| 1 | Author
| R. Blinc | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0313.pdf | | | Identifier
| ZNA-1990-45a-0313 | | | Volume
| 45 | |
3 | Author
| A. Würflinger, S. Urban | Requires 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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| default:Reihe_A/53/ZNA-1998-53a-0883.pdf | | | Identifier
| ZNA-1998-53a-0883 | | | Volume
| 53 | |
4 | Author
| Phineus Markwick, Stanislaw Urban, Albert Würflinger | Requires 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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| default:Reihe_A/54/ZNA-1999-54a-0275.pdf | | | Identifier
| ZNA-1999-54a-0275 | | | Volume
| 54 | |
6 | Author
| B. Kirste | Requires 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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| default:Reihe_A/42/ZNA-1987-42a-1296.pdf | | | Identifier
| ZNA-1987-42a-1296 | | | Volume
| 42 | |
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