POLARIZED OXYGEN K-ALPHA AND COPPER L-ALPHA X-RAY-EMISSION SPECTROSCOPY OF YBA2CU3O7

The high temperature superconductor YBa2Cu3O7 is characterized by a ve ry anisotropic structure. The electronic structure of this compound is studied using high resolution valence band spectroscopy within an ele ctron probe microanalyzer. From single crystals and melt-textured spec imens, orientation dependent Cu-L(alpha) spectra are obtained using a beryl crystal. The Cu-L(alpha) spectra with polarization parallel to the z-direction show a larger energetic breadth compared to those obta ined with polarization perpendicular to z. This is caused by occupied Cu 3d(3x2-r2) like states, as could be shown by other workers using cl uster calculations. With a chlinochlore crystal, the polarized O-K-alp ha spectra can be used to investigate the orientation of single crysta l areas. The spectra map the bandlike O2p states. In contrast to the C u-L(alpha) spectra, the partial O-K alpha spectra agree with band stru cture calculations in the local density approximation done by other wo rkers.