A laboratory study on the dissociative recombination of vibrationally excited O₂⁺ ions

The production of metastable O(¹ S ) atoms by the dissociative recombination of O 2 + ions has been studied in a laboratory plasma spectroscopy experiment. The specific dissociative recombination coefficient for O( 1 S ) formation has a value of 2.1 × 10 −8 cm 3 s −1 , corresponding to an O(¹ S ) quantum yield of 10% at an apparent temperature of 296°K, in agreement with the earlier but less comprehensive measurements of Zipf [1970]. By using a variety of gas mixtures in order to modify the vibrational population of the O 2 + ions and laser‐induced photofluorescence techniques it was found that the laboratory O 2 + plasmas are vibrationally excited and that O 2 + ions in the υ′=4–12 vibrational levels are the chief source of the observed O( 1 S ) atoms. The specific O( 1 S ) dissociative recombination coefficient for O 2 + ( 2 π g ) ions in the lowest vibrational levels (υ′ ≤3) is much smaller (4.2 × 10 −9 cm 3 s −1 ). The implications of the quantum yield of 9.9% derived from Atmosphere Explorer data are discussed in the light of these findings. Preliminary electron‐heating experiments indicate that the specific O(¹ S ) recombination coefficient decreases with increasing electron temperature.