LINEARLY POLARIZED CU L3-EDGE X-RAY-ABSORPTION NEAR-EDGE STRUCTURE OF BI2CASR2CU2O8

The linearly polarized Cu L3-edge x-ray-absorption near-edge structure (XANES) of Bi2Sr2CaCu2O8 + delta has been measured and the spectra are interpreted by the full multiple-scattering approach in real space. The polarized spectra over a range of 20 eV can be predicted in terms of the one-electron dipole (DELTA-l = +1) transition Cu 2p --> epsilon-d, probing the unoccupied d-like (l = 2) density of states projected on the Cu site with orbital angular momentum m(l) = 0, 1 in the E parallel-to z spectra, and the m(l) = 2, 1, and 0 in the E perpendicular-to c spectra. The oscillator strength for the dipole allowed transitions (DELTA-l = -1) Cu 2p --> epsilon-s is shown to be a factor of 100 weaker than the 2p --> 3d transitions. The Coulomb interaction in the final state between the Cu 2p core hole and the excited Cu 3d electron is found to be 5.5 eV forming a bound state below the continuum threshold, the well-known Cu L3 white line. On the contrary, the core hole induces a nearly rigid redshift about 1 eV of the high-energy conduction bands.