DISSOCIATION OF O-2 CHEMISORBED ON AG(110) AND PT(111) INDUCED BY ENERGETIC XE ATOMS

An energetic beam of Xe atoms causes the dissociation of adsorbed O-2 molecules on cold Ag(110) or Pt(111) surfaces. This is a parallel chan nel to the previously observed collision induced desorption. Using EEL S, mass spectrometry and TDS, the energy dependence of the collision i nduced dissociation and desorption cross sections was measured over a range of Xe beam energies, On both surfaces these events seem to have a common threshold energy of about 0.9 eV for Ag(110) and 1.2 eV for P t(111). The branching ratios between desorption and dissociation, whic h are about 3 and 3.3 for Ag(110) and Pt(111), respectively, exhibit n o or weak energy dependence.