REINVESTIGATION OF RATE COEFFICIENTS FOR O+H2 AND O+CH4

The improved version of the wide-temperature-range, fast-flow reactor with ESR detection employed at this laboratory for a series of atom-molecule rate measurements has been used to reinvestigate the reactions O+H 2ΔOH+H [1] and O+CH ΔOH+CH3 [3] which had been previously measured with the original apparatus. The new data are uniformly lower than before, implying a systematic error in the old results. The revised Arrhenius expressions are k1 = 3.2×1012exp(-10200/ RT) cm3 mole-1,sec-1 valid in the range 500°-900°K, and k3, = 2.0×1013 exp(-9200/RT) over 400°-900°K. The new results are in better agreement with other data in the literature. Our previous measurements on 0+C2H 6ΔOH+C2H5 and O+ D2→OD+D have also been checked and do not require revision.