An experimental and theoretical study of the product distribution of the reaction CH2 ((X)over-tilde 3B1)+NO

Measurements of the product branching ratios of the reaction CH2 ((X) over tilde B-3(1)) + NO (1) are presented together with calculations of the thermal rate constant and branching ratios using unimolecular rate theory. The reaction was investigated experimentally at room temperature using FTIR spectroscopy. The yields of the main products HCNO and HCN were found to be Gamma (HCNO) = 0.89 +/- 0.06, Gamma (HCN) = 0.11 +/- 0.06. Other minor products could be rationalized by numerical simulations of the reaction system taking into account possible consecutive reactions. The potential energy surface for the reaction was characterized by quantum chemical calculations using ab initio and density functional methods. The proposed reaction pathways connecting reactants to products were explored by multi-channel unimolecular rate theory calculations to determine the CH2 ((X) over tilde) + NO capture rate constant and the rate constants for the different product channels as a function of temperature. The calculated capture rate constant of k = 2.3 x 10(13) cm(3) mol(-1) s(-1) is in good agreement with experimental values at room temperature. Collisional stabilization of the initial H2CNO recombination complex was predicted to be negligible up to pressures of >1 bar. For ambient pressures and temperatures up to 2000 K, HCNO + H were calculated as the dominating products, with Gamma (HCNO) approximate to 0.94 in agreement with the experiments. The channel to HCN + OH was calculated with 0.015 less than or equal to Gamma (HCN) less than or equal to 0.05 only slightly below the experimental value.