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Measurements were made for the rate constant of OH + CO + He at 293 K, and OD + CO + M (M = He, Ar, N2, air, SF6) at 253−343 K. Results were also obtained for OH + CO in a shock tube at 1400−2600 K using OH and CO absorption. A two-channel RRKM model of these and other representative results was constructed, with five adjustable parameters. A systematic optimization method was then employed to produce the best fit of the data and provide predictive k(T,P,D/H) expressions for other conditions.

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We measured absolute rate coefficients for the reactions of the hydroxyl radical with methane (kl) and methaned4 (k2) using the laser photolysis/laser-induced fluorescence technique. We characterized kl 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 kl at lower temperatures by Vaghjiani and Ravishankara.The measured rate coefficients, in the units cm3 molecule-' s-l, fit well to the three-parameter expressions k l ( T ) = 9.65 X lO-2OP1.58 exp(-1082/T) and k2(79 = 8.70 X 10-22T3.23 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.