O-1s x-ray near-edge absorption spectroscopy studies of La_1.5-xCa_xBa_1.5Cu₃O_y and La_1.5Ca_xBa_1.5-xCu₃O_y

The O-1s x-ray near-edge-absorption spectra of La_1.5-xCa_xBa_1.5Cu₃O_y have been measured by using synchrotron radiation. Their spectral features of the pre-edge spectra indicate that there is an electronic structure change similar to the effect of Pr in Y_1-xPr_xBa₂Cu₃O_7-δ; the holes on the CuO₂ planes increase with the doping concentration of Ca ions; not all the excess oxygen (for y≧7.0) in the basal plane supply holes; and there is a sign of increasing, rather than decreasing, the holes around the apical oxygen O(4) with the increase of the replacement of Ba by La on the Ba sites, an indication of a redistribution of holes.