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Tytuł:
Effect of Temperature on the Refractive Indices of Liquid Crystals and Validation of a Modified Four-Parameter Model
Autorzy:
Thingujam, K.
Sarkar, S.
Choudhury, B.
Bhattacharjee, A.
Powiązania:
https://bibliotekanauki.pl/articles/1418322.pdf
Data publikacji:
2012-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.15.+e
78.20.Fm
64.70.M-
Opis:
The variation of refractive indices with temperature of three pure nematogenic compounds 5OCB, CPHB and 6CHBT were studied experimentally using thin prism technique. The refractive indices $n_{o}$ and $n_{e}$ were measured using 633 nm lines from a He-Ne laser. A modified four-parameter model was taken which is based on the Vuks equation describing the effect of temperature on the refractive indices of liquid crystals. In this paper we report the variation of refractive indices of these three liquid crystals with temperature, using the thin prism method. The variation in birefringence was determined experimentally. The variation in refractive indices and birefringence were also fitted theoretically using the modified Vuks equation. On comparison, the theoretically fitted values show close agreement with the experimental values.
Źródło:
Acta Physica Polonica A; 2012, 122, 4; 754-757
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Birefringent and Dielectric Properties of [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$ZnBr$\text{}_{4}$ and [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$CdBr$\text{}_{4}$ Crystals
Autorzy:
Sveleba, S.
Mokryi, V.
Polovinko, I.
Kapustyanik, V.
Trybuła, Z.
Petrenko, P.
Kiosse, G.
Kravtsov, V.
Powiązania:
https://bibliotekanauki.pl/articles/1929349.pdf
Data publikacji:
1993-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Ch
77.22.-d
78.20.Fm
64.70.-p
Opis:
Dielectric and birefringent properties of [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$ZnBr$\text{}_{4}$ and [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$CdBr$\text{}_{4}$ crystals were investigated. It has been ascertained that two phase transitions manifest themselves in the temperature dependencies є(T) for [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$CdBr$\text{}_{4}$ crystal - a second-order transition at T$\text{}_{1}$ = 311 K and a first-order one - at T$\text{}_{2}$ = 39 K (∆T$\text{}_{2}$ = 11 K). Besides two earlier known phase transitions in [N(C$\text{}_{2}$H$\text{}_{5}$)$\text{}_{4}$]$\text{}_{2}$ZnBr$\text{}_{4}$ at T$\text{}_{1}$ = 350 K and T$\text{}_{2}^{c\o\ol}$ = 282.8 K (∆T$\text{}_{2}$ ≈ 2.3 K), the additional one was found at T*$\text{}_{2}$ = 287.0 K, both on the cooling and heating runs. On the basis of the data about the peculiarities of dielectric and optical properties in the vicinity of T$\text{}_{2}$ one can made the conclusion about the ferroelectric character of the phase, situated between T*$\text{}_{2}$ and T$\text{}_{2}^{c\o\ol}$.
Źródło:
Acta Physica Polonica A; 1993, 83, 6; 777-784
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Transitions in $[N(CH_3)_4]_2ZnCl_4$ and $[N(CH_3)_4]_2CuCl_4$ Crystals Related with the Incommensurate Modulation Existence
Autorzy:
Sveleba, S.
Semotyuk, O.
Katerynchuk, I.
Kunyo, I.
Karpa, I.
Pankivskyi, Yu.
Powiązania:
https://bibliotekanauki.pl/articles/1812043.pdf
Data publikacji:
2008-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.44.Fw
64.70.Rh
78.20.Fm
65.40.Ba
Opis:
The continuous phase transitions are observed in the crystals with incommensurate phase. They are transitions of parent-incommensurate phases $(T_i)$; transitions between metastable states; incommensurate-commensurate phases $(T_c)$. It was set that phase transition between parent and incommensurate phase is a continuous second-order phase transition with a critical index β = 0.5. The transition between metastable states is a continuous phase transition through the intermediate temperature region - incommensurate phase. The wave vector changes with the temperature here and wave vectorwe q* = q₁ - q₂ appears, where q₁, q₂ denote commensurate values of incommensurability wave vector of neighboring metastable states. It was shown that the phase transition between incommensurate and commensurate phases is a continuous phase transition.
