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Deuterium enrichment of polycyclic aromatic hydrocarbons by photochemically induced exchange with deuterium-rich cosmic icesThe polycyclic aromatic hydrocarbon (PAH) coronene (C24H12) frozen in D2O ice in a ratio of less than 1 part in 500 rapidly exchanges its hydrogen atoms with the deuterium in the ice at interstellar temperatures and pressures when exposed to ultraviolet radiation. Exchange occurs via three different chemical processes: D atom addition, D atom exchange at oxidized edge sites, and D atom exchange at aromatic edge sites. Observed exchange rates for coronene (C24H12)-D2O and d12-coronene (C24D12)-H2O isotopic substitution experiments show that PAHs in interstellar ices could easily attain the D/H levels observed in meteorites. These results may have important consequences for the abundance of deuterium observed in aromatic materials in the interstellar medium and in meteorites. These exchange mechanisms produce deuteration in characteristic molecular locations on the PAHs that may distinguish them from previously postulated processes for D enrichment of PAHs.
Document ID
20040088798
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sandford, S. A.
(NASA Ames Research Center Moffett Field CA United States)
Bernstein, M. P.
Allamandola, L. J.
Gillette, J. S.
Zare, R. N.
Date Acquired
August 21, 2013
Publication Date
August 1, 2000
Publication Information
Publication: The Astrophysical journal
Volume: 538
Issue: 2 Pt 1
ISSN: 0004-637X
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NAG5-7208
CONTRACT_GRANT: NAG5-4936
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center ARC
NASA Discipline Exobiology

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