Kinetics for the reactions of O ^- and O ₂ ^- with O ₂(a ¹ Δ ₈) measured in a selected ion flow tube at 300 K

The kinetics of the reactions of O ^- and O ₂ ^- with O ₂(a ¹Δ _g) have been studied at 300 K in a selected ion flow tube (SIFT). The O ₂(a ¹Δ _g) concentrations have been determined using emission at 1270 nm from the O ₂(a ¹Δ _g, v = 0 → X ³σ _g ^-, v = 0) transition measured with an InGaAs detector calibrated against absolute spectrally dispersed emission measurements. The rate constants measured for O ^- and O ₂ ^- are 1.1 × 10 ^-10 and 6.6 × 10 ^-10 cm ³ s ^-1, respectively, with uncertainties of ±35%. The O ₂ ^- reaction only produces electrons and can be described as Penning detachment, while the O ^- reaction has been found to produce both O ₂ ^- and e ^-. The O ₂ ^- branching fraction has a lower limit of ∼0.30. Comparison of the present results to previous measurements found in the literature provides a resolution to a previous discrepancy in the rate constant values.