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Thermal Decomposition of Hsub3O(-) Produced in Reaction of OH(-) with Hsub2CO

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The ion-molecule reaction OH- Hsub2CO yields Hsub3O- CO has been studied at 300 K with isotopic labeling of reactants. The Hsub3O- product is only observed in small abundance because the ion dissociates into OH- Hsub2 upon multiple collisions in a helium buffer gas. Without isotopic labeling, the pseudo-first-order kinetics plots for the reactions of OH- with Hsub2CO and OD- Dsub2CO were found to be curved as a result of the regeneration of OH- or OD- reactant. A scavenger technique was used to remove the Hsub3O- or Dsub3O- produced prior to dissociation, to reveal the true first-order attenuation of OH- or OD- in reaction with Hsub2CO or Dsub2CO. The rate constant for the OH- Hsub2CO reaction is 7.6 x 10 to the minus 10th power cc s-1, and for OD-1 Dsub2CO, is 5.7 x 10 to the minus 10th power cc s-1. For the isotopically mixed cases OH- Dsub2CO and OD- Hsub2CO, the rate constants are equal to 1.3 x 10 to the minus 9th power cc s-1, about twice as large as those for the reactions involving only a single hydrogen isotope, indicating that isotopic exchange is an important process. The rate constants for the thermal dissociation of Hsub3O- and Dsub3O- in helium were found to the 1.6 x 10 to the minus 12th power and 1.1 x 10 to the minus 12th cc s-1, respectively, within a factor of 2. The results are discussed in terms of other thermal dissociation reactions of ions.

Subject Categories:

  • Countermeasures
  • Isotopes
  • Atomic and Molecular Physics and Spectroscopy

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