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Insights on molecular growth pathways in Titan’s ionosphere through combined experimental and theoretical studies of the C2H2N+ + C2H4 ion-neutral reaction
Stockholm University, Faculty of Science, Department of Physics.
(English)In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798Article in journal (Refereed) Submitted
Abstract [en]

The gas phase reactivity of C2H2N+ with C2H4 is studied using a combined experimental and theoretical approach through guided ion beam mass spectrometry (GIB-MS) and ab initio calculations. Results indicate the formation of C3H5+, C2H4+, C4H5N+ and C3H3+ as major products, in addition to minor generation of C2H3+, C2H4N+, C4H4N+, C3H2N+, and CH3+. Theoretical calculations show that reaction proceeds via formation and subsequent rearrangements of a [C4H6N]+ adduct. In the quest to probe its singlet electronic state hypersurface, the most relevant stationary points along the reaction pathway leading to the various products are located and optimized. The results of our calculations at the MP2/6-311++G(d,p) level were found to be in agreement with our experimental findings, as well as with the derived enthalpies of reaction for the designated reaction channels. The present study provides substantial new insights on the formation of complex organics in Titan’s ionosphere detected by the Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft. These pathways might also be of relevance for the generation of long chain carbon-nitrogen bearing compounds in low-temperature environments e.g. the interstellar medium or circumstellar envelopes.

Keywords [en]
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-167166OAI: oai:DiVA.org:su-167166DiVA, id: diva2:1297697
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-03-21Bibliographically approved
In thesis
1. Synthesis of complex organics via molecular growth mechanisms: Combined experimental and theoretical studies on ion-neutral reactions of C2H2N+ with ubiquitous hydrocarbons in Titan's ionosphere
Open this publication in new window or tab >>Synthesis of complex organics via molecular growth mechanisms: Combined experimental and theoretical studies on ion-neutral reactions of C2H2N+ with ubiquitous hydrocarbons in Titan's ionosphere
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To provide insights on the molecular growth mechanisms leading to large carbon and nitrogen-bearing species in Titan’s ionosphere, laboratory measurements of ion-neutral reactions were conducted and the results are presented in the following doctoral dissertation. The product ions of the C2H2N+ reactions with saturated and unsaturated neutral hydrocarbons have been investigated using Guided Ion Beam Mass Spectrometer (GIB-MS). The data have been used to reveal the dependence of product ion intensity on pressure and also with respect to collision energy variations to derive useful insights on the nature of chemical reactions leading to the observed species. Complementary theoretical calculations have been also carried out to assist in interpretation of these measurements and to elucidate the reaction schemes. This study provides comprehensive insights on the formation of long chain and heavy carbon-nitrogen bearing species through exothermic and barrierless ion-neutral reactions which are likely to play a significant role in the formation routes of heavy positive ions of interest, which have been detected in Titan’s ionosphere by Cassini’s Ion Neutral Mass Spectrometer (INMS).

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2019. p. 69
Keywords
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Physical Sciences Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-167136 (URN)978-91-7797-702-5 (ISBN)978-91-7797-703-2 (ISBN)
Public defence
2019-06-04, room 132:028, Nordita East Building, Roslagstullsbacken 23, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Available from: 2019-04-26 Created: 2019-03-19 Last updated: 2019-04-26Bibliographically approved

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