Dissociation of O2 chemisorbed on Ag (110) and Pt(111) induced by energetic Xe atoms

An energetic beam of Xe atoms causes the dissociation of adsorbed O2 molecules on cold Ag(110) or Pt(111) surfaces. This is a parallel channel to the previously observed collision induced desorption. Using EELS, mass spectrometry and TDS, the energy dependence of the collision induced 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 Pt(111). The branching ratios between desorption and dissociation, which are about 3 and 3.3 for Ag(110) and Pt(111), respectively, exhibit no or weak energy dependence.