We report the core-level x-ray photoelectron spectroscopy spectra of 30 intermetallic compounds of La and Ce. The results are discussed in the light of calculations using the Anderson impurity model of the 4f levels and including the degeneracy of the 4f levels. The comparison allows us to derive values for the coupling between the f levels and the conduction states 5 and the number of 4f electrons nf. We find 5 to be up to -150 meV in some Ce intermetallic compounds, and find nf to range from -0.8 -1.1. We cannot reconcile the core-level results with the traditional promotional model in which 6 was assumed to be 10 meV or less and the f-electron count could range from 1 down to zero in Ce intermetallic compounds. and superconducting properties, adherents of the promotional model thought that in A-rich Ce compounds the f level was completely above EF and was empty. As there would then be four conduction electrons per Ce atom these compounds were called quadrivalent.In the Ce compounds with the group-C elements the promotional model required no promotion of an f electron and the compounds were known as trivalent.Over the years several authors have questioned the applicability of the promotional model to Ce and its compounds (see, e. g., Refs. 17 -21) for, as shown in Ref. 15, many of the properties (e.g. , magnetic susceptibilities and anomalous lattice constants) attributed to f-electron promotion may be due to hybridization between the f levels and the conduction states. We will show that it is hard to understand core-level spectroscopic results on the basis of the promotional model. Combination of our theoretical framework with the experimental results leads us to deduce f-electron counts of -0.8 -1.1 and significant hybridization widths. We will list values for f-electron counts and widths for about 20 Ce com-27 7330

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Current R&D activities on materials for fusion power reactors are mainly focused on plasma facing, structural and tritium breeding materials for plasma facing (first wall, divertor) and breeding blanket components. Most of these activities are being performed in Europe, Japan, the People's Republic of China, Russia and the USA. They relate to the development of new high temperature, radiation resistant materials, the development of coatings that will act as erosion, corrosion, permeation and/or electrical/MHD barriers, characterization of candidate materials in terms of mechanical and physical properties, assessment of irradiation effects, compatibility experiments, development of reliable joints, and development and/or validation of design rules. Priorities defined worldwide in the field of materials for fusion power reactors are summarized, as well as the main achievements obtained during the last few years and the near-term perspectives in the different investigation areas.