Deuterium fractionation in dense interstellar clouds

Journal Article · Mon May 01 04:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/167444· OSTI ID:5642674

Millar, T J; Bennett, A; Herbst, E ^[1]

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1. Univ. of Manchester Institute of Science and Technology (England)

The time-dependent gas-phase chemistry of deuterium fractionation in dense interstellar clouds ranging in temperature between 10 and 70 K was investigated using a pseudo-time-dependent model similar to that of Brown and Rice (1986). The present approach, however, considers much more complex species, uses more deuterium fractionation reactions, and includes the use of new branching ratios for dissociative recombinations reactions. Results indicate that, in cold clouds, the major and most global source of deuterium fractionation is H2D(+) and ions derived from it, such as DCO(+) and H2DO(+). In warmer clouds, reactions of CH2D(+), C2HD(+), and associated species lead to significant fractionation even at 70 K, which is the assumed Orion temperature. The deuterium abundance ratios calculated at 10 K are consistent with those observed in TMC-1 for most species. However, a comparison between theory and observatiom for Orion, indicates that, for species in the ambient molecular cloud, the early-time results obtained with the old dissociative recombination branching ratios are superior if a temperature of 70 K is utilized. 60 refs.

• OSTI ID: 5642674
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 340; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHARGED PARTICLES
CHEMICAL COMPOSITION
CHEMISTRY
COMPARATIVE EVALUATIONS
COSMIC GASES
COSMOCHEMISTRY
DEUTERIUM
DISSOCIATION
FLUIDS
FRACTIONATION
GASES
HYDROGEN ISOTOPES
INTERSTELLAR SPACE
IONS
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
MOLECULAR IONS
MOLECULES
NEBULAE
NUCLEI
ODD-ODD NUCLEI
RECOMBINATION
SEPARATION PROCESSES
SPACE
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
TIME DEPENDENCE