Browsing by Author "Handy, Brian J."

Now showing 1 - 2 of 2

Studies of Reactions of Atoms in a Discharge Flow Stirred Reactor Part 3.—The O + H2 + O2 System
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Campbell, Ian M.; Rogerson, John S.; Handy, Brian J.
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.
Studies of Reactions of Atoms in a Discharge Flow Stirred Reactor: Part 2.—O + H2 4- CO System
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Campbell, Ian M.; Handy, Brian J.
A discharge-flow stirred reaction system has been used to measure the rate constant for the reaction O(3P) + H2 -> OH + H over the temperature range 315-490 K. Below 350 K, carbon monoxide (< 5%) was added to generate the bluish O + CO chemiluminescence, the intensity of which served to measure oxygen atom decay rates. An expression A'i = (3.1 ±0.5) x IO10 exp (-4950 + 300 K/rj dm3 mol-1 s"1 summarised the measurements above 350 K, but sharp positive deviation was found in the Arrhenius plot of ki below this temperature, for which quantum mechanical tunnelling in the transition state provides a likely interpretation. At 425 K in O/H2/N2 or Ar systems with CO mole fractions up to 60%, HCO radicals are syn- synthesised by the combination reaction H + CO+M = HCO+M (19) and destroyed by the reactions H + HCO->H2 + CO O + HCO -> CO + OH O + HCO -> CO2 + H. (20) (21a) (216) In systems where large mole fractions of CO were present, the [H]/[O] ratios were established from the linear increase in the oxygen atom decay rate from entry to exit with increasing additions of nitric oxide, using the O + CO chemiluminescence as indicator. In 27 experiments in N2 carriers and 36 experiments in Ar carriers with 90 < [CO]/[O] < 950 and 0.2 < [H]/[O] < 3, the measured oxygen atom decay parameters were analysed iteratively by computer. Combination of these two types of experimental results yielded £19(M = N2) = (1.44±0.12)x 10s dm6 mob2 s-‘ and Aj9(M = Ar) = (0.97 + 0.09) x 108 dm6 mol'2 s-1 for 425 K, the latter in agreement with temperature extrapolated literature values. A well-defined ratio A = k20fk21 = 2.1+0.3 was also obtained, together with an estimate of B = k2ia/k2i = 0.4±0.2. A simplified collisional model is used to interpret the values of A and B.