Translational energy dependence of O+(4S)+N2→NO++N from thermal energies to 30 eV c.m

Guided ion beam mass spectrometry is used to examine the kinetic energy dependence of the reaction of ground state atomic oxygen ion with molecular nitrogen. An O+(4S) source which produces less than 0.06% excited states is described. Cross sections for the NO++N product channel decrease with increasing energy below 0.25 eV but increase with energy at higher energies. Analysis of the region above 0.25 eV finds an effective barrier of 0.33±0.08 eV which previous theoretical work suggests is on the N2O+(1 4A″) hypersurface. Below this barrier, ground state products can only be formed via a spin-forbidden surface transition. The magnitude and energy dependence of the probability for this transition are in reasonable agreement with a Landau–Zener formalism. These results are compared to previous ion beam, flowing afterglow (FA), and flow/drift tube (FD) studies. Apparent disagreement between the present data and previous FA and FD measurement is shown to be caused primarily by differences in the ion energy distributions.