Negative ion-molecule reactions with atomic hydrogen in the gas phase at 296 °K

Gas phase reaction rates have been measured for the reactions of Cl⁻, I⁻, OH⁻, ${\mathrm{O}}_2^{-}$ , SF₆, and some hydrates of Cl⁻, OH⁻, and ${\mathrm{O}}_2^{-}$ with atomic hydrogen in a flowing afterglow system at 296°K. In general, the reaction mechanism is associative detachment, X⁻+H→HX+e, and the rate constants are very large (∼ 10⁻⁹ cm³/sec). The reactivities of Cl⁻, OH⁻, and ${\mathrm{O}}_2^{-}$ are reduced by clustering with H₂O. The reaction of I⁻ with H is immeasurably slow, and ${\mathrm{SF}}_6^{-}$ reacts with H to form ${\mathrm{SF}}_5^{-}$ which does not react further.