Abstract:
By addition of H2 to O(3P) atoms in N2 carrier, a partial conversion of O atoms to H atoms was achieved through the reactions O + H2→ OH + H (1) O + OH → O2+ H (2) in a discharge-flow stirred reactor at 425 K. Addition of small amounts of CO (< 5 %) generated bluish O + CO chemiluminescence, the intensity of which at entry and exit ports was measured to establish O atom decay rates. When O2(< 1 %) was added, HO2 radicals were formed in situ by reaction H + O2+ M → HO2+ M (9) and the O atom decay rate was accelerated due to subsequent reactions H + HO2→ 2OH (10) O + HO2→ OH + O2(11) and reaction (2). The parallel steps to reaction (10) H + HO2→ H2+ O2(22) H + HO2→ H2O + O (23) consume H atoms and reaction (23) produces O atoms so decreasing the catalytic rate of removal of O atoms. From the variation of the catalytic rate as a function of [H]/[O] ratios in the range 0.16 to 3.46, a value of k9(M = N2)=(1.2 ± 0.2)× 1010 dm6 mol–2 s–1 at 425 K was obtained, together with a placing of the ratio k11/(k10+k22+k23)(i.e. the relative reactivity of HO2 with O and H atoms) in the range 0.2 to 0.5 at 425 K.
