Наукові публікації кафедри загальної та прикладної фізики

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Browsing Наукові публікації кафедри загальної та прикладної фізики by Subject "absorption"

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    Mechanism of dimerization of viologens in liquid crystalline medium
    (Ukr. J. Phys. 2017. Vol. 62, No. 4 294-298, 2017) Bordyuh, Hanna
    This work presents the analysis of experimental data on electrooptical properties of viologens incorporated into the liquid crystalline medium. These data along with theoretical considerations allow specifying the mechanism, which leads to the double color change in the liquid crystal – viologen samples stipulated by the application of increasing voltage values. Specifically, it is proved that the first color change takes place due to the one-electron reduction of viologen molecules, and the second color change is caused by the dimerization between viologen molecules, which were fully reduced under the action of a voltage applied, and initial viologen molecules.
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    Mechanism of dimerization of viologens in liquid crystalline medium
    (Національний Авіаційний Університет, 2015) Bordyuh, Hanna
    This work presents the analysis of experimental data on optical properties of viologens introduced to the liquid crystalline medium stipulated by the application of increasing voltage values. These data along with quantum mechanical theory allowed to specify the mechanism of dimerization of violoden molecules which leads to the colour change of the liquid crystal-viologen sample. Specifically, the dimerization of viologen molecules in liquid crystalline medium occurs due to interaction between viologen molecules, which were fully reduced under the action a voltage applied, and initial viologen molecules.
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    Nonlinear optical response of smectic structure glasses based on cobalt alkanoates
    (IEEE, 2010, 2010) Gridyakina, Alexandra
    Nonlinear-optical response of metal-alkanoates anisotropic glasses based on cobalt-alkanoate was studied using method of the dynamic holography. Fundamental optical (refractive index and absorption coefficient) and nonlinear-optical (nonlinear susceptibilities and polarizabilities) parameters of the mesomorphic glasses based on cobalt-alkanoates can be tuned via varying chain length anion (interlayer distance of homologous lines) and\or by changing of the cation composition (exploiting binary or ternary systems).
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    Structure and Intermolecular Interactions in Ionic Liquid Crystals Doped with Electrochromic Viologen
    (Russian Journal of Physical Chemistry, Vol. 79, Suppl. 1, 2005, pp. S66–S70, 2005) Bordyuh, Hanna; Polishchuk, Arkadiy
    The results of an investigation of structural and electrooptical properties of potassium caprylate lyotropic liquid crystals (LCs) doped with electrochromic viologen are presented. The samples are colored when an electric field is applied. The color deepens with the voltage applied, and relevant features appear in electronic absorption spectra. Two stages may be recognized in the processes that occur in a sample in the field. The first stage (at 2–2.5 V) involves the formation of radical cations (RCs) from viologen molecules, which makes the samples blue (two absorption bands appear at wavelengths of 395 and 610 nm in optical spectra). At the second stage (at 3.5–4 V), the radical cations are dimerized, and the sample becomes red (the spectra show bands in the region of 365 and 520 nm). Absorption in a lyotropic LC increases with the viologen concentration increasing from 1 to 2 to 4%. Small-angle X-ray scattering was measured on unoriented samples of pure potassium caprylate with thicknesses ranging from 30 μm to 1 mm. In all samples, a smectic order was observed in lyotropic ionic LC (LILC). From the X-ray scattering data, the bilayer thickness and the smectic correlation length were computed. It was inferred that viologen molecules, when present in low concentrations (1–4%), are organically incorporated into the matrix without spoiling the layer order intrinsic to the matrix.