CO ADSORPTION ON THE PD(110)C(2X4)-O SURFACE - FORMATION OF A P(2X4) STRUCTURE

The CO adsorption on the Pd(110)c(2x4)-O surface at 90 k has been inve stigated by using high resolution electron energy loss spectroscopy (E ELS), low-energy electron diffraction (LEED), and thermal desorption s pectroscopy (TDS). Three adsorbed states of CO have been found which a rt characterized by the C-O stretch energies of 235-237, 250-253 and 2 61-267 meV. It is proposed that CO molecules associated with these C-O stretch energies are adsorbed in the ''O-free'' long-bridge sites, th e ''O-coordinated'' long-bridge sites and the on-top sites of the c(2x 4)-O structure, respectively. The CO adsorption induces the formation of a p(2x4) structure, which is completed by the Formation of a Pd(110 )p(2x4)-(8CO+4O) structure at the saturation coverage (theta(CO)=1). T he structure model of the p(2x4)-(8CO+4O) surface is discussed.