| Excited stilbene: intramolecular vibrational redistribution and solvation studied by femtosecond stimulated Raman spectroscopy. | |
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MedLine Citation:
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PMID: 20481560 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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Excited-state relaxation of cis- and trans-stilbene is traced with femtosecond stimulated Raman spectroscopy, exploiting S(n) <-- S(1) resonance conditions. For both isomers, decay in Raman intensity, shift of spectral positions, and broadening of the bands indicate intramolecular vibrational redistribution (IVR). In n-hexane this process effectively takes 0.5-0.7 ps. Analysis of the intensity decay allows us to further distinguish two phases for trans-stilbene: fast IVR within a subset of modes (approximately 0.3 ps) followed by slower equilibration over the full vibrational manifold (approximately 0.9 ps). In acetonitrile IVR completes with 0.15 ps; this acceleration may originate from symmetry breakage induced by the polar solvent. Another process, dynamic solvation by acetonitrile, is seen as spectral narrowing and characteristic band shifts of the C=C stretch and phenyl bending modes with 0.69 ps. Wavepacket motion is observed in both isomers as oscillation of low-frequency bands with their pertinent mode frequency (90 or 195 cm(-1) in trans-stilbene; 250 cm(-1) in cis-stilbene). Anharmonic coupling shows up as a modulation of high-frequency peak positions by phenyl/ethylene torsion modes of 57 and 90 cm(-1). Decay and shift of the 90 cm(-1) inverse Raman band within the first 0.3 ps suggests a gradual involvement of phenyl/ethylene torsion in relaxation. In cis- and trans-stilbene, low-frequency spectral changes are found within 0.15 ps, indicating an additional ultrafast process. |
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Authors:
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A Weigel; N P Ernsting |
Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: The journal of physical chemistry. B Volume: 114 ISSN: 1520-5207 ISO Abbreviation: J Phys Chem B Publication Date: 2010 Jun |
Date Detail:
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Created Date: 2010-08-16 Completed Date: 2010-12-02 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101157530 Medline TA: J Phys Chem B Country: United States |
Other Details:
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Languages: eng Pagination: 7879-93 Citation Subset: - |
Affiliation:
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Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany. weigelal@chemie.hu-berlin.de |
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