The gas-phase reaction between BrO and CIO has been proposed as a potentially fast and synergistic mechanism of stratospheric ozone destruction. Further, it has been advanced1 as a contributing factor to Antarctic springtime ozone column losses of ∼40% from 1960 to 19852,3 Both dynamical4 and chemical theories1,5-8 have been advanced to explain the formation of the Antarctic 'ozone hole'. A major uncertainty in these theories has been the rate constant and product distribution of the BrO + ClO reaction as a function of temperature. Here we report the first direct measurements of these parameters. We show that this reaction could, indeed, account for a large fraction of the springtime ozone depletion over Antarctica and provide a source of chlorine dioxide of sufficient magnitude to explain the recent measurements of this species in the Antarctic stratosphere, provided that the stratosphere contains a sufficient quantity of bromine (∼20 p.p.t.v.). © 1987 Nature Publishing Group.

We have measured the rate constant for the reactions BrO + ClO → Br + OClO (6a), BrO + ClO → Br + Cl + O2 (6b), and BrO + ClO → BrCl + O2 (6c) over the temperature range 241-408 K and found k6 = (8.2 ± 1.0) × 10-12 cm3 molecule-1 s independent of temperature. Measurement of the individual product branching ratios yielded values for channels 6a, 6b, and 6c equal to 0.55 ± 0.10, 0.45 ± 0.10, and < 0.02, respectively. Measurements of ozone in the stratosphere over Antarctica have shown that the springtime ozone column has fallen 40% from 1960 to 1985. The reaction above could account for a large fraction of the springtime "ozone hole" reported recently, provided that at least 20 ppt of total inorganic bromine is present, and it may provide a source of chlorine dioxide of sufficient magnitude to explain the recent measurements of this species in the Antarctic stratosphere. © 1988 American Chemical Society.

Rates of the reactions S2 + O → SO + S (10), S2 + O2 → products (1), S2 + O3 → products (18), S2 + N2O → products (20), S2 + NO → products (21), S2 + NO2 → products (19) were investigated at 409 K and low pressure (0.89-3.0 Torr) in a discharge-flow system with mass spectrometric detection. Reaction 10 was found to be fast with k10 = (1.12 ± 0.20) × 10-11 cm3 molecule-1 s-1. Under the experimental conditions, S2 did not react with O2, O3, N2O, NO, or NO2. Upper limits for the rate constants of these reactions are k1 < 2.3 × 10-19, k18 < 4.0 × 10-15, k20 < 3.2 × 10-17, k21 < 8.5 × 10-17, and k19 < 1.1 × 10-15 cm3 molecule-1 s-1. Reaction 10 produced a large ion current at m/e 48 leading to the conclusion that S2 + O produces SO + S as primary products. © 1987 American Chemical Society.