A KINETIC-STUDY OF THE REACTION BETWEEN ETHYLPEROXY RADICALS AND HO2

Flash photolysis-time-resolved UV spectroscopy is used to measure the rate constant for the C2H5O2 + HO2 reaction over the temperature range of 210-363 K. The radicals are generated by photolysis of F-2 in the presence of H-2 and ethane. The rate constant for the F+ C2H6 reaction is measured relative to the F + H-2 reaction to be k(1) = (7.1(-1.6)(+21)) X 10(-10) e((-347+/-69)/T) cm(3) s(-1). In order to ascertain time-resolved concentrations, the HO2 UV absorption cross section and its self-reaction rate constant have been remeasured. The UV cross section is in good agreement with previous reports, with sigma(max) = 0.041 Angstrom(2) at 203 nm. The self-reaction rate constant of k(5) = (2.8+/-0.5) X 10(-13) e((594+/-55)/T) cm(3) s(-1) is in excellent agreement with the currently recommended value. The rate constant for the C2H5O2 + HO2 reaction is k(7) = (6.9(-1.6)(+2.1)) X 10(-13) e((702+/-69)/T) cm(3) s(-1). This result is discussed with regard to the discrepancy which exists between the two previous measurements of this rate constant.