Rare Gas Quenching of Metastable O2 at 295 K

Abstract

The rare gas quenching rate constants of the metastable species, O2 was measured using an induced fluorescence technique that utilizes an incoherent broadband light source and an integrating sphere to maximize excitation efficiency and fluorescence light collection. The measured rate constants at 295 K were the following (in units of 10-20 cm3 molecule-1 s-1): He, 430 ± 13; Ne, 26 ± 5; Ar, 9 ± 5; Kr, 32 ± 3; Xe, 67 ± 5. These values are of much lower magnitude than previous results indicate. However, except for that of helium, these rate constants should be regarded as upper limits, given that water vapor and hydrogen (both highly efficient quenchers) are ubiquitous contaminants of gas samples. The quenching rate constant with ground-state oxygen derived from these experiments, (4.25 ± 0.52) × 10-17 cm3 molecule s-1, is in excellent agreement with previous results.