Heterogeneous recombination of O + CO on solid CO 2 at 77 K

Heterogeneous recombination of O + CO → CO 2 over a solid CO 2 surface at 77 K was investigated. A modified discharge flow setup was used to generate low O atom concentrations by the reaction N + NO → N 2 + O( 3 P). The O atom concentrations were measured upstream and downstream of the solid CO 2 substrate using resonance fluorescence by monitoring the unresolved 130.3 nm triplet transition 3 S 1 − 3 P 2,1,0 at the two fixed points. CO 2 formed was determined by measuring the β activity from C 14 O 2 produced from CO containing C 14 O as a reactant gas. The CO 2 formation was found to be first order in CO and independent of O atom concentration over the entire range of 4.3 × 10 12 to 1.9 × 10 14 cm −3 and 1.2 × 10 11 to 5.6 × 10 12 cm −3 for CO and O respectively. The first order recombination coefficient, λ CO was found to be 1.4 (±.38) × 10 −5 .