Building upon our recent work [1-9], a concerted effort to isolate and understand covalency and iconicity in uranium compounds has been pursued. Specifically, the isoelectronic formal charge systems, uranium dioxide and uranium tetrafluoride, have been investigated with a novel mixture of both soft and hard x-ray spectroscopies. The results to be discussed will include the following: (1) the use of soft x-ray O1s/F1s x-ray absorption spectroscopy (XAS) and U4d x-ray emission spectroscopy (XES) to follow the 2p/5f bonding via the unoccupied density of states; (2) the utilization of hard x-ray U L₃ extended x-ray absorption fine structure (EXAFS) to trivially distinguish the ordering in each: and (3) the use of hard x-ray L₃ resonant x-ray emission spectroscopy (RXES) to distinguish 5f occupation/covalency effects in UO₂ and UF₄

Acknowledgements

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, Lawrence Livermore National Security, LLC.

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