TRANSMISSION OF LOW-ENERGY (LESS-THAN-10 EV) O-GAS FILMS( IONS THROUGH SEVERAL MONOLAYER THICK RARE)

We present the first systematic study of the transmission of low energ y oxygen ions (< 10 eV) through ultrathin films of Ar, Kr, and Xe. For rare gas films adsorbed on an oxidized W(100) surface, we find that a small fraction of O+ can penetrate more than 5 ML thick films of Kr a nd Xe. The attenuation of O+ is strongest for Ar overlayers. We attrib ute the attenuation mainly to elastic scattering of the ions with the rare gas atoms. We suggest that structural characteristics of rare gas films adsorbed on this surface are the cause for low attenuation in t he first 1-2 monolayers.