Ion survival probabilities for 3 keV Ar + scattering from La, Yb, and chemisorbed H 2, O 2, and H 2O on La surfaces

Abstract

TOF spectra of scattered primary and surface recoiled neutrals and ions for 3 keV Ar + bombardment of clean La and Yb and H 2, O 2, and H 2O saturated La surfaces are presented. The spectra are analyzed in terms of single (SS) and multiple (MS) scattering of the primary ions and surface recoiling (SR) of adsorbate atoms. Measurement of spectra of neutrals + ions and neutrals alone allows determination of scattered ion fractions Y. The Y values for the SS event are high for clean La (37%) and lower for adsorbate covered La (32% for H 2, 13% for O 2, and 8% for H 2O); Yb exhibits a similar behavior, i.e. 16% for clean Yb and 5% for O 2 + H 2O covered Yb. Photon emission accompanying the scattering collision has been observed from clean La and Yb and adsorbate covered La. A preferential inelastic energy loss of 15 ± 3 eV for the SS event has been observed for scattered neutrals as opposed to ions for La and H 2 saturated La at 135°. These results are interpreted within the models for Auger and resonant electronic charge exchange transitions during approach or departure of an ion with a surface and the electron promotions occuring during close atomic encounters where the electron shells are interpenetrating.