Drift tube investigations on the reactions of O 2 + with CH4 and of CO 2 + with NO in various buffer gases

The influence of internal excitation on the reactions of O₂⁺ + CH₄ and of CO₂⁺ + NO has been investigated using a slow flow drift tube. The rate coefficients for these reactions obtained as a function of relative kinetic energy in various buffer gases like He, Ne, Ar, and Kr showed higher values under conditions where the internal excitation of the reactant ions was enhanced. For both reactions the lowest reactivity at all kinetic energies was observed to occur in He, indicating that He is the least effective buffer for collisionally inducing internal excitation of molecular ions.