FEATURES OF THE LOWEST SINGLET AND TRIPLET POTENTIAL-ENERGY SURFACES OF CO3

Portions of the lowest singlet and triplet potential energy surfaces f or the following reactions of oxygen atoms with carbon dioxide: O(1D) + CO2(1SIGMA(g)+) --> O(3P) + CO2(1SIGMA(g)+), --> O2(1DELTA(g)) + CO( 1SIGMA+), --> O2(3SIGMA(g)-) + CO(1SIGMA+) and O(3P) + CO2(1SIGMA(g)+) --> O2(3SIGMA(g)-) + CO(1SIGMA+), were investigated by ab initio self -consistent-field methods with a split valence plus polarization basis set, 6-31G, and with the inclusion of electron correlation by severa l methods. These ab initio results along with earlier experiments sugg est that the predominant reaction pathway leads to a low-lying bound r egion of the singlet potential energy surface. This region involves tw o CO3 intermediates: a D3h structure and a C2v isomer along with the t ransition state joining them. The highest levels of theory considered here support a C2v ring structure for the CO3 intermediate which has b een trapped in earlier experiments. The theoretical vibrational freque ncies are analyzed and compared with experimental results. The bent tr iplet surface, involving cis and trans species, lies approximately 60 kcal/mol above the low-lying singlets. Diatomic products, CO(1SIGMA+) and O2 (3SIGMA(g)- or 1DELTA(g)) are disfavored by a high activation e nergy.