Collision induced desorption and dissociation of O2 on Pt(111)

We have studied desorption and dissociation of O2 on Pt(111) induced by incident energetic Xe atoms. The collision induced (CI) desorption rate was measured directly with a quadrupole mass spectrometer whereas the CI dissociation was investigated indirectly in post-Xe exposure TPD. We report the kinetics together with the energy, coverage, Xe incidence angle, and surface temperature dependences of the two processes. The cross sections for the two CI processes are determined via kinetic modeling, based on observed first-order CI desorption kinetics. There is a threshold in Xe kinetic energy at about 1.1 eV, common for both CI desorption and dissociation at normal Xe incidence. The Xe energy dependence of the cross sections for the two processes are well described by σdes=2.46⋅(EXe−1.1) (Å2) and σdiss=0.75⋅(EXe−1.1) (Å2), respectively, above the threshold at normal Xe incidence. A scenario where the O2–Pt bond is mechanically excited by an incident Xe atom, and where energy is transferred to the intramolecular bond via electronic coupling is presented. Implications of the results for the O2/Pt(111) PES are also considered.