Źródło:
Acta Physica Polonica A; 2008, 114, 4; 791-806
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Stochastic Mode of the Modulated Structure in [N(CH$\text{}_{3}$)$\text{}_{4}$]$\text{}_{2}$MeCl$\text{}_{4}$ Dielectric Crystals
Autorzy:
Sveleba, S.
Semotyuk, O.
Katerynchuk, I.
Furgala, Yu.
Pankivskyi, Yu.
Powiązania:
https://bibliotekanauki.pl/articles/2046819.pdf
Data publikacji:
2006-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.25.Lc
61.44.Fw
64.70.Rh
78.20.Fm
Opis:
Temperature behavior of the optical birefringence in the transitional regions of the incommensurate phase of [N(CH$\text{}_{3}$)]CuCl$\text{}_{4}$ was studied. Temperature dependencies of the modulated structure wave vector and of the specific heat in these regions were analyzed. The stochastic mode of the incommensurate modulated structure in [N(CH$\text{}_{3}$)]MeCl$\text{}_{4}$ (Me = Cu, Fe) dielectric crystals was discovered.
Źródło:
Acta Physica Polonica A; 2006, 109, 6; 695-700
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Linear Dichroism Spectra of Doped Calcium Gallogermanate Crystals
Autorzy:
Shopa, Y.
Ftomyn, N.
Powiązania:
https://bibliotekanauki.pl/articles/1550185.pdf
Data publikacji:
2010-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
78.20.Fm
Opis:
Polarized absorption and linear dichroism spectra of chromium and manganese doped gallogermanate $(Ca_{3}Ga_{2}Ge_{4}O_{14})$ crystals were measured and analyzed. Electronic transitions were identified and crystal field parameters have been determined. The value of linear dichroism obtained at the wavelength of 633 nm was compared with polarimetric measuring data for chromium doped $Ca_{3}Ga_{2}Ge_{4}O_{14}$ crystals.
Źródło:
Acta Physica Polonica A; 2010, 117, 1; 114-116
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Linear Birefringence Anomalies in Crystals of Triglycine Family
Autorzy:
Przesławski, J.
Powiązania:
https://bibliotekanauki.pl/articles/2010959.pdf
Data publikacji:
1999-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.80.Bh
78.20.Fm
Opis:
Temperature dependence of the linear birefringence in TGS crystal family has been studied with a high temperature resolution. Temperature derivatives of the linear birefringence are compared with the specific heat transients measured for triglycine sulphate, triglycine selenate, and triglycine fluoberyllate crystals. Detailed studies revealed an anomaly of the linear birefringence at about 310 K for two cuts (a*- and c-cut) of the TGS crystal.
Źródło:
Acta Physica Polonica A; 1999, 95, 6; 997-1004
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric Polarization of Onsager Fluids. II. Birefringence. 1. Kerr Constants of Pure Substances
Autorzy:
Prezhdo, V. V.
Tarasova, G. V
Prezhdo, O. V.
Tyurin, S. A.
Akulova, O. N.
Kurskaya, T. N
Powiązania:
https://bibliotekanauki.pl/articles/1931288.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Fm
72.80.Jc
Opis:
The Kerr constants of pure liquid organic compounds, which exhibit weak intermolecular interactions and possess widely varying electric, optical and polarizational molecular parameters, were computed from the data on dielectrometry and electric birefringence. Good agreement of the calculated and observed values was reached as the result of the introduction of the local field model, which develops the concepts of reactive field and local electric induction of a polarized fluid, into the orientational theory of the Kerr effect.
