Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2012-01-20
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
Accepted for publication in MNRAS
Scientific paper
The association reaction S + CO {\to} OCS + hnu has been identified as being particularly important for the prediction of gas-phase OCS abundances by chemical models of dark clouds. We performed detailed ab-initio calculations for this process in addition to undertaking an extensive review of the neutral-neutral reactions involving this species which might be important in such environments. The rate constant for this association reaction was estimated to be several orders of magnitude smaller than the one present in current astrochemical databases. The new rate for this reaction and the introduction of other processes, notably OH + CS {\to} OCS + H and C + OCS {\to} CO + CS, dramatically changes the OCS gas-phase abundance predicted by chemical models for dark clouds. The disagreement with observations in TMC-1 (CP) and L134N (N), suggests that OCS may be formed on grain surfaces as is the case for methanol. The observation of solid OCS on interstellar ices supports this hypothesis.
Bergeat Astrid
Halvick Philippe
Hickson Kevin M.
Loison Jean-Christophe
Wakelam Valentine
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