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1994 (2)
1Author    C. Forte, M. Geppi, C. A. VeraciniRequires cookie*
 Title    Study of the Molecular Dynamics from Deuterium Zeeman and Quadrupolar NMR Relaxation of 4,4'-di-n-Heptylazoxybenzene in the Nematic and Smectic A Phases  
 Abstract    The deuterium spin-lattice (T1Z) and quadrupolar (r iQ) relaxation times of the liquid crystal 4,4'-Heptyl-azoxybenzene (HAB), deuterated on the aromatic rings and the first methylene group of the chains, have been measured by means of the Jeener-Broekaert pulse sequence at two different frequencies (10 and 46.04 M Hz) and throughout the nematic and the smectic A phase. By applying suitable models, we have determined rotational and reorientational diffusion coefficients and evalu­ ated the contribution of the different m otions (internal, molecular and collective) to the relaxation. In particular we have found a non negligible contribution from order director fluctuations. A comparison between the Tlz and Ti Q measurements performed by means of Jeener-Broekaert and Wimperis pulse sequences is also shown. 
  Reference    Z. Naturforsch. 49a, 311 (1994); received August 16 1993 
  Published    1994 
  Keywords    Liquid crystal, Deuterium N M R, M olecular dynamics, Deuterium relaxation, Director fluctuation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0311.pdf 
 Identifier    ZNA-1994-49a-0311 
 Volume    49 
2Author    N. Obuo, N. Akam UraRequires cookie*
 Title    Nuclear Quadrupole Interaction and Ionic Dynamics in Sodium Superionic Conductors  
 Abstract    Recent work on the 23N a quadrupole interaction in the N A SIC O N family is reviewed. The applicability and the lim itation of the two-dim ensional nutation N M R to complex systems with more than one quadrupolar nuclear sites is discussed and the possibility of sodium ion exchange in som e of the N A SIC O N -type com pounds is pointed out. The microscopic mechanism of the site exchange is examined by m olecular dynamics simulation. A model potential energy function for the site exchange and /or hopping transport o f the sodium ions is proposed. It interprets qualitatively the difference between the activation energies deduced by N M R and by conductivity measurement. 
  Reference    Z. Naturforsch. 49a, 337 (1994); received O ctober 23 1993 
  Published    1994 
  Keywords    N utation N M R, Q uadrupole effect, Superionic conductor, N A SIC O N, Chemical ex­ change, M olecular dynamics 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0337.pdf 
 Identifier    ZNA-1994-49a-0337 
 Volume    49