Reaction of the CF₃ Radical with Various Cations (Ar⁺, Xe⁺, O₂⁺, NO⁺, CO₂⁺, C₂F₅⁺)

Abstract

The kinetics of reactions of the trifluoromethyl radical (CF₃) with several simple cations (Ar⁺, Xe⁺, O₂⁺, NO⁺, CO₂⁺, C₂F₅⁺) are studied via the variable electron and neutral density attachment mass spectrometry (VENDAMS) technique. CF₃ is produced via dissociative electron attachment to CF₃I, resulting in radical concentrations that are smaller than produced using pyrolysis methods, but better quantified. Rate constants and product branching fractions are reported, with typical uncertainties of ∼ 30%. Three of the reactions, Ar⁺, O₂⁺, and C₂F₅⁺ proceed near the calculated collisional rate constant, while the other reactions are between 10% – 30% efficient. The inefficiency of the reactions of Xe⁺ and CO₂⁺ can be explained by the reactions strictly obeying spin-conservation. The reaction of Ar⁺ yields predominantly (90%) CF₂⁺ via dissociative charge transfer, with a minor channel to CF₃⁺. The reaction of C₂F₅⁺ yields predominantly CF₃⁺ with a second channel (∼ 25%) yielding C₂F₄⁺ and CF₄, the only example here of a bond-breaking and bond-making reaction. For the other four reactions, only charge transfer to yield CF₃⁺ is observed. Rate constants for these same ions with CF₃I are also reported and found to be rapid with a variety of products formed.