Ion–molecule reactions of Cl2 with Cl− and F−

Abstract

Using the flowing afterglow technique, we have examined the process Cl₂+Cl⁻→Cl₃⁻ in helium buffer gas. The system was studied over a range of helium pressures and the dependence of the apparent two‐body rate upon the buffer gas concentration gives a three‐body rate constant for the process: k = 0.9×10⁻²⁹ cm⁶ molecule⁻² s⁻¹. In addition, we looked at the analogous process involving a fluoride ion. There is no evidence for formation of the trihalide Cl₂F⁻ under our experimental conditions. A charge exchange process between Cl₂ and F⁻ to produce Cl⁻ and neutral ClF does occur, however. This rate is independent of the pressure of the helium buffer gas: k = 8.8×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹.