PNNL

Abstract

Plutonium occupies a pivotal position between lighter actinides, whose valence electrons display primarily itinerant characteristics, and heavier actinides, whose valence electrons behave as being more localized. The magnetic fields produced by Pu4+ centers in polycrystalline PuF4 have been measured by 19F NMR spectroscopy and analyzed to determine the description that applies to Pu. A model that assumes the Pu valence electrons are in localized non-interacting orbitals which produce dipolar fields cannot account for the width, shift, and anisotropy of the observed resonance. Alternative explanations involving covalent Pu--F bonding, superexchange interactions, and electronic configurations with enhanced magnetic moments are discussed. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, Heavy Element Chemistry program, and was performed in part in the William R. Wiley Environmental Molecular Sciences Laboratory, a D.O.E. national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for D.O.E. by Battelle.