Inelastic and Reactive Scattering Dynamics of Hyperthermal O and O2 on Hot Vitreous Carbon Surfaces

Abstract

We have undertaken a series of experiments to learn the mechanisms of carbon oxidation over a wide range of temperatures that extend to the conditions encountered during atmospheric re-entry, with a particular interest in understanding how these mechanisms change with temperature. We report here the hyperthermal scattering dynamics of ground-state atomic oxygen, O(3P), and molecular oxygen, O2(3Σg–), on vitreous carbon surfaces at temperatures from 600 to 2100 K. A molecular beam containing neutral O and O2 in a mole ratio of 0.93:0.07 was prepared with a nominal velocity of 7760 m s–1, corresponding to a translational energy of 481 kJ mol–1 for atomic oxygen. This beam was directed at a vitreous carbon surface, and angular and translational energy distributions were obtained for inelastically and reactively scattered products with the use of a rotatable mass spectrometer detector. Unreacted oxygen atoms exited the surface through both impulsive scattering and thermal desorption. The preferred scattering ...