Laser double-resonance study of the collisional removal of O2 (A 3Σ+u, ν=6, 7, and 9) with O2, N2, CO2, Ar, and He

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Abstract
The collisional removal of O2 molecules prepared in selected vibrational levels of the A 3Σ+u state is studied using a two‐laser double‐resonance technique. The output of the first laser excites the O2 to A 3Σ+u, ν=6, 7, or 9, and the ultraviolet output of the second laser monitors these levels via resonance‐enhanced ionization through either the ν=5 level of the C 3Πg Rydberg state, or the valence state or states tentatively associated with the 5 3Πg state. The temporal evolution of the A 3Σ+u state vibrational level is observed by scanning the time delay between the two pulsed lasers. Collisional removal rate constants are obtained for A 3Σ+u, ν=7 and 9 colliding with O2, N2, CO2, Ar, and He; and for ν=6 colliding with O2 and N2. We find the collisional removal of the A 3Σ+u state to be fast (k≥10−11 cm3 s−1) for all colliders studied. The rate constants vary by about an order of magnitude from the fastest collisional deactivator, CO2 to the slowest studied, the rare gases Ar and He. The rate constants for the atmospherically important colliders O2 and N2 are similar in magnitude and suggest that N2 collisions will dominate the removal rate in the Earth’s atmosphere.