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The photochemistry of carbon-rich circumstellar shellsThe effect of ambient ultraviolet photons on the chemical structure of carbon-rich, circumstellar envelopes is investigated with a simple formulation of the time-dependent, photochemical rate equations valid for optically thick shells. Molecules injected into the shielded inner envelope are broken down when they reach the outer regions where ambient ultraviolet photons can penetrate. A quantitative description of the abundance variations is obtained for the case of uniform expansion by detailed consideration of the shielding of the radiation by the dust and molecules of the envelope. Representative results are presented to illustrate the role of shielding in defining the extent of molecular envelopes, the formation of C I and C II shells by photodestruction of carbon-bearing molecules, and the development of layered chemical structures from the photobreakup of polyatomic molecules. Photochemistry makes the outer parts of thick, carbon-rich envelopes into complex regions containing radicals, ions, and atoms which are of considerable observational and theoretical interest.
Document ID
19820038021
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Huggins, P. J.
(New York Univ. New York, NY, United States)
Glassgold, A. E.
(New York University New York, NY, United States)
Date Acquired
August 10, 2013
Publication Date
January 1, 1982
Publication Information
Publication: Astrophysical Journal
Subject Category
Astrophysics
Accession Number
82A21556
Funding Number(s)
CONTRACT_GRANT: NGR-33-016-196
Distribution Limits
Public
Copyright
Other

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