The gas-phase destruction of interstellar carbon dioxide:: Calculations on the reactions between CO2 and H2 and between CO2 and H

Carbon dioxide is an abundant component of cold interstellar grains, but its gas-phase abundance is not high. To partially explain this low abundance, it has been suggested that gas-phase CO2 is destroyed by reaction with both atomic and molecular hydrogen. Although there are experimental studies concerning the rate of the reaction between CO2 and H, there are no modern experimental studies for the analogous reaction with H-2. In this paper, we report quantum chemical and dynamical research on the reactive systems CO2 + H and CO2 + H-2. Our results for the former are in excellent agreement with experiment and previous theory, while our results for the latter show this reaction to possess an extremely large potential energy barrier, far in excess of the reaction endothermicity.