A study of the reactions of the ground and metastable states of C +, N +, S + and N 2+ at 300 K

Abstract

The reactions of the ground and metastable states of C +, N +, S + and N 2 + with H 2, CO, NO, O 2, CO 2, H 2O, NH 3 and CH 4 at 300 K have been studied using a selected ion flow tube (SIFT) apparatus. Reaction rate coefficients have been determined for the ground and metastable states of N +, S + and N 2 +, and for the last two ions it has been possible in some reactions to distinguish two metastable states through their different reaction rate coefficients. The measured ground state rate coefficients generally agree with previous measurements and the metastable rate coefficients are usually higher, approaching gas kinetic values. In the case of S + and N 2 +, collisional quenching of the metastable to the ground state ions by the reactant gas has been observed and this process can account for up to half of the loss of the metastable ions. Product ion distributions for the mixture of ground and metastable states have been determined for the reactions of all four ions and from these it has been possible to unfold the product ion distributions for the metastable state using the values previously reported for the ground state ions. The similarities and differences in the reaction mechanisms of the ground and metastable state ions are briefly discussed.