Johnson, Peter D. (1978) The interaction of helium metastable atoms with metal surfaces. PhD thesis, University of Warwick.

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Abstract

An investigation has been made of the interaction of helium metastable atoms (2³S and 2¹S) with metal surfaces in different degrees of contamination.

In order to carry out this investigation, an ultra-high vacuum chamber has been constructed enabling the operator to clean the metal surfaces in situ, monitor the state of cleanliness of the surfaces with Auger electron spectroscopy and then perform experiments with a beam of metastable atoms. A new metastable atom source has been built to produce a reasonably intense beam of atoms in the metastable states.

Experiments have been performed on a clean Ni (100) surface and this surface with adsorbed sulphur and oxygen. Further experiments have been performed on a polycrystalline tungsten surface both in the clean state and with adsorbed carbon monoxide. Secondary electron energy distributions resulting from the impact of excited atoms on these surfaces show little agreement with the results to be expected on the basis of presently accepted theories. It is found that, in general, the total yield of secondary electrons increases linearly with coverage.

Extensive comparisons have been made between the experiments reported in this thesis and the results from INS and other experiments with metastable atoms.

These comparisons lead to the conclusion that the interaction of an ion and that of an excited atom with metal surfaces are two different processes. A new model for the de-excitation of the excited atom has been suggested and the results to be expected from such a de-excitation mechanism examined.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Helium, Helium ions, Scattering (Physics), Metals -- Surfaces, Surfaces (Physics), Surface chemistry, Auger effect
Official Date:	March 1978
Dates:	Date Event March 1978 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Delchar, T. A.
Sponsors:	Science Research Council (Great Britain)
Extent:	vi, 123 leaves : illustrations, photographs
Language:	eng

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