Deuterium enrichment of ammonia produced by surface N+H/D addition reactions at low temperature

The surface formation of NH3 and its deuterated isotopologues – NH2D, NHD2, and ND3 – is investigated at low temperatures through the simultaneous addition of hydrogen and deuterium atoms to nitrogen atoms in CO-rich interstellar ice analogues. The formation of all four ammonia isotopologues is only...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2015-01, Vol.446 (1), p.449-458
Main Authors: Fedoseev, G., Ioppolo, S., Linnartz, H.
Format: Article
Language:English
Subjects:
Ammonia
Atoms & subatomic particles
Deuteration
Deuterium
Deviation
Enrichment
Formations
Hydrogenation
Molecules
Nitrogen
Star & galaxy formation
Statistical distributions
Surface reactions
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Summary:The surface formation of NH3 and its deuterated isotopologues – NH2D, NHD2, and ND3 – is investigated at low temperatures through the simultaneous addition of hydrogen and deuterium atoms to nitrogen atoms in CO-rich interstellar ice analogues. The formation of all four ammonia isotopologues is only observed up to 15 K, and drops below the detection limit for higher temperatures. Differences between hydrogenation and deuteration yields result in a clear deviation from a statistical distribution in favour of deuterium enriched species. The data analysis suggests that this is due to a higher sticking probability of D atoms to the cold surface, a property that may generally apply to molecules that are formed in low temperature surface reactions. The results found here are used to interpret ammonia–deuterium fractionation as observed in pre-protostellar cores.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stu1852