A supersonic molecular beam study of activated absorption : H2 on Cu (110) and related reactions
A supersonic molecular beam study of activated absorption : H2 on Cu (110) and related reactions
The initial dissociative sticking probability of hydrogen and deuterium on Cu(110) has been shown to be much lower than previously believed. Cold-seeded beams have been used to separate the vibrational and translational components. The results indicate that the dissociation barrier is accessed through energy partition in both translational and vibrational degrees of freedom in the impinging hydrogen (deuterium) molecule. The minimum translational energy requirement was determined for both hydrogen in the first excited vibrational state (130 meV) and deuterium in the second excited vibrational state (60 meV) and the results are in good agreement with a 2-D potential energy surface with a barrier of height 0.72 eV. The reaction of hydrogen with a (2x1) O overlayer on Cu(100) has been studied as a function of the beam translational energy and the surface temperature. The rate of water production is undetectably low at normal translational energies of less than 200 meV. Above 200 meV, Langmuir-Hinshelwood type kinetics are observed and the reaction goes to completion. The results suggest that the hydrogen dissociation step can be rate limiting and is insensitive to the oxygen coverage. Once this barrier has been overcome, the surface reaction exhibits a surface temperature dependence and an activation energy which varies with oxygen coverage in the range 0- 600 meV. The initial dissociation probability of hydrogen on a (1x2) potassium reconstructed Cu(110) surface was measured. The results suggested that the activation barrier was lowered slightly from the clean surface. The TPD measurements indicated that the apparent desorption energy increased with increasing potassium coverage. The results suggest that the pauli repulsive barrier to dissociation is reduced and the well depth increased when potassium is adsorbed on the surface.
University of Southampton
Lamont, Christine Lavinia Anne
1990
Lamont, Christine Lavinia Anne
Lamont, Christine Lavinia Anne
(1990)
A supersonic molecular beam study of activated absorption : H2 on Cu (110) and related reactions.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The initial dissociative sticking probability of hydrogen and deuterium on Cu(110) has been shown to be much lower than previously believed. Cold-seeded beams have been used to separate the vibrational and translational components. The results indicate that the dissociation barrier is accessed through energy partition in both translational and vibrational degrees of freedom in the impinging hydrogen (deuterium) molecule. The minimum translational energy requirement was determined for both hydrogen in the first excited vibrational state (130 meV) and deuterium in the second excited vibrational state (60 meV) and the results are in good agreement with a 2-D potential energy surface with a barrier of height 0.72 eV. The reaction of hydrogen with a (2x1) O overlayer on Cu(100) has been studied as a function of the beam translational energy and the surface temperature. The rate of water production is undetectably low at normal translational energies of less than 200 meV. Above 200 meV, Langmuir-Hinshelwood type kinetics are observed and the reaction goes to completion. The results suggest that the hydrogen dissociation step can be rate limiting and is insensitive to the oxygen coverage. Once this barrier has been overcome, the surface reaction exhibits a surface temperature dependence and an activation energy which varies with oxygen coverage in the range 0- 600 meV. The initial dissociation probability of hydrogen on a (1x2) potassium reconstructed Cu(110) surface was measured. The results suggested that the activation barrier was lowered slightly from the clean surface. The TPD measurements indicated that the apparent desorption energy increased with increasing potassium coverage. The results suggest that the pauli repulsive barrier to dissociation is reduced and the well depth increased when potassium is adsorbed on the surface.
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Published date: 1990
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Local EPrints ID: 458309
URI: http://eprints.soton.ac.uk/id/eprint/458309
PURE UUID: 0c33ec3b-7c79-46cf-8b0a-a1fe3ff959a1
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Date deposited: 04 Jul 2022 16:46
Last modified: 04 Jul 2022 16:46
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Author:
Christine Lavinia Anne Lamont
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