The Reaction Kinetics of Amino Radicals with Sulfur Dioxide

Abstract

Abstract Application of the laser photolysis–laser-induced fluorescence method to the reaction NH2 + SO2 in argon bath gas yields pressure-dependent, third-order kinetics which may be summarized as k = (1.49 ± 0.15) × 10−31 (T/298 K)−0.83 cm6 molecule –2 s –1 over 292–555 K, where the uncertainty is the 95% confidence interval and includes possible systematic errors. The quenching of vibrationally excited NH2 is consistent with a high-pressure limit for NH2 + SO2 of (1.62 ± 0.25) × 10−11 cm3 molecule –1 s –1 over the temperature range 295–505 K, where again the 95% confidence interval is shown. Ab initio analysis yields a H2N–SO2 dissociation enthalpy of 73.5 kJ mol –1, and comparison with RRKM theory and the exponential down model for energy transfer yields 〈ΔE〉down = 350 cm –1 for Ar at room temperature.