The character of doped holes in La1.9Sr0.1CuO4: polarization-dependent x-ray fluorescence study at the OK edge

Orbital-resolved O K alpha x-ray fluorescence spectra ofin-CuO2-plane [O(1) ] and epical [O(2)] oxygen atoms were obtained for La1.9Sr0.1CuO4 by making an appropriate choice of the energy of incident photons and the crystal or ientation relative to the polarization vector of the incoming radiation. Th e site origin of 2p(x,y) and 2p(z) components in the Sr-doping-induced abso rption prepeak near the O Is edge, associated with states developed in the energy gap, was studied by O K alpha monitoring at the excitation energy of the prepeak. The spectral analysis, based on the O K alpha shape differenc e between inequivalent O sites, supports the assignment of the doping-induc ed 2p(x,y) holes to the O(1) atoms but suggests that the 2p(z) holes may ha ve both O(2) and O(1) character in contrast to assignments in prior studies .