Rovibrational product distributions of O2+ from the reaction of O+(4S) with CO2

Abstract

The nascent rovibrational population of O2 + produced from the reaction of near‐thermal O+(4 S)+CO2 is measured by observing the translational energy spectrum of its dissociative charge transfer products following neutralization in Cs vapor at keV energies. It is found that of the 1.19 eV exothermicity in the formation reaction, the product O2 + is formed on the average with 0.48 eV of internal energy partitioned nearly equally between vibrational excitation (0.27±0.03 eV) and rotational excitation (0.22±0.03 eV). Populations measured for O2 +(v=0−5) are: 0.38, 0.30, 0.18, 0.09, 0.05, 0.01, respectively. The O2 + rotational temperature decreases with increasing vibrational excitation, from T rot=3100 K in v=0 to T rot=450 K in v=5. The present populations show some disagreement with recent flow tube measurements. Details of the technique and a determination of the O2 + rovibrational population following electron‐impact ionization of O2 are also presented. The O+(4 S)+CO2reaction and its products are important in the ionospheres of Mars and Venus and in CO2 releases in the Earth’s ionosphere.