy data from the uranium intermetallics UPd3, USb, USn3, URu2Si2 and others at the U M4,5 edges3 and compare the data to those from the well-localized 5f2 semiconductor UO2. We have found a small energy shift between UO2 and UPd3, both known to have localized 5f2 configurations, which we ascribe to the effect of conduction electrons in UPd3. The spectra from UPd3 and URu2Si2 are similar, strongly suggesting a predominant 5f2 configuration for URu2Si2. The valence-band RIXS provides information on the 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 these low-energy transitions reasonably well.
We will demonstrate that two new synchrotron-based techniques – HERFD and RIXS at the actinide M4,5 edges – can now provide unprecedented detailed information on processes such as the electron-electron interactions, hybridization between molecular orbitals, the nature of their chemical bonding, and the occupation and the degree of the f-electron localization.