FTIR PRODUCT STUDY OF THE REACTIONS CH3O2-3(CH3O2 AND CH3O2+O)

The products of the self-reaction of methylperoxy radicals have been d etermined at 296 K in a 140-L chamber using continuous ultraviolet pho tolysis with FTIR detection. The branching fraction for the reaction c hannel giving methoxy radicals is found to be (41 +/- 4)%, in good agr eement with two earlier studies but somewhat higher than the most rece nt investigations. No evidence was found for the production of CH3OOCH 3 (yield <6%). The addition of ozone led to changes in the rates of fo rmation of the major products, which could largely be explained by che mistry of the OH radical. However, some evidence was found for a slow reaction of CH3O2 With O-3 occurring with a rate coefficient of 1 x 10 (-17) cm(3) molecule(-1) s(-1), with an uncertainty of a factor of 2. As part of the present work a relative rate technique was used to meas ure k(Cl + CH3N2CH3) = (4.8 +/- 0.6) x 10(-11) cm(3) molecule(-1) s(-1 ) at 296 K. The decay of peroxy radical concentrations in the nighttim e clean troposphere is interpreted in terms of the product branching r atios and the rate coefficient for the reaction of CH3O2 + O-3.