Reactions of chlorine oxide radicals. Part 3.—Kinetics of the decay reaction of the ClO(X2Π) radical

Abstract

The kinetics of the decay reaction of the ClO(X²Π) radical have been investigated by time-resolved electronic absorption spectrophotometry in a discharge-flow system. Ar and Ar + SF₆ mixtures were used as carrier gases at 294 K; over the concentration range 45.31 × 10^–8[Ar]2.53 × 10^–8 g atom cm^–3 the decay reaction of ClO radicals was second order. Insignificant effects of third bodies (M = Ar, SF₆) were observed. Decay of ClO occurred predominantly under these conditions via reaction (2), [graphic omitted] with k₂= 10^{(11.89 ± 0.04)} exp [(–1150±50)/T] cm³ mol^–1 s^–1 in the temperature range 273 to 710 K. The low activation energy for reaction (2) and the large range of T^–1 of these measurements closely define the frequency factor for reaction (2).

The data were combined with earlier measurements of k_–2 by Johnston, Morris and Van den Bogaerde to give an accurate value for the dissociation energy of the ClOO radical, D^°₂₉₈(Cl—OO)=(29±3) kJ mol^–1.