Rate constants for the reaction of O⁺ with NO as a function of temperature (300-1400 K)

We have measured the rate constants for the reaction of O⁺ ions with NO from room temperature to 1400 K. The reaction is slow (k = 8 × 10^-13 cm³ s^-1) at room temperature and the rate constant increases to 2.6× 10^-12 cm³ s^-1 at 1400 K. Comparison of the high-temperature data to drift tube data shows that rotational and translational energy are equally effective at controlling the rate constant, and that vibrational energy has at most a small effect on reactivity. Analysis of the data shows that the reaction proceeds by three different mechanisms. At the very low temperatures, we find a complex formation mechanism, and at the medium temperature range the behavior is interpreted to be a consequence of the correlation of O⁺(⁴S) and NO(²Π) with the excited states ³A₁, ³B₁ of NO⁺₂, which lie slightly above the reactants in energy. At the very high energy range, a third mechanism becomes important, probably the endothermic production of NO⁺(³Σ⁺).