Reinvestigation of the Rate Coefficients for O + H2 and O + CH4

Abstract

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+H₂ΔOH+H [1] and O+CHΔOH+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 $k_1{\text{\hspace{0.17em}=\hspace{0.17em}3.2\hspace{0.17em}×\hspace{0.17em}10}}^{13}\exp \text{(−\hspace{0.17em}10 200\hspace{0.17em}/\hspace{0.17em}RT)}{\mathrm{cm}}^3{\mathrm{mole}}^{\text{−1}}·{\sec }^{\text{−1}}$ valid in the range 500°–900°K, and $k_3{\text{\hspace{0.17em}=\hspace{0.17em}2.0\hspace{0.17em}×\hspace{0.17em}10}}^{13}\exp \text{(−\hspace{0.17em}9200\hspace{0.17em}/\hspace{0.17em}RT)}$ over 400°–900°K. The new results are in better agreement with other data in the literature. Our previous measurements on O+C₂H₆ΔOH+C₂H₅ and O+D₂→OD+D have also been checked and do not require revision.