Site specific and doping dependent electronic structure of YBa/sub 2/Cu/sub 3/O/sub x/ probed by ols and cu2p x-ray absorption spectroscopy

Summary form only given. The electronic structure of CuO/sub 2/ planes and CuO chains in single domain crystals of YBa/sub 2/Cu/sub 3/O/sub x/ has been investigated as function of oxygen concentration ( 6 /spl les/ x /spl les/ 7 ) using polarization dependent x-ray absorption spectroscopy on Ols and Cu2p levels. The polarization dependent observation of unoccupied states with O and with Cu orbital character parallel to the a, b, and c axes of the crystals allows the determination of hole states in Cu 3d/sub y/sup 2//-/sub z/sup 2// and O 2p/sub y,z/ orbitals in the CuO/sub 3/ chains. The number of holes is found to be correlated with the superconducting transition temperature and is no linear function of x.