Źródło:
Acta Physica Polonica A; 1994, 85, 5; 797-804
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric Polarization of Onsager Fluids. II. Birefringence. 2. Molar Kerr Constants of Binary Solutions
Autorzy:
Prezhdo, V. V.
Tarasova, G. V.
Prezhdo, O. V.
Tyurin, S. A.
Akulova, O. N.
Kurskaya, T. N.
Powiązania:
https://bibliotekanauki.pl/articles/1931555.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Fm
72.80.Jc
31.70.Dk
Opis:
On the ground of dielectrometry and electric birefringence data we calculated molar Kerr constants of substances dissolved in organic media of diverse polarity and polarizability under the conditions of infinite dilution. Minimal errors of the calculated constants, in relation to their gaseous phase values, were achieved as a result of the introduction of the local field model, which evolves the concepts of reactive field and local electric induction of a polarized fluid, into the orientational theory of Kerr effect.
Źródło:
Acta Physica Polonica A; 1994, 86, 3; 327-332
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric Polarization of Onsager Fluids. II. Birefringence. 3. Role of Universal Pairwise Interactions
Autorzy:
Prezhdo, V. V.
Tarasova, G. V.
Prezhdo, O. V.
Tyurin, S. A.
Akulova, O. N.
Ivanov, N. I.
Powiązania:
https://bibliotekanauki.pl/articles/1943971.pdf
Data publikacji:
1996-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.70.Dk
78.20.Fm
72.80.Jc
Opis:
A comparative analysis of several methods of interpretation of solvent influence on molar Kerr constants of solutes was done. The analysis was based on experimentally determined electro-optical and dielectric properties of binary solutions of organic substances with various polarities, polarizabilities and optical anisotropies. It was found that the role of universal van-der-Waals interactions treated via London-Debye-Keesom potentials was best accounted for by a modified orientational theory of Kerr effect that developed the ansatz of reactive field and local dielectric permittivity. An extrapolation method of determination of gas phase molar Kerr constants of solutes was deduced from the theory.
Źródło:
Acta Physica Polonica A; 1996, 89, 1; 47-59
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of the Electro-Optical Kerr Effect in Physical-Chemical Analysis of Binary Systems
Autorzy:
Prezhdo, O. V.
Tyurin, S. A.
Pisarczyk, M.
Odziemek, A.
Prezhdo, V. V.
Powiązania:
https://bibliotekanauki.pl/articles/2030490.pdf
Data publikacji:
2002-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.70.Dk
78.20.Fm
72.80.Jc
Opis:
Applications of the electro-optical Kerr effect in physical-chemical analysis of binary mixtures are reviewed. Improvements in the experimental techniques, in particular, development of the pulsed and alternating electric field based approaches, have led to significant advances in this area. However, problems associated with the description of the internal field of liquids remain and hamper broader applications of the techniques. It is shown that a further progress in the electro-optical Kerr effect characterization of chemical systems relies on the development of a more general theory of optical properties of condensed phase chemical mixtures that can account for nonlinear effects, such as hyperpolarizability, dispersion and specific conditions of the Kerr constant measurements.
Źródło:
Acta Physica Polonica A; 2002, 101, 4; 477-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Role of Intermolecular Interactions in the Electro-Optical Kerr Effect in Liquid Alkanes
Autorzy:
Prezhdo, O. V.
Switek, L.
Zubkova, V. V.
Prezhdo, V. V.
Powiązania:
https://bibliotekanauki.pl/articles/2043659.pdf
Data publikacji:
2005-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.70.Dk
78.20.Fm
Opis:
The electro-optical Kerr effect of n-alkanes from C$\text{}_{5}$ to C$\text{}_{16}$ was investigated in gas phase, liquid phase, and solution. The values of the Kerr constants in gas phase are noticeably distinguishable from those in liquids, where the molecules interact by the London dispersion forces. Both the energy of the dispersion interaction and the difference in the Kerr constants in liquid and gas phase grow with molecular size, indicating the key influence of the interaction on the magnitude of the Kerr effect. Several orientation and molecular-statistical theories of electro-optical Kerr effect were applied to model the change in electro-optical Kerr effect due to the dispersion force. Most theories show significant divergence compared to the experimental data. It is argued that the decisive contribution to electro-optical Kerr effect in liquids and the deviations between the experiment and theory arise due to local liquid structures that collectively orient in the external electric field.
