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The Dissociative Recombination of Protonated Acrylonitrile, CH2CHCNH+, with implications for the Nitrile Chemistry in Dark Molecular Clouds and the Upper Atmosphere of Titan
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 695, no 1, 317-324 p.Article in journal (Refereed) Published
Abstract [en]

Measurements on the dissociative recombination (DR) of protonated acrylonitrile, CH2CHCNH+, have been performed at the heavy ion storage ring CRYRING located in the Manne Siegbahn Laboratory in Stockholm, Sweden. It has been found that at similar to 2meV relative kinetic energy about 50% of the DR events involve only ruptures of X-Hbonds (where X = C or N) while the rest leads to the production of a pair of fragments each containing two heavy atoms (alongside H and/or H-2). The absolute DR cross section has been investigated for relative kinetic energies ranging from similar to 1 meV to 1 eV. The thermal rate coefficient has been determined to follow the expression k(T) = 1.78 x 10(-6) (T/300)(-0.80) cm(3) s(-1) for electron temperatures ranging from similar to 10 to 1000 K. Gas-phase models of the nitrile chemistry in the dark molecular cloud TMC-1 have been run and results are compared with observations. Also, implications of the present results for the nitrile chemistry of Titan's upper atmosphere are discussed.

Place, publisher, year, edition, pages
2009. Vol. 695, no 1, 317-324 p.
Keyword [en]
ISM: clouds, ISM: molecules, methods: laboratory, molecular processes
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:su:diva-43004DOI: 10.1088/0004-637X/695/1/317ISI: 000264779500027OAI: oai:DiVA.org:su-43004DiVA: diva2:352902
Available from: 2010-09-23 Created: 2010-09-23 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Dissociative recombination of organic molecular ions of relevance for interstellar clouds and Titan's upper atmosphere
Open this publication in new window or tab >>Dissociative recombination of organic molecular ions of relevance for interstellar clouds and Titan's upper atmosphere
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents experimental studies on the dissociative recombination (DR) of the organic molecular ions CD3CND+, CH2CHCNH+, CH3CH2CNH+, CD3CDO+, CH3CHO+ and DCOOD2+. The experiments were all performed at the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm, Sweden. DR is the process in which a singly charged molecular cation captures a free electron, forming a highly excited intermediate molecule which then dissociates into exclusively neutral fragments. The process plays an important role as a plasma neutralizing mechanism in many cold, low density plasmas such as those encountered in planetary ionospheres and interstellar clouds. DR can also act as the final step in the gas-phase synthesis of different neutral molecules in such environments.

Our experimental findings indicate that nitriles that are lost by protonation in Titan’s upper atmosphere or in interstellar clouds to a large extent may be recycled by DR. Also, it appears that the DR of nitrile ions does not break the C-N bond, which supports the hypothesis that nitriles which are formed in Titan’s upper atmosphere do not degrade to recover N2. For the studied acetaldehyde cations, CD3CDO+ and CH3CHO+, we observed a considerable isotopic effect in the cross section, with the lighter isotopologue being more reactive. In the DR of DCOOD2+ an upper limit of only 13% for the branching fraction of the DCOOD + D channel was found. This finding has pronounced effects on the predicted abundance of formic acid in dark clouds.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2010. 70 p.
Keyword
Dissociative recombination, Astrochemistry
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-43372 (URN)978-91-7447-133-5 (ISBN)
Public defence
2010-11-26, sal FB42, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2010-11-03 Created: 2010-10-11 Last updated: 2010-10-26Bibliographically approved

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Vigren, ErikHamberg, MathiasZhaunerchyk, VitaliThomas, Richard D.Larsson, MatsGeppert, Wolf D.
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