ELECTRON-TRANSFER ON OXYGEN-COVERED AG(110) AND AL(111) SURFACES - WORK FUNCTION VERSUS LOCAL ELECTRONIC EFFECTS

The results of a study of changes in electron capture and loss rates i n the interaction of fluorine atoms and anions with oxygen-covered AI( III) and Ag(110) surfaces are reported for a wide range of coverages. A strong decrease in F- formation is observed. The magnitude of this d ecrease shows that the capture rates are much smaller than those expec ted on the basis of work-function changes. The observed decrease is as signed to changes in local electronic structure in the vicinity of the adsorbate site and modifications in positions and widths oi; the anio n levels. It was found that for incident F- and F-o the final F- fract ions are different, indicating that the memory of the initial charge s tate is not lost as in the clean metal case. This difference indicates that the electron-loss rate is smaller in the presence of oxygen. An incident-energy dependence of the loss process is observed, (C) 1998 P ublished by Elsevier Science B.V. All. rights reserved.