Collisional relaxation of vibrationally excited O2+ ions
- 1 November 1983
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 79 (9), 4201-4213
- https://doi.org/10.1063/1.446346
Abstract
Vibrationally excited O2+ ions were produced and injected into a helium flow tube and found to survive more than 105 collisions with He atoms without significant relaxation. The first, second, and higher vibrational states of O2+ were detected by their enhanced reactions with Xe, SO2, and H2O. Using these reactions as probes for vibrational excitation, the relaxation of O2+ (v=1) and O2+ (v=2) ions was studied for collisions with Ne, Ar, Kr, H2, D2, N2, CO, CO2, H2O, CH4, SO2, SF6, and O2. The resulting quenching rate constants were found to vary from 1(−9) to 3 s−1. The quenching rate constant of O2+ (v=2) was approximately twice that of O2+ (v=1) in each case. The rate constants were found to correlate with the bond energy of the ion–molecule collision complex. For CO2, Kr, and O2, the energy dependence of the quenching rate constant was investigated in the range 0.04–0.3 eV. The results indicate that the relaxation process proceeds through a long‐lived complex where the vibrational excitation is transferred into the weak complex bond resulting in dissociation, analogous to vibrational predissociation in van der Waals complexes. In the special case of O2+ (v)–O2 collisions, the relaxation is clearly dominated by the resonant charge transfer process and the rate constants for v=1 and v=2 are found to be equal.Keywords
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