Reactions of N₂⁺ and N₄⁺ with O₂ from thermal to 20 eV center of mass

Reactions of N₂⁺ and N₄⁺ ions with O₂ are studied under single-collision conditions in a guided-ion beam mass spectrometer. Reactant ions are formed in a flow tube source to ensure thermalization. N₄⁺ is found to undergo charge transfer to O₂ more efficiently than does N₂⁺. The cross section for the latter reaction has a complex shape which is interpreted in terms of vertical transitions to form ground and excited state O₂⁺. For reaction of N₄⁺, the necessity of ligand exchange as an initial step is discussed. Cross sections for several other products, N₂O⁺, O⁺, NO ⁺, and N⁺, are measured for the first time in both systems and found to be formed only in endothermic reactions. Evidence is presented that the first three of these products arise from an N₂O⁺ intermediate for both systems. The present results are compared to and contrasted with previous measurements.