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

SUBMITTER: Loison JC 

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

REPOSITORIES: biostudies-literature