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

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.