A study of the gas phase reactions of various cations with two derivatives of SF6; SF5CF3 and SF5Cl

Abstract

A selected ion flow tube apparatus was used to investigate the positive ion chemistry of two derivatives of SF₆; SF₅CF₃ and SF₅Cl. This represents the first investigation of the positive ion chemistry of SF₅Cl, and much of the data on SF₅CF₃ is being presented here for the first time. Rate coefficients and ion product branching ratios have been determined at room temperature (300 K) for reactions with the following twenty-two cations; Ne⁺, F⁺, Ar⁺, N₂⁺, N⁺, CO⁺, CO₂⁺, O⁺, N₂O⁺, H₂O⁺, O₂⁺, SF₄⁺, CF₂⁺, SF⁺, SF₂⁺, NO₂⁺, SF₅⁺, NO⁺, CF⁺, CF₃⁺, SF₃⁺, and H₃O⁺ (listed in order of decreasing recombination energy). Comparisons are made in the text for the reactions of these ions with SF₆. SF₂⁺, NO₂⁺, NO⁺, SF₃⁺, and H₃O⁺ are found to be unreactive with both of the derivatives. The majority of the other reactions proceed with rate coefficients which are close to the capture value. The exceptions are the reactions of O₂⁺, SF⁺, SF₅⁺, and CF₃⁺ with SF₅CF₃, and SF₄⁺ and SF₅⁺ with SF₅Cl, all of which have rate coefficients significantly less than the capture mechanism value. Several distinct processes are observed among the large number of reactions studied, including dissociative charge transfer and various abstraction channels. Non-dissociative charge transfer is not observed, implying that any parent ions formed dissociate rapidly to the fragment ions and associated neutrals.