Evidence for Eley-Rideal abstraction mechanism in reactive ion scattering of Cs+ from Pt(1 1 1) adsorbed with CO and CO2

We studied the reactive ion scattering (RIS) of Cs+ from a Pt(1 1 1) surface adsorbed with CO and CO2 leading to the emission of CsCO+ and CsCO2+. The RIS products were measured as functions of adsorbate coverage and ion incidence energy for the range of 10-60 eV. The yield and cross-section for the RIS processes were extracted from these measurements. The RIS cross-section is higher for weakly adsorbed CO2 than for more strongly bound CO. The RIS energy-dependence shows a maximum at 15-20 eV and a decrease at higher energy. These observations provide evidence for the theoretically proposed mechanism of RIS, in which a slow Cs+ picks up an adsorbate in an Eley-Rideal abstraction reaction.