The molecular composition of dense interstellar clouds
Presented in this paper is an ab initio chemical model for dense interstellar clouds that incorporates 598 grain surface reactions, with small grains providing the reaction area. Gas-phase molecules are depleted through collisions with grains. The abundances of 372 chemical species are calculated as a function of time and are found to be of sufficient magnitude to explain most observations. Peak abundances are achieved on time scales on the order of 10/sup 5/--10/sup 6/ years, depending on cloud density and kinetic temperature. The reaction rates for ion-molecule chemistry are approximately the same, indicating that surface and gas-phase chemistry may be coupled in certain regions. The composition of grain mantles is shown to be a function of grain radius. In certain grain size ranges, large molecules containing two or more heavy atoms are more predominant than lighter ''ices''-H/sub 2/O, NH/sub 3/, and CH/sub 4/. It is possible that absorption due to these large molecules in the mantle may contribute to the observed 3..mu..m band in astronomical spectra.
- Research Organization:
- Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology
- OSTI ID:
- 7309380
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 212:2; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
COLLISIONS
COSMIC GASES
COSMOLOGICAL MODELS
FLUIDS
GASES
INTERSTELLAR GRAINS
INTERSTELLAR SPACE
ION COLLISIONS
ION-MOLECULE COLLISIONS
MATHEMATICAL MODELS
MOLECULE COLLISIONS
MOLECULES
PARTICLES
SPACE