Determination of the Rate Constant of the Gas‐Phase Reaction between O(1D) and CO2

From the measurement of the amount of O3 produced by vacuum‐uv` flash photolysis of O2−Ar mixtures to which either CO2 or CO is added, a value of the ratio k5 / k3 = 55 ± 5 has been determined for the reactions O(1D) + CO2→CO3, O(1D) + CO→CO2. The results provide indirect evidence for the occurrence of Reaction (3) instead of Reaction (4), O(1D) + CO2→O(3P) + CO2.