A Kinetic Study of OH Radical Reactions with Methane and Perdeuterated Methane

Article abstract of DOI:10.1021/j100145a003

We measured absolute rate coefficients for the reactions of the hydroxyl raical with methane (k1) and methane-d4 (k2) using the laser photolysis/laser-induced fluorescence technique.We characterized k1 and k2 over the temperature range 293-800 K at pressures between 400 and 750 Torr of helium.We find excellent agreement between our results and the recent determinations of k1 at lower temperatures by Vaghjiani and Ravishankara.The measured rate coefficients, in the units cm³ molecule^-1 s^-1, fit well to the three-parameter expressions k1(T)=9.65*10^-20T^2.58 exp(-1082/T) and k2(T)=8.70*10^-22T^3.23 exp(-1334/T).The kinetic isotope effect for abstraction of the H and D atoms varies from 6.75 at 293 K to 1.96 at 800 K.We compare our results to recently reported calculations by Melissas and Truhlar.