TEMPERATURE AND PRESSURE-DEPENDENCE OF THE RATE-CONSTANT FOR THE HO2+NO REACTION

The rate constant for the reaction HO2 + NO --> OH + NO2 has been meas ured using the turbulent flow technique with high-pressure chemical io nization mass spectrometry for the detection of reactants and products , At room temperature, the rate constant was found to be independent o f pressure between 70 and 190 Torr of N-2 and given by (8.0 +/- 0.5) x 10(-12) cm(3) molecule(-1) s(-1). The temperature dependence of the r ate constant was investigated between 206 and 295 K; the Arrhenius exp ression over this temperature range is (3.0 +/- 0.4) x 10(-12) exp[(29 0 +/- 30)/T] cm(3) molecule(-1) s(-1). The uncertainties of the room t emperature rate constant and the Arrhenius parameters represent the pr ecision of the data and are reported at the 1 standard deviation level . We estimate that possible systematic errors limit the accuracy of th e determined rate constants to +/- 15%. Comparison of our data with th e results of previous studies indicates that the rate constant for the HO2 + NO --> OH + NO2 reaction does not depend on the inert gas press ure for 295 K greater than or equal to T greater than or equal to 206 K.