Flowing Afterglow Studies of Formation and Reactions of Cluster Ions of O2+, O2−, and O−

Abstract

The temperature‐controlled flowing afterglow system has been utilized at temperatures below 300°K to measure the rate constants for the association of H₂, N₂, O₂, CO₂, N₂O, and SO₂ to O₂⁺ with helium third body. Rate constants for the association of N₂, O₂, and CO₂ to O₂⁻ and for the association of N₂ and CO₂ to O⁻ have been measured at 200°K. Some of the ion clusters formed in this way reacted via binary neutral interchange reactions of the type A^±·B+C → A^±·C+B. Rate constants for these processes were obtained at and below 300°K. The observation of these reactions allows an ordering of ion cluster bond energies. The increasing order of binding energies to O₂⁺ is H₂, N₂, O₂, N₂O, SO₂, and H₂O. For the O₂⁻ ion clusters the increasing order is N₂, O₂, H₂O, CO₂, and NO. In some cases, equilibria are observed allowing a determination of binding energy differences. The three‐body association rate constants increase with increasing binding energy of the ion cluster, in accord with theoretical expectation.