Browsing by Author "Wilckens, Rudolf"

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    Comparative optical investigations on the one-dimensional organic metals (perylene)2(PF6)1.1x0.8CH2Cl2, (pyrene)12(SbF6)7 and fluoranthene)2(AsF6)0.2(PF6)0.8
    (1983) Geserich, Hans Peter; Wilckens, Rudolf; Ruppel, Wolfgang; Enkelmann, Volker; Wegner, Gerhard; Wieners, Gerhard; Schweitzer, Dieter; Keller, Heimo J.
    The reflectance spectra of different radical cation salts of the type (arene)2XF6 are reported (X=P, As, Sb). For light polarised perpendicular to the molecular stacks, the crystals exhibit the optical behaviour of an insulating molecular crystal, whereas for light polarised parallel to the stacks a pronounced plasma edge is observed. Compared to other organic metals the crystals show remarkably high values of the plasma energy. Because the concentration of the free carriers is obtained from the charge transfer between the radical cations and the inorganic counter ions, the effective mass of the free carriers may be calculated from the plasma frequency. The analysis of the reflectance data by a Lorentz-Drude model yields as well the values of the mean collition time, the electrical conductivity, and the bandwith.
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    ItemOpen Access
    Highly conducting perylene radical salts
    (1982) Koch, P.; Schweitzer, Dieter; Harms, Ralf H.; Keller, Heimo J.; Schäfer, Herbert; Helberg, Hans W.; Wilckens, Rudolf; Geserich, Hans Peter; Ruppel, Wolfgang
    Temperature dependent dc and microwave conductivity data together with EPR and optical reflectance measurements on the "mixed" system (pe)2(ASF6)0,75(PF6)0,35 times 0,85 CH2Cl2 are described. The data prove metallic behaviour of this organic solid down to 200 K.
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    ItemOpen Access
    Plasma reflectance of the one-dimensional organic metals of the type (arene)2XF6(arene=perylene, pyrene or fluoranthene ; X=P, As, Sb)
    (1983) Geserich, Hans Peter; Koch, Bertram; Ruppel, Wolfgang; Wilckens, Rudolf; Schweitzer, Dieter; Enkelmann, Volker; Wegner, Gerhard; Wieners, Gerhard; Keller, Heimo J.
    We have investigated the spectral position and the form of the plasma edge of different radical cation salts of the type (arene)zXF, independence of the type of the organic donor molecule, and of the charge transfer between donor and acceptor molecules.
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    Spectral reflectance of the one-dimensional organic metals (perylene)2(PF6)1.1 × 0.8CH2Cl2 and (perylene)2(AsF6)1.1 × 0.7CH2Cl2
    (1982) Wilckens, Rudolf; Geserich, Hans Peter; Ruppel, Wolfgang; Koch, P.; Schweitzer, Dieter; Keller, Heimo J.
    We report on the optical reflectance of (perylene)2(PF6)1.1 × 0.8CH2Cl2 and (perylene)2(AsF6)1.1 × 0.7CH2Cl2 single crystals in the energy range from 0.25 to 4 eV. For light polarized perpendicular to the molecular stacks the crystals exhibit the optical behaviour of an insulating molecular crystals, whereas for light polarized parallel to the stacks a pronounced plasma edge at hω=0,9eV image is observed. The experimental data were analyzed by a Lorentz-Drude model in order to determine the electrical conductivity, the carrier concentration, the effective mass, the collision time, the band width, and the Fermi vector of the crystals.