THE ELECTRONIC-STRUCTURE OF THE SURFACE METHOXY SPECIES ON CU(111)

Using model calculations for a CU25OCH3 cluster the bonding interactio n between the methoxy species and a Cu{111} surface has been investiga ted. In agreement with recent photoelectron diffraction measurements, OCH3 is found to adsorb preferentially in the fcc three-fold hollow si te with its O-C axis perpendicular to the surface. The corresponding v ibrational spectrum - measured with high resolution electron energy lo ss spectroscopy - is compatible with this bonding geometry. Moreover, on the basis of the known structure, selection rules are used to defin itively assign the adsorbate-induced features in the photoemission spe ctrum. There is good agreement between the measured ionisation potenti als and those obtained from the model calculations via Koopmans' theor em. Taken together, the results confirm a bonding picture in which cha rge transfer of metal electrons fills the 2e orbitals of the adsorbed OCH3 Species, leading to a largely ionic bond.