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  • 1
    Electronic Resource
    Electronic Resource
    Local Density Functional Study of Copper Clusters: A Comparison between Real Clusters, Model Surface Clusters, and the Actual Metal Surface (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 349-360 
    Details
    ISSN: 1434-1948
    Keywords: Copper clusters ; Cu(100) surface ; Chemical hardness ; Relaxation energy ; Size effect ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Density Functional Theory is used to study the influence of the size of copper clusters modeling the Cu(100) surface, on the electronic properties: ionization potential, electron affinity, electronic chemical potential, and chemical hardness. The model clusters are chosen to have a bilayer structure and range in size from 9 to 20 copper atoms. The chemical hardness being identified as the relaxation energy of the frontier levels when an electron is removed or added to the system, a simple expression is proposed to estimate its value from the eigenenergies of the frontier levels in neutral and partially ionized systems. A detailed comparison of the geometric and electronic structures is made between the model surface copper clusters, real copper clusters, and the actual metal surface; it is seen that the model surface clusters provide an easy extrapolation to the properties of the metal surface.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Bis(1,3-dithiole) Polymethine Dyes for Third-Order Nonlinear Optics - Synthesis, Electronic Structure, Nonlinear Optical Properties, and Structure-Property Relations (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2747-2757 
    Details
    ISSN: 1434-193X
    Keywords: Polymethines ; Dyes ; Electronic structure ; Nonlinear optics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a series of new sulfur-containing polymethine dyes is reported. The linear optical properties of these bis(1,3-dithiole) (mono-, tri-, penta-, and hepta-)methine dyes show intense and narrow optical absorptions typical of cyanine dyes. The absorption maximum is increasingly red-shifted from 489 nm for the monomethine dye to 911 nm for the heptamethine compound. Based on third-harmonic generation measurements at fundamental wavelength between 1064 nm and 1907 nm, γ values were evaluated to lie in the range between 1·10-33 e.s.u. and 14·10-33 e.s.u. showing that the nonlinear response of the bis(1,3-dithiole) polymethine dyes compare well with other organic π-electron systems of similar size. Comparisons of the experimental values of γ to calculated static values obtained by ab initio and semiempirical calculations (AM1, PM3) have been made as well as comparisons to dynamic values estimated from a free-electron model. The computed dynamic values can be described by a power law; γ ≈ L5 where L denotes the length of the molecules. Our studies confirm the stabilizing effect of a carbocyclic ring in the cyanine backbone making the heptamethine dye an unusually stable and highly nonlinear polymethine chromophore possessing a strong NIR optical transition and very good transparency in the visible region.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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