Studies of reactions of atoms in a discharge flow stirred reactor. Part 3.—The O + H2+ O2 system

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.