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  • 1
    Electronic Resource
    Electronic Resource
    Femtosecond probing of exciton relaxation and transport dynamics in polybithiophene (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 1185-1190 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relaxation and transport dynamics of singlet excitons in 100 nm thick, electrochemically prepared polybithiophene films were investigated by monitoring the time evolution of photoinduced bleaching of the S0–S1 absorption and photoinduced absorption (S1–Sn) with femtosecond resolved transient absorption spectroscopy. The decay dynamics of both photoinduced bleaching and photoinduced absorption in the spectral range from 500 to 800 nm are observed to be independent of the pump pulse wavelength and can be fitted by a double exponential, the time constants of which are τ1=120±20 fs and τ2=2±0.3 ps. The fast decay process with ∼τ1=120 fs was ascribed to the transport dynamics of the initially generated free excitons migrating over parallel aligned polymer segments to structural defects acting as traps. The competing process, occurring predominantly in structurally disordered regions, is structural relaxation of the initially generated free excitons to self-trapped excitons decaying with a lifetime of about 2 ps. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479303
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  • 2
    Electronic Resource
    Electronic Resource
    Transport Phenomena of Singlet Excitations in the Guest Band of Doped Molecular Crystals (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 7958-7962 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100084a007
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  • 3
    Electronic Resource
    Electronic Resource
    Pseudolocal phonons in p-terphenyl: pentacene single crystals (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1742-1749 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structural nature of the phonon sidebands in the fluorescence and excitation spectra of pentacene guests in p-terphenyl crystals at 4.2 K are investigated using site-selective spectroscopy. The distinct features in the phonon sideband structure were observed to depend significantly on the guest site configuration of pentacene occupying four inequivalent sites in the triclinic p-terphenyl lattice. The sharp peaks dominating the phonon sideband structure are assumed to arise from the pseudolocal phonons. The eigenvalues and eigenvectors of the pseudolocal phonons are calculated carrying out a modified normal mode analysis on the distinct pentacene site configurations including the contribution of all intermolecular atom-pair interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463161
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  • 4
    Electronic Resource
    Electronic Resource
    Phonon-induced site relaxation of tetracene guests in p-terphenyl single crystals (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7197-7202 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Site relaxation processes of tetracene-h12 and tetracene-d12 guests in p-terphenyl crystals are examined using high-resolution fluorescence and fluorescence excitation spectroscopy. Two of the four sites, the so-called O3 and O4 sites, undergo this process and their phonon sidebands observed in the excitation spectra are characterized by an exceptionally long and well resolved progression of a low-frequency (pseudo-) local phonon mode superimposed on a broad background. Perdeuteration of tetracene results in a frequency reduction of the progression forming mode which identifies this local phonon as a guest librational mode. The latter is suggested to induce the site relaxation via guest reorientation processes. The intensity distribution in the phonon sideband of the O3 site indicates a reorientational angle of ∼21° about the L-axis for the tetracene guest in the excited singlet state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463544
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  • 5
    Electronic Resource
    Electronic Resource
    Theory and calculation of singlet excitation energy transfer in mixed molecular crystals (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 9183-9190 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of excitation energy transport among dipole–dipole interacting guests in mixed molecular crystals is carried out. To describe the temporal evolution of the excited state population, we derive a microscopic theory which treats an ensemble of dipole–dipole interacting guest molecules homogeneously distributed among two inequivalent sites of a host lattice. The theory is based on a generalized effective Hamiltonian accounting for intramolecular excited state depopulation and excitation energy transfer. The results are applied to the analysis of experimental data obtained from transient grating experiments in p-terphenyl:pentacene mixed molecular crystals. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468867
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  • 6
    Electronic Resource
    Electronic Resource
    Optical properties of perturbed NO 2 − ions in KNO2 doped NaNO2 single crystals (1990)
    Springer
    Theoretical chemistry accounts 77 (1990), S. 395-407 
    Details
    ISSN: 1432-2234
    Keywords: NO 2 − ions ; KNO2 doped NaNO2 single crystals ; Time-resolved fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On the basis of high-resolution and time-resolved fluorescence spectra, a model is proposed for the interpretation of the fluorescence lines originating from various perturbed NO 2 − centers situated in the neighbourhood of the K+ ion of the NaNO2:KNO2 crystal. Since their excited state energies are lower than that of the host, these perturbed NO 2 − ions act as traps for the host singlet exciton. On the assumption that the perturbation giving rise to those traps results from an interaction of the impurity ion K+ with its nearest neighbours, the observed position of the energy levels of the various traps can be reconciled with crystal field calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01374530
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  • 7
    Electronic Resource
    Electronic Resource
    Coupling of Chromophores: Carotenoids and Photoactive Diarylethenes - Photoreactivity versus Radiationless Deactivation (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2333-2338 
    Details
    ISSN: 1434-193X
    Keywords: Photochromism ; Optical switches ; Dithienylethenes ; Carotenoids ; Valence isomerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New photochromic carotenoid-like chromophores containing the dithienylperfluorocyclopentene fragment have been synthesized and characterized by UV/Vis spectroscopy. The quantum yields of the photochromic forward and back reactions of these compounds have been determined and are found to decrease sharply with increasing chain length of the substituent. This decrease in quantum yield can be rationalized in terms of a decrease of the excitation density at the central photoreactive unit and of the excited state lifetime, which is known to shorten in carotenoids with increasing chain length.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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