Volume 391, Number 2, August IV 2002
|Page(s)||681 - 687|
|Published online||02 August 2002|
Dark cloud chemistry in initially H-rich regions
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, England
2 Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, England
3 Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT, England
Corresponding author: J. M. C. Rawlings, email@example.com
Accepted: 2 June 2002
The chemistry in dark regions of dense cores is explored as a function of the initial abundance ratio of H to H2, on the assumption that some cores form on a timescale and are younger than the time required for the H:H2 ratio to attain its equilibrium value. Observational diagnostics of non-equilibrium values of the initial H:H2 ratio are identified. In initially H-rich material, the abundances of OH, NH3, CN, and HNC are for some time higher than they are in initially H-poor material. In initially H-poor regions, the abundances of CO, species containing multiple carbon atoms in each molecule, and CS are larger for an (observationally significant) period than in initially H-rich material.
Key words: ISM: clouds / ISM: molecules / astrochemistry / molecular processes
© ESO, 2002
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