The reaction kinetics of amino radicals with sulfur dioxide

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)-0.83cm6 molecule-2 s-1 over 292-555K, 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) × 10-11cm3 molecule-1 s-1 over the temperature range 295-505K, 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.