Al K_{α} excited photoelectron spectra (X-ray photoelectron spectroscopy) of the O 1s, Cu 2p, Ca 2p, Sr 3d core levels were measured for "infinite chain" Ca_{2}CuO_{3} and Ca_{0.5}Sr_{0.5}CuO_{2} compounds. The analysis indicates that for Ca_{2}CuO_{3} the surface electronic structure is strongly influenced by a humid atmosphere. The surface layer is formed predominantly by copper hydroxide. The minor features of Cu 2p and O 1s are characteristic of the bulk bonding states. The valences of the Cu, Ca, and Sr atoms are close to 2+. The core electron binding energies (≈ 934 eV peak) are due to the 2p_{3/2}3d^{10}L^{1} configuration of Cu(II) ions in the square planar coordination for both samples.
The electronic properties of Sr_{1-x}A_{x}CuO_{2+δ} (A = La, K, Ca) were examined. The crystal structure of the synthesized compounds was identified as orthorhombic with some admixture of tetragonal phase. For Sr_{1-x}La_{x}CuO_{2+δ} the insulator-metal like transition was observed with increasing La content. The d_{x²-y²} ground state of Cu ions was deduced from electron spin resonance measurements. The electronic state of Cu ions and their surrounding local symmetry was also found to be La and oxygen content dependent.
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