Browsing by Author "Watson, Robert T."

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Kinetic Studies of Diatomic Free Radicals using Mass Spectrometry: Part 1.—System Description and Applications to F Atoms and FO Radicals
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Clyne, Michael A. A.; Watson, Robert T.
A system for sampling of free radicals from a discharge-flow system to a mass spectrometer is described. The molecular radicals FO, ClO, BrO, IO, OH, SF, NF2, and SF2, and the atoms N, O, Br, Cl and F have been detected mass spectrometrically. Methods for the calibration of ion current in terms of absolute concentrations of atoms, and of the radicals FO, ClO and BrO have been developed. The lower concentration limits of detection (signal-to-noise of unity) were: FO, 1 × 1011 cm–3; ClO, 1 × 109 cm–3; BrO, 1.5 × 109 cm–3. The applications of the technique are exemplified by kinetic studies of F 2P atoms and FO X2II radicals, and the following rate constants are reported (298 K): FO + FO [graphic omitted] 2F + O2; ΔU°298=– 68 kj mol–1(1), k1=(8.5 ± 2.8)× 10–12 cm3 molecule–1 s–1. F + NF2+ M [graphic omitted] NF3+ M; ΔU°298=– 253 kj mol–1k2=(8.9 ± 3.3)× 10–3 1 cm6 molecule–2 s–1.
Kinetic studies of diatomic free radicals using mass spectrometry: Part 2.—Rapid bimolecular reactions involving the ClO X2Πradical
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Clyne, Michael A. A.; Watson, Robert T.
The kinetics of rapid bimolecular reactions involving ClO, X2Π, v= 0, radicals at 298 K have been studied mass spectrometrically using molecular beam sampling from a discharge-flow system. The following rate constants (298 K, cm3 molecule–1 s–1) are reported: [graphic omitted] ClO radicals were found to be unreactive towards a range of singlet ground state molecules, up to 670K. The reactions (1) and (2) are important rate-determining steps in the proposed ClOx cycle for depletion of ozone in the stratosphere. The implications for this ClOx cycle of recent measurements of rate constants involving Cl, ClO and OClO, are discussed.
Kinetic Studies of Diatomic Free Radicals Using Mass Spectrometry: Part 4.—The Br + OClO and BrO + ClO reactions
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (09), 1977) Clyne, Michael A. A.; Watson, Robert T.
In a kinetic study of the reaction of ground state Br 2P[fraction three-over-two] bromine atoms with chlorine dioxide, it has proved possible to determine not only the rate constant k–1a for the primary reaction, but also the rate constants k1a, k1b, for the various reactions of ClO with BrO radicals via different channels (1a) and (1b). The rate constants (cm3 molecule–1 s–1 at 298 K; error = 1.5σ) were as follows: [graphic omitted] The reaction kinetics were studied in a flow system using collision-free sampling of free radicals and stable molecules to a mass spectrometer. The thermochemistry and reaction kinetics of the XO + XO reactions (X = Cl, Br) are discussed. The ClO + ClO, BrO + BrO and BrO + ClO reactions are all thought to occur via related free radical channels, XO + XO ⇌ X + XOO. In addition, the ClO + ClO and BrO + ClO reactions occur through a similar and parallel channel, XO + XO ⇌ X + OXO.