| dc.description.abstract | The rate constant, k1, for the self-reaction of HO2, HO2 + HO2 --> H2O2 + O2, was investigated in a discharge-flow system at room temperature and low pressures (1-7 torr) of He carrier gas by laser magnetic resonance detection of HO2, OH, and NO2. Three different chemical reactions, F + H2O2, Cl + H2O2, and CH2OH + O2, were used as sources of HO2 Absolute concentrations of HO2 were determined by converting HO2 to OH and NO2, by reaction with NO, and calibrating the system with known concentrations of OH or NO2. The average values for k1 in a phosphoric acid and halocarbon wax-coated flow tube were (1.90 +- sigma = 0.05) X 10^-12 and (1.54 +- sigma = 0.07) X 10^-12 cm3 molecule-1 s-1, respectively, at 295 + 2 K, where the errors represent one standard deviation of the mean. These results indicate some effect from reactor surface coating. The recommended rate constant from this study is k1 = (1.5 +- 0.3) X 10^-12 cm3 molecule-1s-1, where the error is at the 95% confidence level and includes an estimate of systematic errors. This result combined with other recent studies indicates that the reaction has both pressure-independent and pressure-dependent mechanisms. | en_US |
