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Polycyclic aromatic hydrocarbon-isomer fragmentation pathways: Case study for pyrene and fluoranthene molecules and clusters
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, no 6, 064302- p.Article in journal (Refereed) Published
Abstract [en]

We report on measurements of the ionization and fragmentation of polycyclic aromatic hydrocarbon (PAH) targets in Xe(20+) + C(16)H(10) and Xe(20+) + [C(16)H(10)](k) collisions and compare results for the two C(16)H(10) isomers: pyrene and fluoranthene. For both types of targets, i.e., for single PAH molecules isolated in vacuum or for isomerically pure clusters of one of the molecules, the resulting fragment spectra are surprisingly similar. However, we do observe weak but significant isomer effects. Although these are manifested in very different ways for the monomer and cluster targets, they both have at their roots small differences (<2.5 eV) between the total binding energies of neutral, and singly and multiply charged pyrene and fluoranthene monomers. The results will be discussed in view of the density functional theory calculations of ionization and dissociation energies for fluoranthene and pyrene. A simple classical over-the-barrier model is used to estimate cross sections for single-and multiple-electron transfer between PAHs and ions. Calculated single and multiple ionization energies, and the corresponding model PAH ionization cross sections, are given.

Place, publisher, year, edition, pages
2011. Vol. 135, no 6, 064302- p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-68323DOI: 10.1063/1.3622589ISI: 000293955000012OAI: oai:DiVA.org:su-68323DiVA: diva2:477380
Note

authorCount :17

Available from: 2012-01-13 Created: 2012-01-03 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Ions colliding with Polycyclic Aromatic Hydrocarbons and Fullerenes
Open this publication in new window or tab >>Ions colliding with Polycyclic Aromatic Hydrocarbons and Fullerenes
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis a series of experiments on collisions between atomic projectile ions at keV energies and target vapors of either isolated molecules or van der Waals clusters is presented and analyzed. The atomic ions are produced in an Electron Cyclotron Resonance (ECR) ion source, accelerated and guided into the target volume. The charged target collision products are mass-to-charge analyzed in a time-of-flight spectrometer. The Polycyclic Aromatic Hyrdrocarbons (PAHs) Anthracene (C14H10), Coronene (C24H12), two C16H10 isomers, Pyrene and Fluoranthene, and the fullerene C60 are examined.

For projectile ions in low charge states, small impact parameter collisions dominate, which leads to internal heating of the target. With isolated molecules as targets, this typically results in ionization and often also in fragmentation. For cluster targets energy and charge are rapidly distributed among the cluster building blocks. This is followed by cluster evaporation and very limited fragmentation of the individual molecules. C119+ and C118+ are observed as products. These are due to the formation of the reactive C58/59+ ions by direct knockout processes, which react with another C60 of the cluster to form dumb-bell shaped molecules.

For projectile ions of high charge (Xe20+) larger impact parameters dominate, leading to little internal heating. For isolated molecule targets, intact molecular ions are the main collision products. Charged fragments stem mostly from multifragmentation following ionization to high charge states. For cluster targets, the collision products consist mainly of singly charged monomers. Fragmentation of the individual molecules is comparatively strong. This suggests a quick distribution of charges followed by a Coulomb explosion, which leads to internal heating.

The results show that weakly bound clusters do not sustain the impact of keV-ions and that it is possible to form new molecular structures.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2013. 118 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-88427 (URN)978-91-7447-649-1 (ISBN)
Public defence
2013-04-30, lecture hall FD5, AlbaNova universitetscentrum, Roslagstullbacken 21, Stockholm, 10:15 (English)
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Supervisors
Note

At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Submitted.

Available from: 2013-04-08 Created: 2013-03-14 Last updated: 2014-03-28Bibliographically approved

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Seitz, FabianHolm, Anne I. S.Zettergren, HenningJohansson, Henrik A. B.Rosén, StefanSchmidt, Henning T.Cederquist, Henrik
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