A selected ion flow tube study of the reactions of F +, Cl +, Br + and I + with several molecular gases at 300 K

Abstract

Using the selected ion flow tube technique, the rate coefficients and ion product distributions have been determined at 300 K for the reactions of the atomic halogen positive ions F +, Cl +, Br + and I + with some fifteen molecular gases, viz., (i) CO 2, CO, H 2, D 2 and N 2 (high ionisation energies), (ii) NO and O 2 (low ionisation energies), (iii) C 6H 6, C 2H 4, C 2H 2 and CH 4 (hydrocarbons with a spread of ionisation energies), (iv) NH 3, H 2S, OCS and H 2O (polar molecules with a spread of ionisation energies). Several distinct reaction processes are observed amongst the large number of reactions studied, including charge transfer, atom abstraction, hydride ion transfer and ion/molecule association. The particular reaction processes that occur are seen to be dependent on parameters such as the recombination energy of the reactant ion, the ionisation energy of the reactant molecule and the accessible electronic states in the product ion.