Model atomic oxygen reactions: Detailed experimental and theoretical studies of the reactions of ground-state O(3P) with H2, CH4, CH3CH3, and CH3CH 2CH3 at hyperthermal collision energies

Timothy K. Minton, Donna J. Garton, Diego Troya, Biswajit Maiti, Ronald Pascual, George C. Schatz

Research output: Contribution to journalConference article

1 Citation (Scopus)

Abstract

The reactions of O(3P) with H2, CH4, CH3CH3, and CH3CH2CH3 at center-of-mass collision energies in the range 1.5-3.9 eV have been investigated with (1) crossed-beams experiments employing a laser-detonation source of O atoms and (2) various theoretical methods. We present here the first measurements of the relative excitation function for the O(3P) + H2 reaction, and the experimental results are in excellent agreement with accurate quantum wave packet calculations. The experiment-theory agreement confirms that the laser-detonation source produces oxygen atoms in the ground O(3P) state. For reactions of O(3P) with alkanes, the experiments provide evidence for previously unobserved reaction pathways which principally lead to O-atom addition and subsequent H-atom elimination or C-C bond breakage: O(3P) + RH - RO + H or R'O + R″. In addition, the expected H-atom abstraction reaction to form OH has been observed. The H-atom abstraction reactions have modest barriers in the range ∼0.1 - 0.3 eV, whereas the addition pathways have barriers greater than ∼1.8 eV. Nevertheless, theory predicts that abstraction and addition reactions occur with similar probabilities at the collision energies of these studies. We have thus far completed one in-depth study of such an addition reaction: O(3P) + CH4 - OCH3 + H. Although high barriers prevent the addition reactions from occurring in most thermal environments, such reactions might be important in low-Earth orbit, where spacecraft surfaces and exhaust gases suffer high-energy collisions with ambient atomic oxygen.

Original languageEnglish
Pages (from-to)129-136
Number of pages8
JournalEuropean Space Agency, (Special Publication) ESA SP
Issue number540
Publication statusPublished - Oct 1 2003
EventProceedings of the 9th International Symposium on Materials in a Space Environment - Noordwijk, Netherlands
Duration: Jun 16 2003Jun 20 2003

ASJC Scopus subject areas

  • Aerospace Engineering
  • Space and Planetary Science

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