Bond-forming reactions of dications: Production of ArO+ and ArO2+ in the reaction of Ar2+ with O2

We present cross sections as a function of the collision energy for the bond-forming reactions of argon dications with oxygen molecules, producing ArO2++O and ArO++O+, respectively. Both the reactions are exothermic, and have cross sections much smaller than those of the competitive charge-transfer processes. The low-lying electronic states of ArO2+ have been calculated at the MR–AQCC/cc-pV5Z level. In contrast to previous results we found that the ground Σ-3 state has a local minimum. However, the estimated lifetime of this metastable state is too short to be detected in our setup. Thus the observed ArO2+ ions must be in the higher-lying Δ1 or Σ+1 states.