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Unimolecular dissociation of anthracene and acridine cations: The importance of isomerization barriers for the C2H2 loss and HCN loss channels
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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2011 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, 084304- p.Article in journal (Refereed) Published
Abstract [en]

The loss of C2H2 is a low activation energy dissociation channel for anthracene (C14H10) and acridine (C13H9N) cations. For the latter ion another prominent fragmentation pathway is the loss of HCN. We have studied these two dissociation channels by collision induced dissociation experiments of 50 keV anthracene cations and protonated acridine, both produced by electrospray ionization, in collisions with a neutral xenon target. In addition, we have carried out density functional theory calculations on possible reaction pathways for the loss of C2H2 and HCN. The mass spectra display features of multi-step processes, and for protonated acridine the dominant first step process is the loss of a hydrogen from the N site, which then leads to C2H2/HCN loss from the acridine cation. With our calculations we have identified three pathways for the loss of C2H2 from the anthracene cation, with three different cationic products: 2-ethynylnaphthalene, biphenylene, and acenaphthylene. The third product is the one with the overall lowest dissociation energy barrier. For the acridine cation our calculated pathway for the loss of C2H2 leads to the 3-ethynylquinoline cation, and the loss of HCN leads to the biphenylene cation. Isomerization plays an important role in the formation of the non-ethynyl containing products. All calculated fragmentation pathways should be accessible in the present experiment due to substantial energy deposition in the collisions.

Place, publisher, year, edition, pages
2011. Vol. 135, 084304- p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-63731DOI: 10.1063/1.3626792OAI: oai:DiVA.org:su-63731DiVA: diva2:452026
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Ionization and Fragmentation of Complex Molecules and Clusters: Biomolecules and Polycyclic Aromatic Hydrocarbons
Open this publication in new window or tab >>Ionization and Fragmentation of Complex Molecules and Clusters: Biomolecules and Polycyclic Aromatic Hydrocarbons
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work deals with ionization and fragmentation of biomolecules and polycyclic aromatic hydrocarbon (PAH) molecules. They are studied in the gas phase both as isolated molecules and as weakly bound clusters. The purpose of the experimental and theoretical investigations are to elucidate charge and energy transfer and related redistribution processes, as well as fragmentation behaviors.

The first part of this thesis presents results from studies on biomolecular ions, in particular nucleotides and peptides, which are primarily examined in electron capture induced dissociation processes. These investigations are relevant for the better understanding of radiation damage to DNA and processes involved in the sequencing of proteins. It is found that the immediate environment have a decisive influence on the fragmentation behaviors. Evaporation of surrounding molecules protect the biomolecules, but their effect on the electronic structure may also enhance or suppress different fragmentation channels.

In the second part of the thesis, results from studies on PAH molecules are presented. Experimentally, their properties are mainly probed through collisions with atomic ion projectiles having kilo-electronvolt kinetic energies. As a widespread pollutant on Earth, and as a family of abundant molecules in space, PAHs are not only relevant from an environmental and health perspective, but they are also important for the understanding of the universe. The present results relate to the stabilities of these molecules, both in isolated form and in clusters, when heated or multiply ionized. It is found to be easier to remove several electrons from clusters of PAH molecules than from isolated PAHs, and fission processes determine their ultimate stabilities. Heated low-charge state clusters of PAHs undergo long evaporation sequences once these have started. For isolated and heated PAHs, internal structural rearrangements are demonstrated to be important in the fragmentation processes.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2011. 168 p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-63733 (URN)978-91-7447-399-5 (ISBN)
Public defence
2011-12-02, lecture room FB53, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
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Available from: 2011-11-10 Created: 2011-10-27 Last updated: 2011-11-01Bibliographically approved

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Johansson, Henrik A. B.Zettergren, HenningHolm, Anne I. S.Schmidt, Henning T.Cederquist, Henrik
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