Oxygen negative ion reactions with carbon dioxide and carbon monoxide. Part 2

Abstract

The rate constant of the clustering reaction O^–₂+ 2CO₂→ CO^–₄+ CO₂ has been measured for near-thermal ions in a drift tube and mass filter and found to be 1.2 ± 0.2 × 10^–28 ml² molecule^–2 s^–1 at 298 K and pressures in the region of 1 Torr. The similar reaction with CO, O^–₂+ CO + CO₂→ CO^–₃+ CO₂, has been shown to have a rate constant more than 100 times smaller. An upper limit of 10^–16 ml molecule^–1 s^–1 is found for the reaction CO^–₄+ CO → CO^–₃+ CO₂. It is concluded that the values of these rate constants, together with those measured earlier ¹ for O^– cluster reactions, do not allow sufficient reoxidation of CO to CO₂ by simple ground-state oxygen negative ions to explain the apparent radiation stability of CO₂. Some alternative mechanisms are considered.