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A. Lau - One of the best experts on this subject based on the ideXlab platform.
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Evidence of strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by picosecond CARS spectroscopy
Chemical Physics Letters, 1999Co-Authors: S. Hogiu, Wolfgang Werncke, M. Pfeiffer, A. LauAbstract:Abstract Applying the polarization-sensitive variant of coherent anti-Stokes raman scattering (CARS) with picosecond time resolution solvent-dependent vibrational shifts and depolarization ratios of vibrational resonances of the first Excited Singlet State of diphenylhexatriene were investigated. The depolarization ratios of all observed Raman lines ( ρ R ∼0.72) near the transient absorption of the Excited State show the dominance of anisotropic scattering originating from vibrations of the same symmetry species. Vibrational frequencies were determined under polarization conditions avoiding spectral interference with the electronic background. Frequencies of the two broad CC stretching bands in the spectral range above 1600 cm −1 increase with decreasing polarizability of the solvent indicating strong vibronic coupling in the first Excited Singlet State.
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Strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by an asymmetric low-frequency mode
Chemical Physics Letters, 1998Co-Authors: M. Pfeiffer, S. Hogiu, Wolfgang Werncke, A. Kummrow, A. LauAbstract:Abstract Raman studies of diphenylhexatriene in the first Excited Singlet State evidence strong vibronic coupling between two close 1Bu/2Ag States. The geometrical change after photoexcitation contains a dominant contribution of a low-frequency mode with bu symmetry near 40 cm−1. This mode is identified as a relatively strong line in the Raman spectrum. Vibronic coupling mainly affects two CC stretching Raman bands near 1700 cm−1. A two-dimensional effective potential for the lowest Excited Singlet State is derived which models the coupling between the coordinate of the 40 cm−1 mode and the CC stretching coordinate, thereby explaining the occurrence of the two bands and their strong solvent shift. The model gives, in the zero gap limit, a double-well potential for the CC stretching coordinate, due to the pseudo-Jahn–Teller effect. Modulation of this potential by the low-frequency cycle explains the spectral broadening observed in the Raman spectra.
S. Hogiu - One of the best experts on this subject based on the ideXlab platform.
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Evidence of strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by picosecond CARS spectroscopy
Chemical Physics Letters, 1999Co-Authors: S. Hogiu, Wolfgang Werncke, M. Pfeiffer, A. LauAbstract:Abstract Applying the polarization-sensitive variant of coherent anti-Stokes raman scattering (CARS) with picosecond time resolution solvent-dependent vibrational shifts and depolarization ratios of vibrational resonances of the first Excited Singlet State of diphenylhexatriene were investigated. The depolarization ratios of all observed Raman lines ( ρ R ∼0.72) near the transient absorption of the Excited State show the dominance of anisotropic scattering originating from vibrations of the same symmetry species. Vibrational frequencies were determined under polarization conditions avoiding spectral interference with the electronic background. Frequencies of the two broad CC stretching bands in the spectral range above 1600 cm −1 increase with decreasing polarizability of the solvent indicating strong vibronic coupling in the first Excited Singlet State.
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Strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by an asymmetric low-frequency mode
Chemical Physics Letters, 1998Co-Authors: M. Pfeiffer, S. Hogiu, Wolfgang Werncke, A. Kummrow, A. LauAbstract:Abstract Raman studies of diphenylhexatriene in the first Excited Singlet State evidence strong vibronic coupling between two close 1Bu/2Ag States. The geometrical change after photoexcitation contains a dominant contribution of a low-frequency mode with bu symmetry near 40 cm−1. This mode is identified as a relatively strong line in the Raman spectrum. Vibronic coupling mainly affects two CC stretching Raman bands near 1700 cm−1. A two-dimensional effective potential for the lowest Excited Singlet State is derived which models the coupling between the coordinate of the 40 cm−1 mode and the CC stretching coordinate, thereby explaining the occurrence of the two bands and their strong solvent shift. The model gives, in the zero gap limit, a double-well potential for the CC stretching coordinate, due to the pseudo-Jahn–Teller effect. Modulation of this potential by the low-frequency cycle explains the spectral broadening observed in the Raman spectra.
Bern Kohler - One of the best experts on this subject based on the ideXlab platform.
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strickler berg analysis of Excited Singlet State dynamics in dna and rna nucleosides
Faraday Discussions, 2004Co-Authors: Boiko Cohen, Carlos E Crespohernandez, Bern KohlerAbstract:The Excited Singlet State lifetime of the ribonucleoside uridine was found to be 210 ± 30 fs by femtosecond transient absorption spectroscopy. This value is considerably shorter than all previous time-domain measurements. This result and our previous lifetime measurements [see J.-M. L. Pecourt, J. Peon and B. Kohler, J. Am. Chem. Soc., 2001, 123, 10 370] for the other common nucleosides are compared with lifetimes calculated from available photophysical data using the Strickler–Berg (SB) equation. The calculated lifetimes for pyrimidine nucleosides are 10–25% lower than the lifetimes measured in femtosecond transient absorption experiments. For the purine nucleosides, guanosine and adenosine, consideration of just the lowest 1π → π* transition led to predicted lifetimes that are three times greater than experimental ones. On the other hand, inclusion of both of the lowest energy 1π → π* absorption bands in the SB equation resulted in much better agreement with the experimental values. This suggests that both 1ππ* States of the purine nucleosides contribute to their emission. Decay by the bright 1ππ* State (or States, in the case of the purines) is believed to be responsible for the experimentally observed lifetimes.
