Orbital excitation in Sr2CuO2Cl2: Resonant inelastic x-ray scattering at the Cu K pre-edge

We report resonant inelastic x-ray scattering (RIXS) study of d-d orbital excitations in Sr2CuO2Cl2 utilizing the intermediate state associated with a quadrupole transition. Fourfold azimuthal angle dependence of the pre-edge peak near the Cu K absorption edge confirms that the in-plane pre-edge peak arises from the 1s -> 3d(x2-y2) electric quadrupole transition. When the incident photon energy is tuned to this transition, we observed a RIXS excitation at 2 eV energy loss. This excitation is associated with the d-d excitation of d(x2-y2) -> d(yz,zx) based on the angular dependence of the quadrupole transition-matrix element of the scattered photon.