Stereodynamics of the Charge Transfer Reactions between N ₂ ⁺ and O ₂

In this work, we investigate ion-molecule reactions N₂⁺ + O₂ → N₂ + O₂⁺/N₂ + O⁺ + O with the collision energies from 0.59 to 4.92 eV using the crossed-beam velocity map imaging technique, given the essential roles in atmospheric chemistry. For the charge exchange (CE) reactions at higher collision energies, the long-range collision leads to the forward-scattered O₂⁺ ions, while the O₂⁺ ions produced at the lowest collision energy of 0.59 eV show a diffuse distribution but basically along the collision axis. The latter is attributed to the formation of the long-lived intermediate complex [N₂O₂]⁺** in a short-range collision. Diffuse distributions of the O⁺ yield of dissociative charge exchange (DCE) are observed at 3.93 and 4.92 eV. By the data analyses using the Doppler kinematics model, we find that these O⁺ ions are produced not only from the predissociative O₂⁺** but also the intermediate N₂O⁺**, and these two intermediates can be formed, respectively, by the long-range and initimate collisions. The branching ratios of different DCE pathways are estimated, indicating the predominance of the N₂O⁺**-experienced pathways at relatively high collision energy.