Structural determination of the Pd{110}(2×1)p2mg-CO system by means of high-energy x-ray photoelectron diffraction

Abstract

The adsorption geometry of CO in the ͑2ϫ1͒p2mg phase on Pd͑110͒ has been determined by means of an application of high-energy x-ray photoelectron diffraction, which achieves adsorption site sensitivity in a forward scattering geometry. Information about the surface structure is extracted from the azimuthal angle dependence of the surface component of the Pd 3d 5/2 photoemission peak. Surface sensitivity is obtained by working at grazing emission angles. The experimental data are compared with single scattering cluster simulations, giving clear evidence that the CO molecules are located in short-bridge sites. The estimated Pd-C distance is 1.86Ϯ0.09 Å. A CO tilt angle of 24Ϯ3°from the surface normal was determined by means of the C 1s polar scan along the plane normal to the ͓001͔ direction. ͓S0163-1829͑96͒09327-1͔