Abstract We studied the reactive ion scattering (RIS) of Cs + from a Pt(1 1 1) surface adsorbed with CO and CO 2 leading to the emission of CsCO + and CsCO 2 + . 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 CO 2 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.