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  • 1
    Digitale Medien
    Digitale Medien
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 97-98 (Apr. 2004), p. 201-206 
    ISSN: 1662-9779
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Physik
    Notizen: The linear and nonlinear optical properties of pure 3,3'-bis(3-carboxypropyl)-5,5',6,6'- tetrachloro-1,1'-dioctylbenzimidacarbocyanine (C〈sub〉8〈/sub〉O〈sub〉3〈/sub〉) aggregates as well as of C〈sub〉8〈/sub〉O〈sub〉3〈/sub〉 aggregates in the presence of PVA are studied at room temperature. The obtained results reveal that absorption spectra of both aggregates are governed by four absorption bands. Three of these represent transitions having dipole moments oriented parallel to the axis of the aggregate and one oriented perpendicular to it. The two lower energy parallel transitions are found to be weakly coupled which suggests that they represent two excitons located on different walls of the double-wall cylinder. In contrast, the lowest energy parallel transition and the transition having a transition dipole moment oriented perpendicular to the aggregate axis share the same ground state which reveals that they belong to the same exciton band. The manner of modification of the linear absorption with addition of PVA as well as the similarity of the pump-probe spectra of the two investigated aggregates suggests that this exciton band originates from the inner wall of the double-wall cylinder
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3571-3576 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: This work is concerned with the theory of concentration self-quenching of luminescence due to incoherent energy transfer between randomly distributed molecules. A simple model of self-quenching is considered, in which luminescent molecules within a critical distance of each other act as perfect traps. Due to the statistical nature of these traps, few practical results can be obtained from systematic or formal theories. We demonstrate, however, that within the framework of hopping theories for energy transfer an exact and a simple intuitive treatment of the donor and trap distributions differ only very little in their results for the quantum yield and emission anisotropy.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3577-3582 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present high accuracy Monte Carlo simulations on the steady state fluorescence quantum yield and anisotropy for systems in which concentration self-quenching due to incoherent energy transfer between randomly distributed molecules occurs. A simple model of self-quenching is considered, in which luminescent molecules within a critical distance of each other act as perfect traps. The simulations are based on the complete solution of the coupled rate equations for a randomly chosen distribution of molecules in a finite box. Finite size effects are systematically investigated. The results are used to assess the validity of simple analytic theories, such as Burshtein's theory of hopping transfer, which is found to give a good semiquantitative description of the fluorescence quantities. Furthermore, we show that truncating the transfer rate in such a way that, on the average, 10–20 molecules are within reach of an excitation residing on a given molecule, induces large deviations in the yield. We point out that this is a serious source of error in previous simulations.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4438-4441 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The incorporation is studied of the orientation factor occurring in the complete Förster rate of incoherent energy transfer, into the theory of concentration self-quenching by statistical pairs of luminescent molecules. Within Burshtein's theory of hopping transport, exact results for the steady state donor fluorescence yield and emission anisotropy are obtained for three-dimensional systems. Two opposite limits to treat the orientations of the molecular transition dipoles within statistical pairs are considered, and it appears that in both cases the fluorescence yield is substantially influenced by inclusion of the orientation factor into the transfer kinetics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Chemical Physics Letters 222 (1994), S. 450-456 
    ISSN: 0009-2614
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Chemical Physics Letters 203 (1993), S. 371-377 
    ISSN: 0009-2614
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Chemical Physics Letters 171 (1990), S. 529-536 
    ISSN: 0009-2614
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2990-2997 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A theory is presented that incorporates the effect of orientational correlations between luminescent molecules on the fluorescence depolarization due to incoherent energy transfer. The luminescent molecules are embedded in a homogeneous two- or three-dimensional medium which is in an axially symmetric phase with the xy plane as a symmetry plane, and consists of axially symmetric molecules. For the general orientational singlet distribution and the general form of orientational correlations consistent with these symmetries, we derive analytical expressions for the anisotropy of fluorescence emission. In a no back transfer model, numerical results are evaluated for a simple choice of correlations that tend to align nearby molecules. In a pure donor system, the anisotropy of fluorescence is found to be strongly dependent on these correlations. By ignoring them, the critical transfer distance, as obtained from depolarization experiments, may be drastically underestimated. In a system where donors are surrounded by a huge majority of traps, the critical transfer distance can be determined from the intensity of trap fluorescence. Its anisotropy also strongly depends on correlations and may thus give an indication of the correlation length scale.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Luminescence 53 (1992), S. 101-104 
    ISSN: 0022-2313
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Nuclear Instruments and Methods In Physics Research 215 (1983), S. 225-230 
    ISSN: 0167-5087
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Physik
    Materialart: Digitale Medien
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