Abstract
Superconductors with the composition La/sub 2-//sub x/(Ba,Sr)/sub x/CuO/sub 4-//sub y/ and x = 0.0 to 0.3 have been studied through measurements of x-ray-absorption near-edge-structure at the Cu K and La L edges. Contrary to recent band-structure calculations, we find that the Cu 3d electrons are localized with the copper ions having an integral 3d/sup 9/ configuration (2 + valence) independent of dopant concentration. Variation in the area of the ''white lines'' at the La L/sub 2,3/ edges with doping indicates that reduction of the valence charge results in an increase in unoccupied states (probably consisting of holes in the O 2p band) having d symmetry relative to the La site. These O 2p holes also appear to have d symmetry with respect to the Cu sites.
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