University of Oulu

Pihlava, L., Niskanen, J., Kooser, K., Stråhlman, C., Maclot, S., Kivimäki, A., & Kukk, E. (2021). Photodissociation dynamics of halogenated aromatic molecules: The case of core-ionized tetrabromothiophene. Physical Chemistry Chemical Physics, 23(37), 21249–21261.

Photodissociation dynamics of halogenated aromatic molecules : the case of core-ionized tetrabromothiophene

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Author: Pihlava, Lassi1; Niskanen, Johannes1; Kooser, Kuno1,2;
Organizations: 1Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
2Institute of Physics, University of Tartu, W. Ostwaldi 1, EE-50411 Tartu, Estonia
3Department of Materials Science and Applied Mathematics, Malmö University, SE-20506 Malmö, Sweden
4Department of Physics, Gothenburg University, Box 100, SE-40530 Gothenburg, Sweden
5MAX IV Laboratory, Lund University, SE-22100 Lund, Sweden
6Nano and Molecular Systems Research Unit, University of Oulu, FI-90570 Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.5 MB)
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Language: English
Published: Royal Society of Chemistry, 2021
Publish Date: 2023-01-11


We studied the gas-phase photodissociation of a fully halogenated aromatic molecule, tetrabromothiophene, upon core–shell ionization by using synchrotron radiation and energy-resolved multiparticle coincidence spectroscopy. Photodynamics was initiated by the selective soft X-ray ionization of three elements — C, S, and Br — leading to the formation of dicationic states by Auger decay. From a detailed study of photodissociation upon Br 3d ionization, we formulate a general fragmentation scheme, where dissociation into neutral fragments and a pair of cations prevails, but dicationic species are also produced. We conclude that dicationic tetrabromothiophene typically undergoes deferred charge separation (with one of the ions being often Br⁺) that may be followed by secondary dissociation steps, depending on the available internal energy of the parent dication. Observations suggest that the ejection of neutral bromine atoms as the first step of deferred charge separation is a prevailing feature in dicationic dissociation, although sometimes in this step the C—Br bonds appear to remain intact and the thiophene ring is broken instead. Ionization-site-specific effects are observed particularly in doubly charged fragments and as large differences in the yields of the intact parent dication. We interpret these effects, using first-principles calculations and molecular dynamics simulations of core-hole states, as likely caused by the geometry changes during the core-hole lifetime.

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Series: PCCP. Physical chemistry chemical physics
ISSN: 1463-9076
ISSN-E: 1463-9084
ISSN-L: 1463-9076
Volume: 23
Issue: 37
Pages: 21249 - 21261
DOI: 10.1039/d1cp03097c
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Funding: LP acknowledges financial support from The Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. JN acknowledges the Academy of Finland for funding via project 331234. SM acknowledges financial support from the Knut and Alice Wallenberg Foundation and the COST Action CA18212 – Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology). EK acknowledges funding by the Academy of Finland via project 295551. We acknowledge the MAX IV Laboratory for time on Beamline FinEstBeAMS under proposal 20190446. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research Council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496.
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