THE PHOTOLYSIS OF CO2 AT 1 470 Å

Abstract

The apparatus used to study the photolysis contained a collimating region which minimized the effect of divergent light, and permitted the temperature of the cell and lamp to be controlled separately. Analytical sensitivity was such that conversions less than 0.2% were possible.Although CO and O2 were the only stable products, the CO/O2 ratios were higher than those required by mass balance. The product yields were found to be independent of CO2 pressure and to be linear with irradiation time at 25 °C. At higher temperatures the quantum yields decreased and at 200 °C were no longer linear functions of irradiation time. The O2 yields decreased when CO was added, the effect increasing with temperature. The overall quantum yield was less than unity. Reactions were observed with CH4, H2, and N2O when these were added in small amount. These results indicated the presence of a reactive species, capable of promoting back reactions and of being adsorbed on the walls. A mechanism is suggested which best fits the results and which postulates CO3 as the reactive species.