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Fragmentation of anthracene C14H10, acridine C13H9N and phenazine C12H8N2 ions in collisions with atoms
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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2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 40, 21980-21987 p.Article in journal (Refereed) Published
Abstract [en]

We report experimental total, absolute, fragmentation cross sections for anthracene C14H10, acridine C13H9N, and phenazine C12H8N2 ions colliding with He at center-of-mass energies close to 100 eV. In addition, we report results for the same ions colliding with Ne, Ar, and Xe at higher energies. The total fragmentation cross sections for these three ions are the same within error bars for a given target. The measured fragment mass distributions reveal significant contributions from both delayed (>> 10(-12) s) statistical fragmentation processes as well as non-statistical, prompt (similar to 10(-15) s), single atom knockout processes. The latter dominate and are often followed by secondary statistical fragmentation. Classical Molecular Dynamics (MD) simulations yield separate cross sections for prompt and delayed fragmentation which are consistent with the experimental results. The intensity of the single C/N-loss peak, the signature of non-statistical fragmentation, decreases with the number of N atoms in the parent ion. The fragment intensity distributions for losses of more than one C or N atom are rather similar for C14H10 and C13H9N but differ strongly for C12H8N2 where weak C-N bonds often remain in the fragments after the first fragmentation step. This greatly increases their probability to fragment further. Distributions of internal energy remaining in the fragments after knockout are obtained from the MD simulations.

Place, publisher, year, edition, pages
2014. Vol. 16, no 40, 21980-21987 p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-109264DOI: 10.1039/c4cp03293dISI: 000343072800009OAI: oai:DiVA.org:su-109264DiVA: diva2:765558
Note

AuthorCount:16;

Available from: 2014-11-24 Created: 2014-11-17 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Molecular Hole Punching: Impulse Driven Reactions in Molecules and Molecular Clusters
Open this publication in new window or tab >>Molecular Hole Punching: Impulse Driven Reactions in Molecules and Molecular Clusters
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When molecules are excited by photons or energetic particles, they will cool through the emission of photons, electrons, or by fragmenting. Such processes are often thermal as they occur after the excitation energy has been redistributed across all degrees-of-freedom in the system. Collisions with atoms or ions may also lead to ultrafast fragmentation in Rutherford-like scattering processes, where one or several atoms can literally be knocked out of the molecule by the incoming projectile before the energy can be completely redistributed. The resulting fragmentation pathways can in such knockout processes be very different from those in thermal processes.

This thesis covers extensive studies of collisions between ions/atoms and isolated Polycyclic Aromatic Hydrocarbon (PAH) molecules, isolated fullerene molecules, or clusters of these. The high stabilities and distinct fragmentation channels make these types of molecules excellent test cases for characterizing knockout-driven fragmentation and the reactions that these processes can lead to. I will present experimental measurements for a wide range of energies and compare them with my own molecular dynamics simulations and quantum chemical calculations. In this thesis, I present an in-depth study of the role of knockout in the energetic processing of molecules and clusters. The competition between knockout and thermally driven fragmentation is discussed in detail.

Knockout-driven fragmentation is shown to result in exotic fragments that are far more reactive than the intact parent molecules or fragments from thermal processes. When such reactive species are formed within molecular clusters efficient molecular growth can take place on sub-picosecond timescales. The cluster environments are crucial here because they protect the newly formed molecules by absorbing excess energy. This is a possible pathway for the growth of large PAHs, fullerenes, and similar carbonaceous complexes found in, for instance, the interstellar medium.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2016. 74 p.
Keyword
PAHs, Fullernes, Reactions, Clusters, Interstellar Medium, Fragmentation, Non-Statistical Fragmentation, Collisions, Experiments, Molecular Dynamics, Density Functional Theory
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-129523 (URN)978-91-7649-436-3 (ISBN)
Public defence
2016-06-10, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: Submitted.

Available from: 2016-05-18 Created: 2016-04-25 Last updated: 2017-02-17Bibliographically approved

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Stockett, Mark H.Gatchell, MichaelAlexander, John D.Chen, TaoKulyk, KostiantynSchmidt, Henning T.Zettergren, HenningCederquist, Henrik
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