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.

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