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Astron. Astrophys. 332, 695-702 (1998)


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The DCN/HCN abundance ratio in hot molecular cores

J. Hatchell, T.J. Millar and S.D. Rodgers

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

Received 13 November 1997 / Accepted 5 January 1998

Abstract

We have observed the 3-2 transitions of DCN and HC15 N in a number of hot molecular cores previously surveyed by us with the interesting result that the DCN/HCN ratio is low, a few times [FORMULA], in the hot cores. The abundance ratio of DCN/HCN is derived both `on-core' and `off-core' and, in general is larger at the `off-core' positions. Comparision with chemical models of these sources indicates that DCN liberated from evaporated ices can be destroyed rapidly in the hot gas by reaction with atomic hydrogen, which works to reset the the initial DCN/HCN ratio in the ice to the gas-phase atomic D/H ratio. The low DCN/HCN abundance ratio we measure can be reached in less than 104 years, consistent with previous estimates of the core ages, if the activation energy of the reaction is less than 500 K.

Key words: ISM: abundances – ISM: molecules – radio lines: ISM – molecular processes

Send offprint requests to: J. Hatchell (J.Hatchell@umist.ac.uk)

© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998
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