Kinetics of the F+CH4 reaction in the temperature range 184-406 K

The temperature dependence of the rate constant for the F + CH4 reaction has been determined by a competitive method using the F + D-2 reaction as a reference reaction. Ratios of rate constants k(F+CH4)/k(F+D2), were determined by a discharge-flow-mass spectrometric technique at eight temperatures in the range 184-406 K. These ratios were combined with accurate data for the kinetic isotope effect k(F+H2)/k(F+D2) to Obtain ratios of rate constants k(F+CH)/k(F+H2), which were then multiplied by recommended values for k(F+H2) to Obtain absolute values for k(F+CH4). The ratios of rate constants k(F+CH4)/k(F+D2) and k(F+CH4)/k(F+H2) and the absolute rate constant k(F+CH4) follow linear Arrhenius dependences over the whole temperature range of the experiments, corresponding to the expressions k(F+CH4)/k(F+D2) = (1.21 +/- 0.04) exp[420 +/- 10)/T], k(F+CH4)/k(F+H2) = (1.16 +/- 0.04) exp[(235 +/- 10/T] and k(F+CH4) = (1.64 +/- 0.05) x 10(-10) exp[-(265 +/- 10)/T] cm(3)/(molecule s). The present results of relative and absolute rate constants are compared with previous literature data.