Rate constants for the quenching of metastable O2(1Σ) molecules

Singlet molecular oxygen, O₂(¹Σ), is one of the important intermediate species in the atmospheres of Earth, Mars, and Venus. To elucidate the chemistry of this excited molecular oxygen, a series of kinetic measurements have been undertaken using the flow-discharge/optical-emission technique. By monitoring the characteristic emission (762 nm for ¹Σ), the quenching rates for several important molecules have been obtained at room temperature. The following table summarizes measurements.

Quencher	Rate Constants (cm3/s)
CH2	(4.6 ± 0.5) × 10?13
H2	(7.0 ± 0.3) × 10?13
N2	(1.7 ± 0.1) × 10?15
Cl2	(4.5 ± 0.8) × 10?16
CO	(4.5 ± 0.5) × 10?15
O3	(2.2 ± 0.3) × 10?11
2,3 DBM-2	(6.0 ± 0.1) × 10?13

The error limits represent one standard deviation. The systematic error is estimated to be about 15%. For CO₂ and O₃ molecules, the quenching rate constants were also measured in the temperature range of 245–362 K. In both reactions, negligible temperature dependences (with the activation energy less than 0.6 kcal/mole) were observed.