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Experimental and theoretical study of the photodissociation of bromo-3-fluorobenzene
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
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2008 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 3, 034307- p.Article in journal (Refereed) Published
Abstract [en]

The UV photodissociation of bromo-3-fluorobenzene under collisionless conditions has been studied as a function of the excitation wavelength between 255 and 265 nm. The experiments were performed using ultrafast pump-probe laser spectroscopy. To aid in the interpretation of the results, it was necessary to extend the theoretical framework substantially compared to previous studies, to also include quantum dynamical simulations employing a two-dimensional nuclear Hamiltonian. The nonadiabatic potential energy surfaces (PES) were parameterized against high-level MS-CASTP2 quantum chemical calculations, using both the C–Br distance and the out-of-plane bending of the bromine as nuclear parameters. We show that the wavelength dependence of the photodissociation via the S01ππ*1πσ* channel, accessible with a ∼ 260 nm pulse, is captured in this model. We thereby present the first correlation between experiments and theory within the quantitative regime.

Place, publisher, year, edition, pages
2008. Vol. 128, no 3, 034307- p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96760DOI: 10.1063/1.2819093ISI: 000252471100017OAI: oai:DiVA.org:uu-96760DiVA: diva2:171441
Available from: 2008-02-26 Created: 2008-02-26 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Photochemistry of Phenyl Halides
Open this publication in new window or tab >>Photochemistry of Phenyl Halides
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We have studied fundamental aspects of photo-induced dissociation kinetics and dynamics in several phenyl halides. By combining femtosecond pump-probe measurements with ab initio calculations we are able to account for several observations. In mixed phenyl halides, the dissociation kinetics is found to be dependent on the nature, the number, and the position of the substituents, and also on the excitation wavelength. A surprisingly large reduction in the dissociation time constant, compared to that of bromobenzene (~30 ps), is observed when having two or more fluorine atoms. For example, in bromopentafluorobenzene a subpicosecond time constant is obtained. This can be explained by a significant lowering of the repulsive potential energy curves (PEC) along the C-Br bond. However, several of the experimental results cannot be accounted for by one-dimensional PECs. Therefore, we suggest a refined model for the dissociation, in which the excited states of the same spin multiplicity are coupled by employing multidimensional potential energy surfaces. This model has been explicitly evaluated by quantum dynamics simulations in the case of 3-BrFPh, and it seems to be capable of capturing the main features in the measured kinetics. Thereby we are also able to clarify the role of spin-orbit coupling in these molecules.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 417
Keyword
Chemistry, Photochemistry, Predissociation, Phenyl halides, Excited states, Substituent effects, Pump-probe spectroscopy, Molecular beam, Dynamics, Kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-8602 (URN)978-91-554-7146-0 (ISBN)
Public defence
2008-04-24, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2011-03-14Bibliographically approved
2. Theoretical Photochemistry: Halogenated Arenes, Phytochromobilin, Ru(II)polypyridyl complexes and 6-4 photoadducts
Open this publication in new window or tab >>Theoretical Photochemistry: Halogenated Arenes, Phytochromobilin, Ru(II)polypyridyl complexes and 6-4 photoadducts
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents Quantum Chemical calculations on the Photochemistry of Halogenated benzenes, Phytochromobilin, Ruthenium Polypyridyl complexes and 6-4 photoadducts in DNA. The work is focused on improving the understanding of a number of experimentally observed photochemical processes in these systems. New results regarding the mechanism of photodissociation of halogenated arenes, photointerconversion of phytochromobilin are presented, as well as of the photoprocesses of Ruthenium Polypyridyl complexes and new mechanistic insights in the repair of 6-4 photoadducts in DNA.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 394
Keyword
Quantum chemistry, Quantum Chemistry, Halogenated Arenes, Phytochromobilin, Phytochrome, Ruthenium, 6-4 photoadducts, Photochemistry, Kvantkemi
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-8469 (URN)978-91-554-7096-8 (ISBN)
Public defence
2008-03-19, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2008-02-26 Created: 2008-02-26 Last updated: 2011-03-14Bibliographically approved

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Karlsson, Hans O.

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