THE COADSORPTION OF ETHENE AND CHLORINE ON AG(100)

We have characterised the low temperature adsorption of ethene on both clean and chlorine-precovered Ag(100) surfaces. On the clean surface at temperatures ca. 100 K ethene is found to be weakly pi-bonded at al l coverages with dynamic pressures of the gas being required to satura te the monolayer adsorption state. At high coverages, around the monol ayer point, repulsive adsorbate-adsorbate interactions induce a reorie ntation of the ethene which rotates the molecular plane towards the su rface normal. The interaction of ethene with a surface pretreated with Cl-2, is strongly dependent on the Cl coverage. At low values an enha ncement of the ethene-surface interaction via the formation of ordered ethene-chlorine structures is observed, although no substantial re-hy bridisation of the ethene is induced, while at high Cl coverage a prog ressive passivation of the surface is produced. The results presented are consistent with the formation of a simple chemisorbed layer of chl orine.