Rate coefficient measurements of the reaction CH3+O-2=CH3O+O

Rate coefficients for the reaction CH3 + Oz = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O-2-Ar mixtures using hydrox yl and methyl radical diagnostics. The rate coefficients are well represent ed by an Arrhenius expression given as k = (1.60(-0.47)(+0.67)) x 10(13) ex p(-15813 +/- 587 K/T) cm(3) mol(-1) s(-1). This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the ra te coefficients that has been reported in recent determinations. All measur ements to date, including the present study, have been to some extent affec ted by secondary reactions. The complications due to secondary reactions, c hoice of thermochemical data, and shock-boundary layer interactions that af fect the determination of the rate coefficients are examined.