Proton transfer reactions from H3+ ions to N2, O2, and CO molecules |
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Authors: | J.K. Kim L.P. Theard W.T. Huntress |
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Affiliation: | Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA |
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Abstract: | The rate constants for proton transfer from H3+ ions to N2, O2, and CO have been measured as function of hydrogen buffer gas partial pressure. The rate constant for proton transfer from H3+ to N2 shows a very large pressure dependence, increasing from 1.0 × 10?9 cm3/s at low H2 partial pressures to 1.7 × 10?9 cm3/s at high H2 partial pressures. The rate constants for proton transfer from H3+ to O2 and CO are constant with partial pressure of H2; giving values of 6.4 × 10?10 cm3/s and 1.7 × 10?9 cm3/s, respectively. The roles of excess vibrational energy in H3+ ions and of equilibrium between forward and back reaction are discussed. Back reaction is observed only for the reaction of H3+ ions with O2, and an equilibrium constant of K = 2.0 ± 0.4 at 298 K has been determined. From these data the proton affinity of O2 is deduced to be 0.47 ± 0.11 kcal/mole higher than that of H2. |
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