A high-temperature guided-ion beam study of Na + X⁺ (X = O₂, NO, N₂) charge-transfer reactions

Abstract

The high-temperature guided-ion beam method is used to measure absolute, integral cross-sections for charge transfer reactions of sodium with O₂⁺, NO⁺ and N₂⁺ in the collision energy range between ca. 0.2 and 10 eV (CM). At 1 eV the cross-sections are, respectively, 168, 29 and 57 Ų, with errors estimated at ±40%. These experiments, involving molecular ions present in the ionosphere at altitudes of 80–110 km, were undertaken to improve the kinetic data available to the community involved in modelling mesospheric meteoric metal layers. The cross-sections are extrapolated to thermal energy, and thermally averaged rate constants are derived. The cross-sections are discussed with respect to the effects of vibrational excitation of the reactant ions, which are produced by electron impact ionization. These results permit an improved inclusion of metal-atom reactions in the models, which are now able to account for the kinetic energy range commensurate with the meteor ablation process.