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Behavior of molecules on interstellar grains - Application of the Langevin equation and iterative extended HueckelThe Langevin equation was used to explore an adsorbate desorption mechanism. Calculations were performed using iterative extended Hueckel on a silica model site with various small adsorbates, e.g., H, CH, OH, NO, CO. It was found that barriers to free traversal from one site to another are substantial (about 3-10 eV). A bootstrap desorption mechanism for some molecules in the process of forming at a site also became apparent from the calculations. The desorption mechanisms appear to be somewhat balanced by a counterforce - the attraction of sites for the newly desorbed molecule. The order of attraction to a silica grain site for the diatomic molecules considered was OH greater than CH greater than CO greater than NO, when these entities were sufficiently distant. The nature of the silica grain and that of the 'cold' desorption mechanism, when considered together, suggest that the abundance of very small grains might be less common than anticipated.
Document ID
19810034061
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Aronowitz, S.
(NASA Ames Research Center Moffett Field, CA, United States)
Chang, S.
(NASA Ames Research Center Extraterrestrial Research Div., Moffett Field, Calif., United States)
Date Acquired
August 11, 2013
Publication Date
November 15, 1980
Publication Information
Publication: Astrophysical Journal
Subject Category
Astrophysics
Accession Number
81A18465
Funding Number(s)
CONTRACT_GRANT: NASA ORDER A-51416-B
Distribution Limits
Public
Copyright
Other

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