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Astron. Astrophys. 364, 780-784 (2000)

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Gas-phase formation of doubly-deuterated species

H. Roberts and T.J. Millar

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

Received 12 July 2000 / Accepted 19 October 2000


We present the first results from a time-dependent chemical model to include a gas-phase reaction scheme for producing doubly-deuterated species. Under normal conditions the formation of these species is inefficient. However, when the effects of the freeze out of gas phase species onto grains is included in the chemistry we find that the fractionation of both singly and doubly deuterated species is enhanced.

We compare the predictions from our models with recent observations of deuterated molecules in L134N and find that, contrary to previous expectations, we can reproduce the observed levels of fractionation without recourse to an active grain-surface chemistry.

Key words: ISM: abundances – ISM: molecules – ISM: clouds – ISM: individual objects: LI34N

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

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001