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1999 (3)
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1987 (1)
1Author    R. BlincRequires cookie*
 Title    NQR in Dipolar and Quadrupolar Glasses  
 Abstract    It is shown that nuclear quadrupole resonance and quadrupole perturbed magnetic resonance represent a powerful technique to determine the local polarization distribution and its second moment, the Edwards-Anderson order parameter, in proton and deuteron glasses. For quadrupolar glasses the local orientational distribution function can be determined from the inhomogeneous NMR or NQR lineshape, thus allowing for a measurement of the quadrupolar Edwards-Anderson order parameter. The comparison of the temperature dependences of the thus obtained order parameters with theoretical predictions then allows for a discrimination between the different possible models of the glassy transition. 
  Reference    Z. Naturforsch. 45a, 313—322 (1990); received August 22 1989 
  Published    1990 
  Keywords    NQR, Glasses, Order parameters 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0313.pdf 
 Identifier    ZNA-1990-45a-0313 
 Volume    45 
2Author    Hanka Moryson, Danuta Bauman, Wojciech Hilczer, Stanislaw HoffmannRequires cookie*
 Title    Molecular Orientation in Uniaxial Liquid Crystal Phases as Studied by Electron Paramagnetic Resonance  
 Abstract    The electron paramagnetic resonance spectra of 3/3-doxyl-5a:-cholestane dissolved in five liquid crystals have been recorded as a function of temperature in the isotropic and mesogenic phases. From these spectra the order parameter (P2) has been determined. The results have been com-pared with the data obtained from the optical birefringence measurements and from the polarized absorption spectra of the dichroic dye dissolved in liquid crystal host. 
  Reference    Z. Naturforsch. 54a, 299—304 (1999); received March 31 1999 
  Published    1999 
  Keywords    Liquid Crystal, EPR, Order Parameter 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0299.pdf 
 Identifier    ZNA-1999-54a-0299 
 Volume    54 
3Author    A. Würflinger, S. UrbanRequires cookie*
 Title    Relations between Nematic Potential and Order Parameters (P 2 ) and (P 4 >  
 Abstract    The Maier-Saupe theory is employed in order to calculate order parameters (P 2), (P 4) from the nema-tic potential q. The relation between <r=q/(RT) and S = (P 2) corresponds well with a recently establis-hed formula by Kalmykov. The relation between the order parameters is in accordance with the analy-tic expression (P 4)=5/l (P 2) 2 proposed by Zanonni, but deviates significantly from the Faber model, according to which log (P 4)=(10/3) log (P 2). Experimental results for 5 CB obtained from Raman mea-surements, however, are in better agreement with the Faber model. 
  Reference    Z. Naturforsch. 53a, 883—886 (1998); received September 12 1998 
  Published    1998 
  Keywords    Liquid Crystals, Nematic Potential, Order Parameters 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0883.pdf 
 Identifier    ZNA-1998-53a-0883 
 Volume    53 
4Author    Phineus Markwick, Stanislaw Urban, Albert WürflingerRequires cookie*
 Title    High Pressure Dielectric Studies of 8CB in the Isotropic, Nematic, and Smectic A Phases  
 Abstract    The static and complex permittivity of 4-n-octyl-4'-cyanobiphenyl (8CB) has been measured for the isotropic, nematic and smectic A phases as functions of temperature and pressure. The ranges of 297 -361 K, 0.1 -220 MPa, and 0.1 -13 MHz, were covered. Only the parallel component of the complex permittivity, £*(/) = e'(f) — ie"(f), was measured. The relaxation times T||(p, T) as well as ris(p, T) were analysed at constant temperature, pressure and volumes yielding the activation volume, A ¥ V(T), activation enthalpy A^H(p), and activation energy lyU(V), respectively. All activation parameters calculated for the smectic A phase of 8CB are smaller than those obtained for the nematic phase. The activation energy constitutes approximately half of the activation enthalpy value in all three phases studied. The pressure study allowed to calculate the pressure dependence of the retardation factor g\\(p, T), from which the nematic potential q(p,T) can be derived. Using the relationships between g\\ and q/RT proposed by Kalmykov and Coffey, the order parameter (Piip, T)) was calculated as a function of pressure. 
  Reference    Z. Naturforsch. 54a, 275—280 (1999); received March 13 1999 
  Published    1999 
  Keywords    Liquid Crystals, 8CB, High Pressure, Dielectric, Thermodynamics, Order Parameter 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0275.pdf 
 Identifier    ZNA-1999-54a-0275 
 Volume    54 
5Author    S. UrbanRequires cookie*
 Title    Dielectric Studies of 4-w-Hexyloxy-4'-Cyanobiphenyl (60CB) at Elevated Pressure  
 Abstract    The principal dielectric permittivity components in the nematic phase of 4-rc-hexyloxy-4'-cyanobiph-enyl (60CB) were measured as functions of temperature at ambient pressure and as functions of pres-sure up to 100 MPa at several constant temperatures. The dielectric anisotropy is analized in the frame of the Maier-Meier equations. The pressure dependence of the order parameter is deduced. Preliminary results for the activation volume and activation enthalpy from the pressure and temperature dependenc-es of the longitudinal relaxation times are obtained. 
  Reference    Z. Naturforsch. 54a, 365—369 (1999); received March 29 1999 
  Published    1999 
  Keywords    Nematic Liquid Crystal, 60CB, Dielectric Anisotropy, Order Parameter, High Pressure 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0365.pdf 
 Identifier    ZNA-1999-54a-0365 
 Volume    54 
6Author    B. KirsteRequires cookie*
 Title    EPR and ENDO R Investigations of a Cholestane Spin Probe in Liquid Crystals  
 Abstract    A detailed EN D O R study o f anisotropic proton hyperfine shifts in the nitroxide spin probe 3-doxylcholestane (CSL) in liquid-crystalline solution is described. The data are interpreted by means o f theoretically calculated proton hyperfine tensors (M cConnell-Strathdee-Derbyshire treatment), providing an independent check o f the ordering matrix. The orientational order and the dynamic behavior o f the nematic and smectic phases o f the liquid crystals (40,6), (50,6), and 8CB are investigated by EPR using CSL and phenalenyl as spin probes. 
  Reference    Z. Naturforsch. 42a, 1296—1304 (1987); received August 8 1987 
  Published    1987 
  Keywords    EPR, EN D O R, liquid crystal, order parameters, sm ectic phase 
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 TEI-XML for    default:Reihe_A/42/ZNA-1987-42a-1296.pdf 
 Identifier    ZNA-1987-42a-1296 
 Volume    42