INTERACTION OF SO2 WITH CLEAN AND CS-PRECOVERED AG(100)

The present paper gives a first report of our investigations of the adsorption and desorption kinetics of SO2 on clean and cesiated Ag(100) by means of TPD, DELTA-phi, molecular beam back scattering (MBBS) and isotope exchange experiments, assisted by AES and LEED. On clean Ag(100), SO2 is adsorbed only at temperatures T(ads) < 300 K. Although the TPD-spectra show similarities to our earlier measurements on clean Ag(110) and Ag(111), where SO2 was found to be adsorbed molecularly, distinct differences were obtained, especially concerning the SO2 sticking probability and the SO2 induced change of the work function. In addition, an exchange of isotopes was observed within the first monolayer. SO2 adsorption on Cs precovered Ag(100) leads to the formation of additional, Cs-influenced states at higher adsorption energies coexisting with clean silver SO2 states, indicating a short range CS-SO2 interaction. The Cs-influenced states are occupied first, leading to a strong re-increase of the work function.