Order parameters from U.V. spectra with incompletely polarized absorption bands

Kuball, H.‐G.; Memmer, R.; Strauss, A. J.; Junge, Matthew; Scherowsky, G.; Schönhofer, Alfred

doi:10.1080/02678298908026402

Cited by 21 publications

(10 citation statements)

References 6 publications

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“…The molecular decadic absorption coefficients for light polarized parallel (ε 1 ) and perpendicular (ε 2 ) to the optical axis of a uniaxial sample are given by , are the absorption coefficients for light beams polarized linearly parallel to the axes in a completely oriented system. The axes are the principal axes of the absorption tensor ε i j . − a i j are the elements of the orthogonal matrix which transforms the coordinates into the coordinates. The coordinates refer to the common principal axes of the order tensors g i j k k ( k = 1, 2, 3) and the following convention for numbering the axes is used: ≥ ≥ with as the “orientation axis”.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…In order to obtain information about the order parameters and the directions of the transition moments responsible for the given absorption band from the linear dichroism, we used the method described in detail previously. ,,, This method was elaborated for the case where one purely polarized band (at ν̄ 1 ) and another band (at ν̄ 2 ) with mixed polarization exist in the absorption spectrum, for molecules with and coordinate systems coinciding by symmetry. Thus, it is not directly applicable to molecules with, e.g., the point symmetry group C 2 .…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Linear and Circular Dichroism Spectroscopic Study of β,β‘-Dimethylmesobilirubin-XIIIα Oriented in a Nematic Liquid Crystal

et al. 1996

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(βR,β‘R)-dimethylmesobilirubin-XIIIα, an optically active synthetic analogue of bilirubin, the yellow pigment of jaundice, and xanthobilirubinat, a dipyrrinone analogue for one-half of a rubin pigment, dissolved in the nematic liquid crystal ZLI 1695, have been studied by means of UV−vis polarized absorption and circular dichroism (CD) spectroscopy. The order parameters have been evaluated from the temperature dependence of the degree of anisotropy. The method of “vanishing spectral features” has also been taken into consideration. The reduced absorption spectra have been obtained. It has been found that the orientational properties as well as the polarization of the absorption bands of the two compounds are quite different. Moreover, the UV−vis absorption and CD spectra of β,β‘-dimethylmesobilirubin-XIIIα have been interpreted on the basis of the exciton coupling model, assuming the point symmetry group C 2. The orientation of the principal axes of the orientational distribution tensor (order tensor) with respect to the molecular frame has been determined. That the anisotropic CD (ACD) spectra are not very different from the CD spectra can be understood from the spectroscopic analysis taking into account the orientational order.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Theoretical Backgroundmentioning

confidence: 99%

Linear and Circular Dichroism Spectroscopic Study of β,β‘-Dimethylmesobilirubin-XIIIα Oriented in a Nematic Liquid Crystal

et al. 1996

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“…As a host, 4-octylspectroscopy and the physics of liquid crystals. In the 4¾ -cyanobipheny l (8CB) was chosen, while two dichroic former area, such investigations give information condyes: a blue azo dye [18,19] and a yellow naphthalenecerning the electronic spectra of the dyes [3][4][5][6][7][8][9], and benzimidazole derivative with excellent uorescent in the latter they enable a better understanding of the properties [18] were used as guest species. intermolecular forces in anisotropic media.…”

Section: Introductionmentioning

confidence: 99%

Alignment of liquid crystal and dichroic dye molecules in mixed Langmuir and Langmuir-Blodgett films

Martyński¹,

Biadasz²,

Bauman³

2002

Liquid Crystals

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A study of dichroic dye-liquid crystal mixtures (guest-host systems) in monolayers formed at a gas-liquid interface (Langmuir lms) and at a solid surface (Langmuir-Blodgett lms) has been made. As a host 4-n-octyl-4¾ -cyanobiphenyl (8CB) or 4-n-pentyl-4 ² -cyano-p-terphenyl (5CT) were chosen, while three dichroic azo dyes with various molecular structures were used as guest species. The dyes were added to the liquid crystal matrices at a concentration corresponding to the whole range of molar fractions and the surface pressure-mean molecular area isotherms for Langmuir lms were recorded. On the basis of the isotherms, conclusions about the molecular organization and the miscibility of the components in the ultrathin lms were drawn. The Langmuir lms were transferred onto the quartz plates at surface pressures below the collapse point. The polarized absorption spectra of the Langmuir-Blodgett lms were recorded and information about the alignment and intermolecular interactions in the mixtures of the non-amphiphilic dichroic dyes and the liquid crystals with strongly polar terminal groups were obtained.

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“…(1)] are zero and hence so are the odd parameters. In order to study the orientational behaviour of liquid crystals, the classical methods of molecular spectroscopy, i.e., magnetic resonances [4,5] and optical spectroscopy with polarized light [6][7][8][9][10][11][12][13] have been widely applied. Linearly polarized light is of special interest as it represents a powerful tool for study of oriented assemblies of molecules [14].…”

Section: Introductionmentioning

confidence: 99%

Oriental behaviour of some homologues of 4-n-pentyl-phenylthio-4′-n-alkoxybenzoate doped with dichroic dye

Bauman

Zięba

Mykowska

2008

Opto-Electronics Review

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The long-range orientational order of three members of 4-n-pentylphenylthio-4′-n-alkoxybenzoate $$ (\bar nS5) $$ series doped with a dichroic dye was studied by means of electronic absorption and fluorescence measurements. The order parameters <P2> and <P4> as well as the orientational distribution function were determined on the basis of absorption and emission spectra of linearly polarized light recorded as a function of temperature in the nematic, smectic A, and smectic C phases. An influence of the dye molecular structure on the orientational order of the dye/liquid crystal mixture was observed. Moreover, the dependence of the order parameter values on the length of the alkoxy chain in liquid crystal molecules was found. It was shown that the order parameter <P4>, obtained from fluorescence measurements, can be helpful in recognizing the second-order or weakly first-order transitions between various liquid crystalline phases.

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Order parameters from U.V. spectra with incompletely polarized absorption bands

Cited by 21 publications

References 6 publications

Linear and Circular Dichroism Spectroscopic Study of β,β‘-Dimethylmesobilirubin-XIIIα Oriented in a Nematic Liquid Crystal

Linear and Circular Dichroism Spectroscopic Study of β,β‘-Dimethylmesobilirubin-XIIIα Oriented in a Nematic Liquid Crystal

Alignment of liquid crystal and dichroic dye molecules in mixed Langmuir and Langmuir-Blodgett films

Oriental behaviour of some homologues of 4-n-pentyl-phenylthio-4′-n-alkoxybenzoate doped with dichroic dye

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