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An experimental investigation of fractionation by sputter depositionArtificial glass targets composed of elements varying widely in atomic weight were irradiated at an angle of incidence of 45 deg by 2-keV hydrogen ions at a current density of .33 mA/sq cm, and sputtered atoms were caught on a molybdenum film. Analyses of the sputter-deposited films and unsputtered target glasses were carried out by electron microprobe. The backward-sputtered component was found to be enriched in elements of low atomic weight, while the forward-sputtered component was enriched in heavy atoms. These results indicate that at the lunar surface lighter elements and isotopes would tend to be ejected in backward directions, escaping directly through the openings which admit bombarding ions without first striking an adjacent grain surface; heavy elements and isotopes would be forward-sputtered deeper into the soil and be preferentially retained, contributing to the reported enrichments of heavy elements and isotopes. Additional results show that the binding energy of an element in its oxide form influences the sticking coefficient of a sputtered atom; elements of low binding energy are likely to desorb, while elements of high binding energy tend to stick to the first bounce surface.
Document ID
19790055179
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Paruso, D. M.
(Pittsburgh Univ. Pittsburgh, PA, United States)
Cassidy, W. A.
(Pittsburgh Univ. Pittsburgh, PA, United States)
Hapke, B. W.
(Pittsburgh, University Pittsburgh, Pa., United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1978
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Start Date: March 13, 1978
End Date: March 17, 1978
Accession Number
79A39192
Distribution Limits
Public
Copyright
Other

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