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Oxygen fractionation in dense molecular clouds.


ABSTRACT: We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O2, and SO2. This large effect is due to the efficiency of the neutral 18O + NO, 18O + SO, and 18O + O2 exchange reactions. The modeling results were compared to new and existing observed isotopic ratios in a selection of cold cores. The good agreement between model and observations requires that the gas-phase abundance of neutral oxygen atoms is large in the observed regions. The S16O/S18O ratio is predicted to vary substantially over time showing that it can be used as a sensitive chemical proxy for matter evolution in dense molecular clouds.

SUBMITTER: Loison JC 

PROVIDER: S-EPMC6699989 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O<sub>2</sub>, and SO<sub>2</sub>. This large effect is due to the efficiency of the neutral <sup>18</sup>O + NO, <sup>18</sup>O + SO, and <sup>18</sup>O + O<sub>2</sub> exchange reactions. The modeling results were compare  ...[more]

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