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Astron. Astrophys. 361, 388-398 (2000)


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Modelling of deuterium chemistry and its application to molecular clouds

H. Roberts and T.J. Millar

Department of Physics, UMIST, P.O. Box 88, Manchester M60 1QD, UK

Received 22 May 2000 / Accepted 4 July 2000

Abstract

We have developed new models of the chemistry of deuterium for investigating fractionation in interstellar molecular clouds. We have incorporated the latest information on reactions which affect deuteration, extended previous models to include S-D bonds for the first time and included the gas-phase chemistry of some doubly-deuterated species. We present models for a wide range of physical parameters, including density, temperature, elemental abundances, and the freeze out of molecules on to dust grains. We discuss the detailed fractionation of particular species and show how fractionation can be used to probe the history of interstellar matter. The freeze out of molecules onto dust leads to significant enhancement in fractionation ratios and, in particular, to large fractionation in doubly-deuterated species.

Key words: ISM: abundances – ISM: molecules – galaxies: abundances – galaxies: ISM – galaxies: Magellanic Clouds

Send offprint requests to: H. Roberts (hhr@janus4.phy.umist.ac.uk)

© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000

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