SIFT studies of the reactions of rare gas atomic ions with Cl 2 and Br 2

Abstract

A selected ion flow tube (SIFT) study of the reactions of the rare gas positive ions He +, Ne +, Ar +, Kr + and Xe + with Cl 2 and Br 2 has been carried out at 300K from which the rate coefficients k and ion product distributions have been determined. For the very exothermic He + and Ne + ions reactions, dissociative charge transfer is the only observed process. For the less exothermic reaction of Ar + with Cl 2 both dissociative and non-dissociative charge transfer occurs. In the reaction of Ar + with Br 2 the main ion product is Br + but a small percentage of the stable rare gas—halogen dimer ion ArBr + was observed. Ions in two spin—orbit states of Kr + and Xe + (i.e. 2P 3/2, 2P 1 2 ) react at different rates with Cl 2 and Br 2, the 2P 1 2 excited state ions react more slowly than the 2P 3/2 ground state ions, consistent with previous results for the reactions of these ions with other molecules. The dominant process is charge transfer, which is dissociative in the case of Kr + + Br 2. Production of the stable ions KrCl +, KrBr +, XeCl + and XeBr + takes place exclusively in reactions of the ions in the 2P 1 2 states. secondary reactions of these rare gas—halogen ions with Cl 2 and Br 2 produce the triatomic ions Cl 3 + and Br 3 + which are unreactive with their parent ions. The rate coefficients of these secondary reactions have also been determined.