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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
Stockholm University, Faculty of Science, Department of Physics.
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 [en]
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: urn:nbn:se:su:diva-167136ISBN: 978-91-7797-702-5 (print)ISBN: 978-91-7797-703-2 (electronic)OAI: oai:DiVA.org:su-167136DiVA, id: diva2:1297427
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At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.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
List of papers
1. Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study
Open this publication in new window or tab >>Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study
2016 (English)In: Molecular Astrophysics, ISSN 2405-6758, Vol. 2, p. 1-11Article in journal (Refereed) Published
Abstract [en]

The ion-neutral reactions of the C2H2N+ cation with C2H2 have been investigated using a Guided Ion Beam Mass Spectrometer (GIB-MS). The following ionic products were observed: CH3+, C2H2+, C2H3+, HNC+/HCN+, HCNH+, C3H+, C2N+, C3H3+, HCCNand C4H2N+. Theoretical calculations have been carried out to propose reaction pathways leading to the observed products. These processes are of relevance for the generation of long chain nitrogen-containing species and they may be of interest for the chemistry of Titan’s ionosphere or circumstellar envelopes.

Keywords
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-167125 (URN)10.1016/j.molap.2015.09.002 (DOI)000397267000001 ()
Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-11-05Bibliographically approved
2. Ion-neutral reaction of C2H2N+ with CH4: An experimental and theoretical study
Open this publication in new window or tab >>Ion-neutral reaction of C2H2N+ with CH4: An experimental and theoretical study
Show others...
2016 (English)In: Molecular Astrophysics, ISSN 2405-6758, Vol. 5, p. 9-22Article in journal (Refereed) Published
Abstract [en]

The current study was undertaken to probe the ionic products of the ion-neutral reaction of C2H2N+ with CH4 using guided ion beam mass spectrometry (GIB-MS) in which the CH3+, C2H3+, HCNH+, C2H5+, C2H3N+ and C3H4N+ ions are identified as products. Theoretical calculations were performed to suggest reaction pathways leading to the detected products. These processes might be of relevance for the generation of long chain carbon-nitrogen bearing compounds in Titan's atmosphere, the interstellar medium or circumstellar envelopes.

Keywords
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-142426 (URN)10.1016/j.molap.2016.07.001 (DOI)000397268100002 ()
Available from: 2017-05-02 Created: 2017-05-02 Last updated: 2019-03-27Bibliographically approved
3. Experimental and theoretical investigations of the ion-neutral reaction of C2H2N+ with C2H6 and implications on chain elongation processes in Titan's atmosphere
Open this publication in new window or tab >>Experimental and theoretical investigations of the ion-neutral reaction of C2H2N+ with C2H6 and implications on chain elongation processes in Titan's atmosphere
2016 (English)In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 411, p. 1-13Article in journal (Refereed) Published
Abstract [en]

In this study we report theoretical and experimental evidence for the formation of ionic products by the ion-neutral reaction of C2H2N+ with C2H6. Our investigations consist of laboratory measurements using a guided ion beam mass spectrometer together with complementary ab initio quantum chemical computations, at the MP2/6-311++G(d,p) level of theory, in order to elucidate the energetics and geometries of the intermediates and transition states that are involved in the production of the observed product ions. This study also provides insights on the isomeric nature of the observed product ions, their formation pathways together with collision energy and pressure dependences. The experimental data agrees well with the predictions of the ab initio calculations. Despite data provides evidence for the occurrence of C2H5+ as the most salient product ion, the production of CH3+, C2H3+, C3H5+, C3H7+ and C2H4N+ is also evident. A reaction scheme was proposed to elucidate the mechanisms responsible for the formation of the observed product ions. These processes might be intermediate steps in the generation of long chain carbon and nitrogen-bearing compounds in Titan's ionosphere, the interstellar medium or circumstellar envelopes.

Keywords
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-139420 (URN)10.1016/j.ijms.2016.10.003 (DOI)000390969200001 ()
Available from: 2017-02-27 Created: 2017-02-27 Last updated: 2019-03-20Bibliographically approved
4. Insights on molecular growth pathways in Titan’s ionosphere through combined experimental and theoretical studies of the C2H2N+ + C2H4 ion-neutral reaction
Open this publication in new window or tab >>Insights on molecular growth pathways in Titan’s ionosphere through combined experimental and theoretical studies of the C2H2N+ + C2H4 ion-neutral reaction
(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
Astrochemistry, Complex molecules, Ion-neutral reactions, Mass spectrometry, Planetary and satellite atmospheres, Titan
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-167166 (URN)
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-03-21Bibliographically approved

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