The soft X-ray synchrotron radiation methodologies near-edge X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) have been developed and employed at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory (LBNL) to elucidate the electronic structure of radioactive materials. Results from these investigations have begun to provide improved fundamental knowledge that can be used as a scientific basis for the enhanced design of actinide materials, complexes, ligands, and the overall understanding of actinide materials. The experimental developments at the ALS have largely centered on studies of radioactive materials with the Molecular Environmental Science (MES) soft X-ray scanning transmission X-ray microscope (STXM) at Beamline 11.0.2 for spatially-resolved investigations. The spectromicroscopy capabilities of the STXM provide the means to determine the speciation and composition in a range of actinide materials, particularly those of technological and environmental interest with spatial resolution that can reach to the true nanoscale. A particular emphasis has been on the use of the light atom (B, C, N, O, F, Na, Mg, Al, Si) ligand K–edge XAS technique to determine the electronic structure characteristics in an array of unique and relevant radioactive materials. Furthermore, there are a host of additional electron energy level thresholds (such as the L–edges of the transition metals, the M–edges of the lanthanides that and cesium plus others) that can be probed by near-edge XAS in the soft X-ray region. Recently, STXM spectromicroscopy studies have been extended to fast ion beam (FIB) prepared radioactive and irradiated material specimens in collaboration with Idaho National Laboratory. Complementing STXM spectromicroscopy are results from soft x-ray XAS/XES investigations that have largely centered on the actinide dioxides. The XES/XAS studies have investigated the nature of the electronic structure by probing both low-lying actinide and oxygen edges.

Soft X-ray synchrotron radiation studies of actinide materials

2019 Spring National Meeting

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