Źródło:
Acta Physica Polonica A; 2005, 108, 3; 429-447
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical and Dilatometric Properties of (CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$Al(SO$\text{}_{4}$)$\text{}_{2}$·6H$\text{}_{2}$O Crystals in Paraelectric and Ferroelectric Phases
Autorzy:
Podsiadła, D.
Czapla, Z.
Andriyevsky, B.
Myshchyshyn, O.
Powiązania:
https://bibliotekanauki.pl/articles/2011078.pdf
Data publikacji:
1999-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Kb
78.20.Fm
Opis:
Experimental investigation of the thermal linear expansion l(T) and temperature dependencies of the interference optical path difference D(T) were carried out for (CH$\text{}_{3}$)$\text{}_{2}$ NH$\text{}_{2}$Al(SO$\text{}_{4}$)$\text{}_{2}$·6H$\text{}_{2}$O crystal, in the range of 120-310 K for three crystal physical directions. Decrease in electrostriction coefficients g of crystal was observed on approaching the phase transition point T$\text{}_{c}$ ≈ 150 K in ferroelectric phase. Relative temperature changes of the lengthening δl/l and refractive index δn/(n-1) are of the same order of magnitude. Peculiarities of temperature dependence of dilatometric and optical parameters of (CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$Al(SO$\text{}_{4}$)$\text{}_{2}$·6H$\text{}_{2}$O testify for qualitative reconstruction of chemical bonds in the crystal when temperature changes in the same phase.
Źródło:
Acta Physica Polonica A; 1999, 96, 3-4; 409-416
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation of Optical Parameters of Liquid Crystals
Autorzy:
Kumar, A.
Powiązania:
https://bibliotekanauki.pl/articles/1814025.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.-e
78.20.Ci
78.20.Fm
77.84.Nh
Opis:
Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.
Źródło:
Acta Physica Polonica A; 2007, 112, 6; 1213-1221
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Linear Birefringence Changes in Betaine Phosphite Crystal
Autorzy:
Kosturek, B.
Przesławski, J.
Czapla, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1929341.pdf
Data publikacji:
1993-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Kb
78.20.Fm
Opis:
Linear birefringence temperature changes are measured in the betaine phoshite crystal. The linear birefringence increments induced by antiferrodistortive, structural and ferroelectric phase transitions are analysed. Temperature derivatives of the linear birefringences are shown for comparison. Critical exponents are determined for both transitions. The antiferrodistortive phase transition is close to a tricritical one.
Źródło:
Acta Physica Polonica A; 1993, 83, 6; 769-775
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and Optical Studies of Homologous Series of Bicyclo[2,2,2]octane Derivatives with -NCS Terminal Group
Autorzy:
Herba, H.
Żywucki, B.
Czechowski, G.
Bauman, D.
Wąsik, A.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933452.pdf
Data publikacji:
1995-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Gd
77.22.Ch
78.20.Fm
Opis:
The static dielectric constants and the optical birefringence for four members of the homologous series of bicyclo[2,2,2]octane derivatives with -NCS terminal group (pentyl to octyl) have been measured as a function of temperature. From the dielectric anisotropy, the optical birefringence as well as the polarized absorption spectra of the dichroic dye dissolved in the liquid crystalline host the order parameter has been determined. The results obtained by using various experimental methods have been compared with those calculated from the Maier-Saupe mean field theory. It has been found that the order parameter for the successive homologues shows alternation similar to that exhibited for the nematic-isotropic transition temperature.
Źródło:
Acta Physica Polonica A; 1995, 87, 6; 985-994
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 21

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