Measurement of the rate coefficient for the OH + NO2 reaction under the atmospheric pressure: Its humidity dependence

Humidity dependence of the rate coefficient of the OH + NO2 reaction has been studied. The rate coefficients, measured at the H2O partial pressures ( P H 2 O ) of 29.1 and 3.7 hPa and at 298 K are (1.15 ± 0.02) × 10−11 and (1.40 ± 0.10) × 10−11 cm3 molecule−1 s−1 (±2σ), respectively. The equilibrium constant of the NO2–H2O system estimated using ab initio calculations is too small to explain the retardation of the reaction under our experimental conditions. Thus, we conclude that the NO2–H2O cannot contribute significantly to the OH + NO2 reaction in the atmosphere near the ground surface.