Photolysis of Carbon Dioxide at 1633 Å

Abstract

The photolysis of CO₂ at 1633 Å has been re‐examined with particular emphasis on the material balance of the products over the range of reactant pressure from 10 to 760 torr. The products observed included CO, O₂ and O₃; the latter has been identified by infrared and ultraviolet absorption and by the iodometric technique. At high CO₂ pressure a reasonable material balance is obtained from the observed yields of CO, O₂, and O₃, while at low pressures surface reactions appear to be important in an unconditioned vessel. The presence of water vapor has been shown to change the product distribution substantially, with O₂ becoming more important and O₃ less important. The observations made provide potential explanation for the discordant previous results in the literature. The over‐all reaction mechanism is discussed in terms of an initial photolytic formation of O(¹D₂) atoms and their rapid deactivation to O(³P) in collisions with CO₂. The reactions, $\mathrm{H}+{\mathrm{O}}_3\to \mathrm{OH}+{\mathrm{O}}_2$ and $\mathrm{OH}+\mathrm{O}\to \mathrm{H}+{\mathrm{O}}_2$ , are tentatively suggested to account for the catalyzed chain decomposition of ozone in the presence of water vapor.