Reaction of O+ with CO

Abstract

The apparent charge exchangereaction between O+ and CO has been studied for ground state ions in the energy range, E c.m., from threshold to 0.65 eV. The cross section was found to rise sharply at threshold (∞ 0.4 eV ) reaching a plateau at ∞ 0.6 eV . At Ec.m. = 2–3 eV, a further increase in the cross section is observed, and this rise is attributed to a new process, namely, the formation of CO+ in the A 2 Π state. The reaction has also been studied using excited O+ and in this case a threshold is not observed; furthermore, the cross section depends on the source of excited O+. Reactions of 18O+ with CO were studied and in both ground state and excited statereactions,electron transfer process was found to predominate. Kinetic energy analysis of the products showed two distinct groups of secondary ions: one at low energy (attributed to electron transfer products) and the other at high energy (attributed to ion‐atom interchange). From the measured kinetic energies of the secondary ions, −Q (the amount of kinetic energy tranferred into internal modes) was calculated. These results show that at E c.m. ≥ 8.5 eV the products of both processes decompose. At E c.m. ∞ 15.5–17.7 eV the ion‐atom interchange process occurs with ionization ( i.e., O + + CO → O + + CO + +e) . −Q was found not to be affected by the excitation of O+. The abundances of excited O+ formed upon bombardment of CO2 and N2O by 50‐V electrons are estimated to be 0.05 and 0.25, respectively. The state of excited O+ is discussed and the possibility that it may be 2 P is considered. A model for the reaction is briefly discussed.