Bond-forming reactions of molecular dications with rare gas atoms: Production of ArC2+ in the reaction CO2++Ar

Integral cross sections for the bond-forming reaction CO2++Ar→ArC2++O have been measured as a function of collision energy in a guided-ion beam mass spectrometer. The energy dependence is consistent with an endoergic reaction. Since the title reaction is in competition with several charge-transfer processes, the cross section at the maximum is only 0.023 Å2 at a collision energy of about 3 eV. Simple kinematics considerations suggest that the falloff of the cross section at higher energies might be due to the vibrational predissociation of ArC2+. State correlation diagrams are used for discussing the reaction mechanism.