Interactions of O2 (b 1Σg+) with O(3P) and O3

Rate coefficients at 300°K have been measured for the reactions of O2(b 1Σg+) with O(3P) and with O3. Quenching of O2(b 1Σg+) by O(3P) proceeds with a rate coefficient of (8.0±2.0) ×10−14 cm3 molecule−1 sec−1. This means that O(3P) is probably of only marginal importance in quenching O2(b 1Σg+) in the thermosphere, although this conclusion depends on assumptions about the activation energies of the relevant reactions. A value of (2.2±0.2) ×10−11 cm3 molecule−1 sec−1 was found for O2(b 1Σg+) quenching by O3, in excellent agreement with two previous determinations. The product of the O(3P) yield in this reaction and the O2(b lΣg+) yield from O(1D) quenching by O2 was found to be 0.48±0.04. This leads to the conclusion that approximately 2/3 of O2(b 1Σg+)−O3 reactions lead to O3 dissociation. The quenching of O2(b 1Σg+) by O3 in the stratosphere may be a significant additional source of oxygen atoms.