LOCALIZATION AND HYBRIDIZATION OF 5F STATES IN THE METALLIC AND IONIC BOND AS INVESTIGATED BY PHOTOELECTRON SPECTROSCOPY
Localization versus itineracy and the degree of hybridization of 5f states with orbitals of the actinide atom (especially 6 d) as well as with those of the ligand in compounds are central questions for the understanding of bonding in actinide solids. Photoelectron spectroscopy provides answers to these questions. In narrow band solids, like the actinides, the interpretation of results requires the use of band calculations in the itinerant picture, as well as models of final state emission in the atomic picture. From the experimental viewpoint: 1. the analysis of the variation of photoionization cross sections (affecting the intensities of photoelectron spectroscopy), gives an insight into the orbital composition of the bands of the solid; 2. the combination of direct and inverse photoemission provides a powerful tool to assess the structure of occupied and of empty states, and, in the case of localized 5f states, permits the determination of a fundamental quantity, the Coulomb correlation energy, governing the physical properties of narrow bands. After a survey of the basic theory and some experimental aspects of the photoelectron spectroscopy which are relevant to actinide solids, two systems are illustrated: elemental actinide metals, in which the Mott transition between plutonium and americium is evidenced in a photographic way by photoemission, and strongly ionic oxides, in which the 5f localized behaviour is clearly seen, and indications of f-p or d-p covalent are investigated.
Bibliographic Reference: PUBLISHED IN STRUCTURE AND BONDING, NO. 59/60, PP. 197-262, EDITED BY SPRINGER-VERLAG, 1985
Record Number: 1989123053300 / Last updated on: 1987-01-01
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