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Theoretical Studies on Vibrationally Resolved Optical Spectra of Polycyclic Aromatic Molecules
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. (Yi Luo's group)
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polycyclic aromatic molecules are of great interest owing to their many important applications in chemistry and have therefore been the focus of investigations for over half a century with spectroscopic techniques. This thesis is devoted to the modeling of vibrationally resolved optical spectra of polycyclic aromatic molecules. The general goal is to demonstrate the importance of nuclear motion on the electronic spectra and provide reliable spectral assignments and spectral fingerprints to distinguish different molecular isomers that are often not possible to be identified by experiments alone. In this thesis, four sets of polycyclic aromatic molecules have been systematically studied by using quantum chemistry methods. The simulated vibronic spectra are in good agreement with their experimental counterparts, which enables to provide correct reassignments for the electronic spectra.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2019. , p. 59
Series
TRITA-CBH-FOU ; 2019:4
Keywords [en]
Theoretical study, optical spectra, vibronic effect, polycyclic aromatic molecules
National Category
Theoretical Chemistry
Research subject
Theoretical Chemistry and Biology
Identifiers
URN: urn:nbn:se:kth:diva-241360ISBN: 978-91-7873-077-3 (print)OAI: oai:DiVA.org:kth-241360DiVA, id: diva2:1280405
Public defence
2019-02-22, FP41, Roslagstullsbacken 33, våningsplan 4,, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20190118

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-21Bibliographically approved
List of papers
1. The assignment of optical absorption spectra of protonated anthracene isomers:revisited
Open this publication in new window or tab >>The assignment of optical absorption spectra of protonated anthracene isomers:revisited
(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-241296 (URN)
Note

QC 20180118

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-18Bibliographically approved
2. A theoretical study on vibronic spectra and photo conversation process of protonated naphthalenes
Open this publication in new window or tab >>A theoretical study on vibronic spectra and photo conversation process of protonated naphthalenes
2018 (English)In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 205, p. 520-527Article in journal (Refereed) Published
Abstract [en]

The equilibrium structures and vibrational frequencies of the ground state and several singlet low-lying excited states of alpha-and beta-protonated naphthalenes (alpha-and beta-HN+) have been studied by time -dependent density -functional theory (TD-DFT). Within the Franck -Condon approximation, vibronic absorption spectra of alpha-HN+ and beta-HN+, together with the vibronic emission spectrum of alpha-HN+, have been calculated. The obtained good agreement between the theoretical and experimental spectra enables to correctly assign vibronic features in both absorption and emission spectra. Moreover, the non -radiative deactivation pathway from the low-lying excite states to the ground state in alpha-HN+ and beta-HN+, as well as the photo-induce proton transfer pathway, are investigated at the CASPT2/CASSCF/6-31G* level. Our study is helpful for understanding the photochemical behavior of these important polycyclic aromatic hydrocarbon molecules.

Place, publisher, year, edition, pages
Pergamon Press, 2018
Keywords
Vibronic spectra, Photo conversation, Theoretical study, Protonated naphthalenes
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-235992 (URN)10.1016/j.saa.2018.07.074 (DOI)000445713600061 ()30071500 (PubMedID)2-s2.0-85050638025 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20181015

Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2019-01-18Bibliographically approved
3. Theoretical studies on the vibrationally-resolved absorption and fluorescence spectra of H-Pyrene(+) and H-Coronene(+)
Open this publication in new window or tab >>Theoretical studies on the vibrationally-resolved absorption and fluorescence spectra of H-Pyrene(+) and H-Coronene(+)
2015 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 641, p. 57-61Article in journal (Refereed) Published
Abstract [en]

H-Pyrene and H-Coronene are important carrier candidates for the diffuse interstellar band. In order to understand the observed absorption and fluorescence emission spectra of H-Pyrene and H-Coronene, time-dependent density functional theory (TD-DFT) method and Franck-Condon approximation have been employed to simulate the corresponding vibrationally-resolved optical spectra. For H-Pyrene, the calculated absorption, emission and 0-0 band energies are in good agreement with the experimental values. The strong absorption and emission vibrational peaks near the 0-0 band match well with the experiment peaks. A noticeable deviation for several weak peaks far away from the origin band is observed, as a result of the vibronic coupling with other excited states. For H-Coronene, the predicted vibrationally resolved electronic absorption and emission spectra resemble very well their experimental counterparts spectra, allowing to fully assign the observed vibronic peaks.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:kth:diva-180132 (URN)10.1016/j.cplett.2015.10.034 (DOI)000365814700012 ()2-s2.0-84946727177 (Scopus ID)
Note

QC 20160114

Available from: 2016-01-14 Created: 2016-01-07 Last updated: 2019-01-18Bibliographically approved
4. A time-dependent density-functional theory and complete active space self-consistent field method study of vibronic absorption and emission spectra of coumarin
Open this publication in new window or tab >>A time-dependent density-functional theory and complete active space self-consistent field method study of vibronic absorption and emission spectra of coumarin
2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 1, p. 014306-Article in journal (Refereed) Published
Abstract [en]

Time-dependent density-functional theory (TD-DFT) and complete active space multiconfiguration self-consistent field (CASSCF) calculations have been used to determine equilibrium structures and vibrational frequencies of the ground state and several singlet low-lying excited states of coumarin. Vertical and adiabatic transition energies of S-1, S-2, and S-3 have been estimated by TD-B3LYP and CASSCF/PT2. Calculations predict that the dipole-allowed S-1 and S-3 states have a character of (1)(pi pi*), while the dipole-forbidden (1)(n pi*) state is responsible for S-2. The vibronic absorption and emission spectra of coumarin have been simulated by TD-B3LYP and CASSCF calculations within the Franck-Condon approximation, respectively. The simulated vibronic spectra show good agreement with the experimental observations available, which allow us to reasonably interpret vibronic features in the S-0 -> S-1 and S-0 -> S-3 absorption and the S-0 <- S-1 emission spectra. Based on the calculated results, activity, intensity, and density of the vibronic transitions and their contribution to the experimental spectrum profile have been discussed.

Keywords
Multireference Perturbation-Theory, Excited-States, Fluorescence, Derivatives
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-149509 (URN)10.1063/1.4885845 (DOI)000339622000018 ()2-s2.0-84904012420 (Scopus ID)
Note

QC 20140822

Available from: 2014-08-22 Created: 2014-08-22 Last updated: 2019-01-18Bibliographically approved

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