Dynamics of Chemical and Charge-Transfer Reactions of Molecular Dications:  III. Beam Scattering and Total Cross Section Data for Processes in the System CO₂²⁺ + D₂

Abstract

Chemical reactions and charge-transfer processes in the system CO22+ + D2 were investigated in crossed-beam scattering experiments. Theoretical calculations of stationary points on the dication potential energy surface (CO2D2)2+ were carried out to complement the experiments. The main ion products identified were CO2D+, COD, CO2+, CO+, and O+. The relative cross sections for reactions with D2 (H2) were in the ratio CO2+:COD+:CO2D+ = 100:10:1 and were almost independent of the collision energy over the range 0.5−4 eV (center-of-mass, C.M.). The chemical product CO2D+ was formed in a nondissociative chemical reaction leading to CO2D+ + D+ through two channels that released different amounts of translational energy via decomposition of intermediates (CO2D2)2+; the high translational energy release channel (peak value at 4 eV) is consistent with the energetics of formation of a D−C-bonded isomer DCO2+, which dissociates further to form DCO+ + O. The charge-transfer product CO2+ is formed prevailingly in the excited states A and B; a small amount is also formed by further dissociation of the product CO2D+ (formed in the low translational energy release channel, presumably in an excited state) to CO2+ + D. The product CO+ results from two different processes: from charge transfer leading to CO2+(C2Σg+) + D2+ and predissociation of the C state to CO+(X2Σ+) + O(3P) and from spontaneous dissociation of the projectile CO22+ (vibrationally excited to its predissociation barrier) to CO+ + O+.