PRESSURE AND TEMPERATURE-DEPENDENCE OF THE GAS-PHASE REACTION BETWEENMETHYL AND HYDROXYL RADICALS

The kinetics of the reaction CH3+OH(+M)-->CH3OH(+M) was studied in the temperature range 283-373 K and in the pressure range 85-1000 mbar SF 6 by pulse radiolysis combined with UV absorption spectroscopy. The me thyl and hydroxyl radical decays were followed by monitoring the trans ient UV absorption signals at 216.4 nm and 309.0 nm respectively. The reaction was studied in the fall-off region and by Troe's analysis the following high- and low-pressure limiting rate constants were obtaine d: k(rec,infinity) = (8.7 +/- 0.7) x 10(10)(T/300)0.1 M-1 s-1 and k(re c,0/[SF6] = (9.0 +/- 2.4) x 10(14)(T/300)-3.8 M-2 s-1. The low-pressur e limiting rate constant for the OH radical self-reaction was also der ived: k(OH+OH,0)/[SF6]=(4.0 +/- 0.7) x 10(11)(T/300)-1.4 M-2 s-1 using the value of k(OH+OH,infinity = 1.8 x 10(10)(T/300)-0.37 M-1 s-1 for the high-pressure limit.