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 + D₂ 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+CH4/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) × 10¹⁰ exp[-(265 ± 10)/T] cm³/(molecule s). The present results of relative and absolute rate constants are compared with previous literature data.