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Adsorption and recombination of hydrogen atoms on a model graphite surfaceThe adsorption and recombination of atomic hydrogen on a model graphite grain have been examined in a series of calculations in which a modified, iterative, extended Hueckel program was used. The hydrogen atom is found to be chemisorbed at a site with a zero-point binding energy of 0.7 eV and at an equilibrium distance of 2.25 A above the site. Despite a barrier of about 0.4 eV between adjacent sites, calculations suggest that at temperatures as low as 10 K, an H atom will tunnel through to adjacent sites in less than one nanosecond. However, a potential barrier to the recombination of two hydrogen atoms has been found which displays high sensitivity to the mutual arrangement of the two hydrogen atoms with respect to the graphite surface. Results show that at very low temperatures, recombinations can occur only by tunneling. Consistent with experiment, the region in which H2 begins to form exhibits a repulsive potential with respect to possible chemisorption of the incipient H2 entity.
Document ID
19850054872
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Aronowitz, S.
(Fairchild Research Center Palo Alto, CA, United States)
Chang, S.
(NASA Ames Research Center Extraterrestrial Research Div., Moffett Field, CA, United States)
Date Acquired
August 12, 2013
Publication Date
June 1, 1985
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 293
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
85A37023
Distribution Limits
Public
Copyright
Other

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