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SLAC National Accelerator Laboratory

Illuminating the Multiconfigurational Ground State of Elemental and Intermetallic Compounds of Uranium and Plutonium
SSRL Science Summary - October 2012

Resonant x-ray emission spectra of actinide metals: Spectra show the emitted photon intensity as a function of the incident photon beam energy, EI, and the transfer energy, ET. Upper panel shows a sharp resonance dominated by a single uranium valence configuration. Bottom panel shows the broader resonance for the ground-state phase of elemental plutonium that is made up of differing amounts of three resonances = three valences.

The structural, electronic, and magnetic properties of U and Pu elements and intermetallics remain poorly understood despite decades of effort, and currently represent an important scientific frontier toward understanding matter. The last decade has seen great progress both due to the discovery of superconductivity in PuCoGa5 and advances in theory that finally can explain fundamental ground state properties in elemental plutonium, such as the phonon dispersion curve, the non-magnetic ground state, and the volume difference between different phases of the pure element.

A new feature of the recent calculations is the presence of multiple electronic configurations within their ground states, where the different properties of these materials are primarily governed by the different relative weights of these configurations. Using the new 7-crystal Johann-type spectrometer on Beam Line 6-2 at SSRL, Corwin Booth and a team of researchers from LBNL, LANL, LLNL and SSRL have collected resonant x-ray emission spectroscopy (RXES) data that show, for the first time, spectroscopic signatures of each of these configurations and their relative changes in various uranium and plutonium materials.

In combination with conventional XANES spectra on related compounds, these data indicate such states may be ubiquitous in uranium and plutonium intermetallics, providing a new framework toward understanding properties ranging from heavy fermion behavior, superconductivity, and intermediate valence to mechanical and fundamental bonding behavior in these materials.

Work was supported by the Office of Science, Office of Basic Energy Sciences (OBES), of the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. X-ray data were collected at SSRL, a national user facility operated by Stanford University on behalf of the DOE, OBES.


Primary Citation

C. H. Booth, Yu Jiang, D. L. Wang, J. N. Mitchell, P. H. Tobash, E. D. Bauer, M. A. Wall, P. G. Allen, D. Sokaras, D. Nordlund, T.-C. Weng, M. A. Torrez, and J. L. Sarrao, "Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics", PNAS 109, 10205 (2012) [DOI: 10.1073/pnas.1200725109]

Related Links


Corwin Booth, Lawrence Berkeley National Laboratory and Tsu-Chien Weng, SSRL

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