KINETICS AND PRODUCT BRANCHING RATIOS FOR THE REACTION HCO+NO2

The kinetics and product branching of the HCO + NO2 reaction have been studied at room temperature using laser flash kinetic spectroscopy and modeled with microcanonical variational RRKM theory. The rate constant for the disappearance of HCO radical at 296 K is (5.7 +/- 0.9) x 10(-11) cm(3) molecule(-1) s(-1), and it is independent of the pressure of SF6 buffer gas up to 700 Torr. The CO2 yield is 52 +/- 14%. Less than 10% of the reaction goes through the most exothermic product channel, HNO + CO2. The least exothermic product channel, H + CO2 + NO, is responsible for the remaining CO2. HONO has been observed, though not quantitatively, as a reaction product corresponding to the HONO + CO product channel. It must account for the 48 +/- 14% of reaction which does not yield CO2. The rates of formation of the collision complexes HCO(ONO) and HCO(NO2) are calculated by variational RRKM theory to be comparable and only weakly temperature dependent. Branching ratios for the decomposition of these complexes are also calculated. They are found to match most experimental observations from 300 to 1600 K.