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Strickler–Berg analysis of Excited Singlet State dynamics in DNA and RNA nucleosides
Faraday discussions, 2004Co-Authors: Boiko Cohen, Carlos E. Crespo-hernández, Bern KohlerAbstract:The Excited Singlet State lifetime of the ribonucleoside uridine was found to be 210+/-30 fs by femtosecond transient absorption spectroscopy. This value is considerably shorter than all previous time-domain measurements. This result and our previous lifetime measurements [see J.-M. L. Pecourt, J. Peon and B. Kohler, J. Am. Chem. Soc., 2001, 123, 10 370] for the other common nucleosides are compared with lifetimes calculated from available photophysical data using the Strickler-Berg (SB) equation. The calculated lifetimes for pyrimidine nucleosides are 10-25% lower than the lifetimes measured in femtosecond transient absorption experiments. For the purine nucleosides, guanosine and adenosine, consideration of just the lowest 1pi --> pi* transition led to predicted lifetimes that are three times greater than experimental ones. On the other hand, inclusion of both of the lowest energy 1pi --> pi* absorption bands in the SB equation resulted in much better agreement with the experimental values. This suggests that both 1pi pi* States of the purine nucleosides contribute to their emission. Decay by the bright 1pi pi* State (or States, in the case of the purines) is believed to be responsible for the experimentally observed lifetimes.
M. Pfeiffer - One of the best experts on this subject based on the ideXlab platform.
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Evidence of strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by picosecond CARS spectroscopy
Chemical Physics Letters, 1999Co-Authors: S. Hogiu, Wolfgang Werncke, M. Pfeiffer, A. LauAbstract:Abstract Applying the polarization-sensitive variant of coherent anti-Stokes raman scattering (CARS) with picosecond time resolution solvent-dependent vibrational shifts and depolarization ratios of vibrational resonances of the first Excited Singlet State of diphenylhexatriene were investigated. The depolarization ratios of all observed Raman lines ( ρ R ∼0.72) near the transient absorption of the Excited State show the dominance of anisotropic scattering originating from vibrations of the same symmetry species. Vibrational frequencies were determined under polarization conditions avoiding spectral interference with the electronic background. Frequencies of the two broad CC stretching bands in the spectral range above 1600 cm −1 increase with decreasing polarizability of the solvent indicating strong vibronic coupling in the first Excited Singlet State.
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Strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by an asymmetric low-frequency mode
Chemical Physics Letters, 1998Co-Authors: M. Pfeiffer, S. Hogiu, Wolfgang Werncke, A. Kummrow, A. LauAbstract:Abstract Raman studies of diphenylhexatriene in the first Excited Singlet State evidence strong vibronic coupling between two close 1Bu/2Ag States. The geometrical change after photoexcitation contains a dominant contribution of a low-frequency mode with bu symmetry near 40 cm−1. This mode is identified as a relatively strong line in the Raman spectrum. Vibronic coupling mainly affects two CC stretching Raman bands near 1700 cm−1. A two-dimensional effective potential for the lowest Excited Singlet State is derived which models the coupling between the coordinate of the 40 cm−1 mode and the CC stretching coordinate, thereby explaining the occurrence of the two bands and their strong solvent shift. The model gives, in the zero gap limit, a double-well potential for the CC stretching coordinate, due to the pseudo-Jahn–Teller effect. Modulation of this potential by the low-frequency cycle explains the spectral broadening observed in the Raman spectra.
Wolfgang Werncke - One of the best experts on this subject based on the ideXlab platform.
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Evidence of strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by picosecond CARS spectroscopy
Chemical Physics Letters, 1999Co-Authors: S. Hogiu, Wolfgang Werncke, M. Pfeiffer, A. LauAbstract:Abstract Applying the polarization-sensitive variant of coherent anti-Stokes raman scattering (CARS) with picosecond time resolution solvent-dependent vibrational shifts and depolarization ratios of vibrational resonances of the first Excited Singlet State of diphenylhexatriene were investigated. The depolarization ratios of all observed Raman lines ( ρ R ∼0.72) near the transient absorption of the Excited State show the dominance of anisotropic scattering originating from vibrations of the same symmetry species. Vibrational frequencies were determined under polarization conditions avoiding spectral interference with the electronic background. Frequencies of the two broad CC stretching bands in the spectral range above 1600 cm −1 increase with decreasing polarizability of the solvent indicating strong vibronic coupling in the first Excited Singlet State.
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Strong vibronic coupling in the first Excited Singlet State of diphenylhexatriene by an asymmetric low-frequency mode
Chemical Physics Letters, 1998Co-Authors: M. Pfeiffer, S. Hogiu, Wolfgang Werncke, A. Kummrow, A. LauAbstract:Abstract Raman studies of diphenylhexatriene in the first Excited Singlet State evidence strong vibronic coupling between two close 1Bu/2Ag States. The geometrical change after photoexcitation contains a dominant contribution of a low-frequency mode with bu symmetry near 40 cm−1. This mode is identified as a relatively strong line in the Raman spectrum. Vibronic coupling mainly affects two CC stretching Raman bands near 1700 cm−1. A two-dimensional effective potential for the lowest Excited Singlet State is derived which models the coupling between the coordinate of the 40 cm−1 mode and the CC stretching coordinate, thereby explaining the occurrence of the two bands and their strong solvent shift. The model gives, in the zero gap limit, a double-well potential for the CC stretching coordinate, due to the pseudo-Jahn–Teller effect. Modulation of this potential by the low-frequency cycle explains the spectral broadening observed in the Raman spectra.