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A computational study of radiationless deactivation mechanisms of furan
Stockholm University, Faculty of Science, Department of Physics. (Chemical Physics)
Stockholm University, Faculty of Science, Department of Physics. (Chemical Physics)
2011 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 379, no 1-3, 6-12 p.Article in journal (Refereed) Published
Abstract [en]

Possible mechanisms for the radiationless deactivation of photo-excited furan have been investigated using high-level electronic structure methods. Two different conical intersections between the S0 and S1 electronic states have been characterized, both involving various degrees of CO bond cleavage. One of these corresponds to a planar ring-opened structure and the other to an asymmetric ring-puckered structure. Calculations have been performed in order to establish the vertical electronic spectrum and to investigate the behaviour of the potential energy surfaces as the intersections are approached. The present results indicate that both crossings can be accessed through exothermic and barrierless processes after vertical excitation into the optically bright S2(ππ∗) state. These features make them good candidates to account for efficient radiationless deactivation in furan. The deactivation pathways considered in the present work are close analogues of those previously described for other five-membered heterocycles.

Place, publisher, year, edition, pages
2011. Vol. 379, no 1-3, 6-12 p.
National Category
Theoretical Chemistry Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-67333DOI: 10.1016/j.chemphys.2010.10.002ISI: 000286658800002OAI: oai:DiVA.org:su-67333DiVA: diva2:470313
Available from: 2011-12-28 Created: 2011-12-28 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Photo-induced molecular processes and charge recombination reactions driven by non-adiabatic couplings
Open this publication in new window or tab >>Photo-induced molecular processes and charge recombination reactions driven by non-adiabatic couplings
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on a number of theoretical studies of molecular processes in which non-adiabatic effects play a crucial role. The main part is devoted to the photophysics and photochemistry of five-membered aromatic heterocyclic compounds, with particular focus on furan and thiophene. These species absorb light in the UV region of the spectrum, but exhibits neither fluorescence nor phosphorescence. A plausible explanation for this is the presence of very fast radiationless deactivation mechanisms that depopulate the excited states before emission can occur. In the present thesis, several possible such mechanisms are considered based on the results of static electronic structure calculations as well as mixed quantum-classical dynamics simulations. A common feature of the investigated pathways is the presence of easily accessible conical intersections (surface crossings) through which non-adiabatic population transfer to the electronic ground state may take place. Also considered in the present work are the bond-breaking/bond-forming processes that are expected to follow once the ground state has been reached.

Another prominent example of non-adiabatic processes is charge recombination reactions involving either two oppositely charged ions or a cation and an electron. Here, the reactants and products belong to different electronic states of the system as a whole and therefore a non-adiabatic transition is necessary for the recombination to occur. Two such processes are considered in the present thesis; mutual neutralization of oppositely charged hydrogen ions and dissociative recombination of the formyl and iso-formyl cations. The cross sections (rate coefficients) and underlying mechanisms of these reactions are investigated at a fully quantum mechanical level.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 67 p.
Keyword
Non-adiabatic processes, Photophysics, Photochemistry, Radiationless deactivation, Conical intersections, Five-membered aromatic heterocyclic compounds, Mutual neutralization, Dissociative recombination
National Category
Theoretical Chemistry Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-72456 (URN)978-91-7447-458-9 (ISBN)
Public defence
2012-03-09, lecture room FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Manuscript. Paper 5. Submitted. Available from: 2012-02-16 Created: 2012-02-12 Last updated: 2012-02-13Bibliographically approved

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