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  • 1
    Electronic Resource
    Electronic Resource
    Optical absorption and fluorescence spectroscopy of stable diacetylene oligomer molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 95-99 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The first fluorescence emission spectra of polydiacetylene oligomer molecules are presented. The spectral features of the low temperature absorption and emission spectra of monomer, dimer, trimer, tetramer, and polymer molecules are discussed. The preparation of the stable oligomer molecules via the reactive intermediates of the solid state polymerization is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454490
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  • 2
    Electronic Resource
    Electronic Resource
    Reaction kinetics of the solid state polymerization in diacetylene crystals (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5541-5553 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report on experimental and theoretical studies concerning the reaction kinetics of the solid state polymerization in diacetylene crystals. The individual reaction steps of the short-chain reaction intermediates (dimer, trimer, tetramer, ...) have been investigated by time resolved ESR and optical spectroscopy. In a microscopic theory energy barriers of molecular translations and rotations as well as the mismatch of the oligomer molecules in the crystal matrix are taken into account. The "molecular-mechanical'' model gained in this way is successful in describing the experimentally observed dependencies of the activation energy of the addition reaction on chain length, temperature, and conversion. It also explains the time-conversion behavior of the reaction. Moreover, we gain information about the activation energy of the total reaction and can anticipate the temperature dependency of the chain length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453639
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  • 3
    Electronic Resource
    Electronic Resource
    Model calculation of PDA–PA heterostructures: Influence of topological defects on localized states (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5007-5011 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Model calculations for mixed polydiacetylene (PDA)–polyacetylene (PA) chains are generalized to the inclusion of mobile-soliton-like bond alternation defects. The properties of the midegap state of the solitary defect as well as the influence of the radical electron properties on localized states ("quantum well states'') of the chain are investigated on the basis of a Hückel band structure calculation. It turns out that the quantum well character of the chain strongly depends on the position of the bond alternation defect, e.g., whether it is located on the PA or PDA part of the chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452816
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  • 4
    Electronic Resource
    Electronic Resource
    Fine structure of triplet exciton polarons in polydiacetylene molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 55-62 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Triplet states on conjugated polydiacetylene chains which are created by UV excitation are examined experimentally using ODMR spectroscopy. The observed fine structure shows that the triplet state can be ascribed to the conjugated chain rather than to the side groups and that it is localized. This leads to the suggestion of an exciton polaron. In the theoretical part the wave function of the exciton polaron is calculated using the configuration model in analogy to the description of pz radical electrons on carbene chain ends of reactive short-chain intermediates. The total fine structure tensor is obtained by summing up the fine structure tensors of the individual configurations weighted by their probability densities. The transfer integral t of the configuration model is fitted with respect to good agreement between experimentally observed and calculated fine structure parameters. Finally, comparison between the experimentally observed ESR linewidth and the calculated hyperfine structure splitting shows that the linewidth is motionally narrowed leading to the conclusion that the exciton polaron is mobile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455445
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of π-electron states in polydiacetylene molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1343-1358 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report on π-electron states in polydiacetylene chains using Hückel and self-consistent-field methods (SCF). The Hückel band-structure calculation for the infinitely long chain yields two valence and two conduction bands. The Peierls gap between the upper valence and the lower conduction band is dependent on the bond alternation within the conjugated π system described by a bond alternation parameter −1〈q〈1. It turns out that the acetylene structure (q〉0) is energetically more favorable than the butatriene structure (q〈0). Performing Hückel calculations for short chain polydiacetylene intermediates and including the σ electrons of the polymer backbone by a harmonic potential we obtain the chain length dependency of the bond alternation parameter q. The intermediates with two reactive chain ends (diradicals and dicarbenes) show a transition from the butatriene to the acetylene structure. To determine the spin multiplicity of the ground state of these intermediates we perform a SCF calculation for the singlet and the triplet state of the conjugated π system. According to the experiments we find a singlet ground state for chain lengths of less than six monomer units (diradicals) and a triplet ground state for longer chain lengths (dicarbenes). Optical excitation energies of the short-chain intermediates are determined using the method of Pariser, Parr, and Pople. The qualitative tendencies of the chain length dependency agree well with the experimental results of optical absorption measurements, the absolute values are too high as compared to the experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454206
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic states of the π-radical electron of a carbene chain end on a polydiacetylene chain: Comparison of the configuration model and the continuum model (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1396-1400 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic states of a single pz-radical electron moving on a polydiacetylene chain are described using a simplified version of the configuration model and a quantum mechanical continuum model. The two models are compared by a mathematical transition from the discrete sites of the configuration model to a continuous coordinate. It turns out that the energy difference between the butatriene and the acetylene structure per unit cell is related to the potential gradient of the continuum model. Moreover, the effective mass of the electron, which can be derived from the transfer integral of the configuration model, is about one-half of the real electron mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453268
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  • 7
    Electronic Resource
    Electronic Resource
    Model calculation of PDA–PA heterostructures: Quantum wells in conjugated molecular chains (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2797-2801 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The energy band structures and the corresponding eigenfunctions of polymer chain heterostructures are calculated on the basis of the Hückel theory. The model structure is given by a coupled conjugated polymer system consisting of polydiacetylene (PDA) and polyacetylene (PA) units. The PA–PDA ratio is varied from 0% to 100%. Discrete split-off states within the energy gap and at the exterior of the bands are analyzed with respect to their energies and localization of the corresponding wave function on the PA or PDA units. Criteria for one-dimensional molecular quantum well structures and molecular electronic devices are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451037
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  • 8
    Electronic Resource
    Electronic Resource
    Transient absorption of polydiacetylene molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4429-4434 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: During excitation with ultraviolet light, polydiacetylene crystals show a photoinduced absorption which is ascribed to a triplet excited state of the individual polymer chains. We have measured this absorption using partially and fully polymerized TS and FBS single crystals. The results of stationary and time-resolved experiments are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452855
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  • 9
    Electronic Resource
    Electronic Resource
    Oscillations of the superconducting transition temperature in aluminum films
    Amsterdam : Elsevier
    Physics Letters A 53 (1975), S. 333-335 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(75)90090-0
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  • 10
    Electronic Resource
    Electronic Resource
    Energy gaps and transition temperatures of ultrathin superconducting films
    Amsterdam : Elsevier
    Physics Letters A 47 (1974), S. 47-48 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(74)90100-5
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