Reference : Ortho-to-para abundance ratios of NH2in 26 comets: implications for the real meaning ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/203436
Ortho-to-para abundance ratios of NH2in 26 comets: implications for the real meaning of OPRs
English
Shinnaka, Yoshiharu [> >]
Kawakita, Hideyo [> >]
Jehin, Emmanuel mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa) >]
Decock, Alice [> >]
Hutsemekers, Damien mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Manfroid, Jean mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
1-Nov-2016
Monthly Notices of the Royal Astronomical Society
Blackwell Publishing
462
S124-S131
Yes (verified by ORBi)
International
0035-8711
1365-2966
Oxford
United Kingdom
[en] Abundance ratios of nuclear-spin isomers for cometary molecules having identical protons, such as water and ammonia, have been measured and discussed from the viewpoint that they are primordial characters in comet. In the case of ammonia, its ortho-to-para abundance ratio (OPR) is usually estimated from OPRs of NH2 because of difficulty in measuring OPR of ammonia directly. We report our survey for OPRs of NH2 in 26 comets. A weighted mean of ammonia OPRs for the comets is 1.12 ± 0.01 and no significant difference is found between the Oort Cloud comets and the Jupiter-family comets. These values correspond to ∼30 K as nuclear-spin temperatures. The OPRs of ammonia in comets probably reflect the physicochemical conditions in coma, rather than the conditions for the molecular formation or condensation in the pre-solar molecular cloud/the solar nebula, based on comparison of OPRs (and nuclear-spin temperatures) of ammonia with those of water, 14N/15N ratios in ammonia, and D/H ratios in water. The OPRs could be reset to a nuclear-spin weights ratio in solid phase and modified by interactions with protonated ions like H3O+, water clusters (H2O)n, ice grains, and paramagnetic impurities (such as O2 molecules and grains) in the inner coma gas. Relationship between the OPRs of ammonia and water is a clue to understanding the real meaning of the OPRs.
Researchers ; Professionals ; Students
http://hdl.handle.net/2268/203436
10.1093/mnras/stw2298
http://adsabs.harvard.edu/abs/2016MNRAS.462S.124S

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