Rate constants for the reactions of the OH radical with NO2 (M=Ar and N2) and SO2 (M=Ar)

Abstract

Absolute rate constants for the reactions OH+NO2+M→HNO3+M (M=Ar, N2) OH+SO2+M→HSO3+M (M=Ar) have been determined at 298°K, using a flash photolysis–resonance fluorescence technique. Rate constants k1 and k2 were determined over the pressure range 25–648 torr for M=Ar, while a rate constant for the first reaction was also obtained for M=N2 at 25 torr total pressure. The low pressure third order rate constants were determined to be k1(M=Ar) = (1.02±0.10) ×10−30 cm6 molecule−2⋅sec−1 and k2(M=Ar) = (1.64±0.33) ×10−31 cm6 molecule−2⋅sec−1, in reasonable agreement with the literature values. The bimolecular rate constants at 760 torr total pressure were determined to be kbi1= (5.9±0.7) ×10−12 cm3 molecule−1⋅sec−1 (M=Ar), kbi1= (6.4±1.0) ×10−12 cm3 molecule−1⋅sec−1 (M=N2), and kbi2= (6.7±0.7) ×10−13 cm3 molecule−1⋅sec−1 (M=Ar). Extrapolation of the data led to limiting high pressure second order constants of k∞1?8.5×10−12 cm3 molecule−1⋅sec−1 and k∞2?8.3×10−13 cm3 molecule−1⋅sec−1.