Reactive and inelastic scattering of CO and Ar from Cu (110)
Reactive and inelastic scattering of CO and Ar from Cu (110)
Supersonic molecular beams of He, H2, Ar and CO have been scattered from a Cu(110) surface. Diffractive elastic scattering of He and H2 was used to demonstrate the resolution, sensitivity and stability of the newly commissioned ultra high vacuum system and the results were in good agreement with those of the recent literature. Angular distributions of scattered CO were clearly separable into the sticking-trapping (S-T) and direct-inelastic (D-I) components. The proportion of molecules scattered into the two channels was monitored with increasing beam translational energy. CO accommodates well at low energies but scatters with increasing efficiency into the inelastic channel especially at total beam energies above 250meV. The D-I channel has properties which conform to the predictions of the cube models. It was shown from scattering distributions and sticking probability measurements that CO dissociated at total energies above 310meV. The results at all temperatures suggested a model where the critical co-ordinates in the potential energy hypersurface are not only the molecule-surface separation (z) but also the rotational angle of the CO molecule. The D-I component of the distributions of CO and Ar scattering were investigated as a function of incidence angle. On the clean surface scattering is characteristic of normal energy exchange via the substrate phonon modes. At low sulphur coverages a significant increase in normal momentum transfer occurs at a normal energy of 50 ± 2meV for both gases. This disappears at higher sulphur coverages. The resonance appears to be mediated by non-ordered adsorbed sulphur. The CO oxidation reaction was carried out by reacting a CO beam with an adsorbed (2x1)-oxygen layer on Cu(110). Reaction probabilities of 10^-2 - 10^-3 and activation energies of 4.5 ± 0.5 and 65 ± 15 kJ/mol were obtained depending on whether a slow or fast reaction occurred. These results are discussed with reference to previous work and suggestions that surface defects and impurities play a major role in the reaction are made.
University of Southampton
1989
Godfrey, Denise Caroline
(1989)
Reactive and inelastic scattering of CO and Ar from Cu (110).
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Supersonic molecular beams of He, H2, Ar and CO have been scattered from a Cu(110) surface. Diffractive elastic scattering of He and H2 was used to demonstrate the resolution, sensitivity and stability of the newly commissioned ultra high vacuum system and the results were in good agreement with those of the recent literature. Angular distributions of scattered CO were clearly separable into the sticking-trapping (S-T) and direct-inelastic (D-I) components. The proportion of molecules scattered into the two channels was monitored with increasing beam translational energy. CO accommodates well at low energies but scatters with increasing efficiency into the inelastic channel especially at total beam energies above 250meV. The D-I channel has properties which conform to the predictions of the cube models. It was shown from scattering distributions and sticking probability measurements that CO dissociated at total energies above 310meV. The results at all temperatures suggested a model where the critical co-ordinates in the potential energy hypersurface are not only the molecule-surface separation (z) but also the rotational angle of the CO molecule. The D-I component of the distributions of CO and Ar scattering were investigated as a function of incidence angle. On the clean surface scattering is characteristic of normal energy exchange via the substrate phonon modes. At low sulphur coverages a significant increase in normal momentum transfer occurs at a normal energy of 50 ± 2meV for both gases. This disappears at higher sulphur coverages. The resonance appears to be mediated by non-ordered adsorbed sulphur. The CO oxidation reaction was carried out by reacting a CO beam with an adsorbed (2x1)-oxygen layer on Cu(110). Reaction probabilities of 10^-2 - 10^-3 and activation energies of 4.5 ± 0.5 and 65 ± 15 kJ/mol were obtained depending on whether a slow or fast reaction occurred. These results are discussed with reference to previous work and suggestions that surface defects and impurities play a major role in the reaction are made.
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Published date: 1989
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Local EPrints ID: 461217
URI: http://eprints.soton.ac.uk/id/eprint/461217
PURE UUID: dbeb8a0f-90e8-44d7-b4a3-3cfd7f7f9a00
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Date deposited: 04 Jul 2022 18:39
Last modified: 04 Jul 2022 18:39
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Author:
Denise Caroline Godfrey
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