Nascent rovibrational distributions of CO(d 3Δi,e 3Σ−,a′ 3Σ+) produced in the dissociative recombination of CO2+ with electrons

Abstract

The d 3Δi–a 3Πr, e 3Σ−–a 3Πr, and a′ 3Σ+–a 3Πr transitions of CO resulting from the dissociative recombination of CO2+(X̃ 2Πg:0,0,0) with electrons have been observed from the He afterglow reaction of CO2. The formation rate constants of CO(d), CO(e), and CO(a′) were estimated to be 1.6×10−7, 3.3×10−9, and 2.4×10−7 cm3 s−1, respectively. The vibrational and rotational distributions of CO(d:v′=0–6,e:v′=2,3,a′=3–11) were determined. Most of available excess energies (91%∼98%) were deposited into the vibrational energy of CO(d,e,a′) and the relative translational energies of the products, indicating that CO(d,e,a′) were produced by direct curve crossings between the entrance e−/CO2+(X̃ 2Πg:0,0,0) potential and repulsive CO(d,e,a′)+O(3P) potentials with linear geometries. The vibrational distributions of CO(d) and CO(a′) slightly shifted to lower states than those in photodissociation at a similar excitation energy. A simple statistical model was unable to explain the observed vibrational distributions obtained by dissociative recombination.