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Comparative Photoemission Study of Actinide (Am, Pu, Np and U) Metals, Nitrides, and Hydrides

Published online by Cambridge University Press:  26 February 2011

Thomas Gouder
Affiliation:
thomas.gouder@ec.europa.eu, European Commission, JRC, Institute for Transuranium Elements, Fundamental Actinide Research, Postfach 2340, Karlsruhe, 76125, Germany
Alice Seibert
Affiliation:
alice.seibert@ec.europa.eu, European Commission, JRC, Institute for Transuranium Elements, Karlsruhe, 76125, Germany
Jean Rebizant
Affiliation:
jean.rebizant@ec.europa.eu, European Commission, JRC, Institute for Transuranium Elements, Karlsruhe, 76125, Germany
Frank Huber
Affiliation:
Frank.Huber@ec.europa.eu, European Commission, JRC, Institute for Transuranium Elements, Karlsruhe, 76125, Germany
Ladislav Havela
Affiliation:
lhavela@seznam.cz, Charles University, Faculty of Mathematics and Physics, Prague, 121 16, Czech Republic
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Abstract

Core-level and valence-band spectra of Pu and the other early actinide compounds show remarkable systematics, which can be understood in the framework of final state screening. We compare the early actinide (U, Np, Pu and Am) metals, nitrides and hydrides and a few other specific compounds (PuSe, PuS, PuCx, PuSix) prepared as thin films by sputter deposition. In choosing these systems, we combine inherent 5f band narrowing, due to 5f orbital contraction throughout the actinide series, with variations of the chemical environment in the compounds. Goal of this work was to learn more on the electronic structure of the early actinide systems and to achieve the correct interpretation of their photoemission spectra. The highly correlated nature of the 5f states in systems, which are on the verge to localization, makes this a challenging task, because of the peculiar interplay between ground state DOS and final-state effects. Their influence can be estimated by doing systematic studies on systems with different (5f) bandwidths. We conclude on the basis of such systematic experiments that final-state effects due to strong e-e correlations in narrow 5f-band systems lead to multiplet like structures, analogous to those observed in the case of systems with localized electron states. Such observations in essentially band-like 5f-systems was first surprising, but the astonishing similarity of photoemission spectra of very different chemical systems (e.g. PuSe, Pu2C3 and δ-Pu) points to a common origin, relating them to atomic features rather than material dependent density of states (DOS) features.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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