Disentanglement of triplet and singlet states of azobenzene: direct EELS detection and QMC modeling

Singlet and triplet excited states of trans -azobenzene have been measured in the gas phase by electron energy loss spectroscopy (EELS). In order to interpret the strongly overlapping singlet and triplet bands in the spectra a set of large-scale correlated quantum Monte-Carlo (QMC) simulations was p...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2011-01, Vol.13 (47), p.2939-2945
Main Authors: Dubecký, M, Derian, R, Horváthová, L, Allan, M, Štich, I
Format: Article
Language:English
Subjects:
Band spectra
Banded structure
Bands
Chemistry
Computer simulation
Electron energy loss spectroscopy
Exact sciences and technology
Excitation spectra
General and physical chemistry
Mathematical analysis
Spectra
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Summary:Singlet and triplet excited states of trans -azobenzene have been measured in the gas phase by electron energy loss spectroscopy (EELS). In order to interpret the strongly overlapping singlet and triplet bands in the spectra a set of large-scale correlated quantum Monte-Carlo (QMC) simulations was performed. The EELS/QMC combination of methods yields an excellent agreement between theory and experiment and for the two low-lying excited singlet and two low-lying triplet states permitted their unambiguous assignment. In addition, EELS revealed two overlapping electronic states in the band commonly assigned as S 2 , the lower one with a pronounced vibrational structure, the upper one structureless. Finally, the agreement between theory and experiment was shown to further increase by taking computationally into account the finite temperature effects. Name that state! Electronic structure, including singlet and triplet states, of the iconic photoswitchable azobenzene molecule revealed by electron energy loss spectra and correlated quantum Monte-Carlo simulations.
ISSN:1463-9076
1463-9084
DOI:10.1039/c1cp22520k