(590a) Cooperative Effects Of Chlorine And Cesium On Surface Structure And Oxidation Reactivity Of Ag(111)

The interactions of chlorine and cesium alone and in combination with Ag(111) and Ag(111)-p(4x4)-O are investigated with temperature-programmed reaction spectroscopy, X-ray photoelectron spectroscopy, low energy electron diffraction, and scanning tunneling microscopy. Chlorine reconstructs the Ag(111) surface to a p(17x17) structure at 300 K. Subsequent adsorption of less than 0.1 ML cesium on this chloride covered surface produces a complex p(24x9) structure. Morphological changes to the Ag(111)-p(4x4)-O surface accompany the adsorption of chlorine and cesium on the oxide layer. Exposure of Ag(111)-p(4x4)-O to chlorine at 300 K forms a p(6x6) structure over the entire surface. The presence of pits and islands during the structure reorganization is indicative of the rearrangement of the Ag atoms in the adsorbate layer. Annealing the surface to 500 K, at which no desorption of chlorine and oxygen occurs, the surface further reconstructs to a new p(8x2) structure on the bunched steps. The structural transitions induced by chlorine and cesium may strongly affect the oxidation reactivity of the Ag(111) surface. The oxidation of CO and other hydrocarbons on different surface structures coexisting with chlorine, cesium, and oxygen will be discussed.