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Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Bianconi, A., Congiu Castellano, A., Santis, M. D., Rudolf, P., Lagarde, P., Flank, A. M., & Marcelli, A. (1987). L2,3 XANES of the High Tc Superconductor YBa2Cu3O~7 with Variable Oxygen Content. Solid State Communications, 63(11). https://doi.org/10.1016/0038-1098(87)90650-8 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. No evidence of Cu &3d9 final states has been found. This experiment gives direct evidence that additional oxygen x does not give Cu3+ ions with Cu 3d* configuration but gives 3d"L electronic conliguration (I.c. Cu*-Q pairs) and no gap is observed bctwccn the 3d9 (Cu+) and 3d'OL configuration (l.c. C&O-pairs). Thcrcforc in the metallic phase which exhibits superconductivitya continous set of itinerant sta~cs 3d')L and 3ti'"L is obscrvcd. In order to show that the 933 eV peak is quenched with decreasing the oxygen content x we have reduced a sample by heating it in vacuum for 2 h at 400 "C. The 933 eV peak is reduced by the heat treatment as showed in fig. 4 where the spectra of the same sample before and after the heating in vacuum are compared. The difference spectrum between the heated and not heated sample shows a clear maximum at 933 eV and this feature overlaps the high energy side of the white line. THE ELECTRONIC CONFIGURATIONThe spectra of YBa2CU306.5+x (x-0.4) and of the The difference spectrum in fig. 4 shows the lineshape of KCu(biuret)2 show a new feature at 933 eV and 933.7 eV the derivative of the white line which can be assigned to a respectively in comparison with bivalent Cu compounds. In very small energy shift of the white line induced by sample fig. 3 it is clear that in there is an reduction. This shift is in the expected direction but it is overlap between this broad feature at 933 eV and the white smaller than experimental resolution of 0.1 eV.line, while in the insulating KCu(biuret)2 compound they are In order to assign the final state configuration of the 933 completely separated by 3 eV. eV feature we have measured the spectrum of the Cu20