The Reaction of O(21D2) with Molecular Chlorine Studied by Atomic Absorption Spectroscopy in the Vacuum Ultra‐Violet

Abstract

AbstractA kinetic study of electronically excited oxygen atoms, O(21 D2), in the presence of molecular chlorine is presented. The optically metastable atoms were generated by repetitive pulsed irradiation of ozone in the Hartley‐band continuum and monitored photoelectrically in absorption by time‐resolved attenuation of atomic resonance radiation in the vacuum ultra‐violet at δ = 115.2 nm (O(3D1D20) ← O(21D2)) using signal averaging techniques. The absolute second order rate constant for total quenching by Cl2 is found to be kCl2 = 2.2 ± 0.2 · 10−10 cm3 molecule−1 sec−2 (300 K). Using the value for kO3 derived from previous measurements employing this method, we find that kCl1/kO3 = 0.81 ± 0.05, in substantial agreement with the ratio derived recently by Freudenstein and Biedenkapp who used an indirect procedure involving a complex kinetic analysis. The absolute datum for kCT2, coupled with Freudenstein and Biedenkapp's observation, provides the basis for discussing the various pathways for reaction of O(21D2) + Cl2 using symmetry arguments for both the weak spin orbit coupling approximation and (J, Q) coupling, in order to discuss individual spin orbit states.