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1Author    J. Wąsicki, Z. Pająk, A. KozakRequires cookie*
 Title    Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate  
 Abstract    Temperature dependences of and 19 F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equiva-lent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10~ 10 s. 
  Reference    Z. Naturforsch. 45a, 33—36 (1990); received August 5 1989 
  Published    1990 
  Keywords    NMR, cross-relaxation, molecular motions, phase transitions 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0033.pdf 
 Identifier    ZNA-1990-45a-0033 
 Volume    45 
2Author    Z. Szafrańska, A. Pająk, KozakRequires cookie*
 Abstract    Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetrabutylammonium tetrafluoroborate have been measured over a wide range of temperatures at several Larmor frequencies. An analysis of cross-relaxation effects results in a determination of activation parameters for anion and cation reorientations. Three solid phases characterized by different ion dynamics are evidenced. M o le c u la r M o tio n in S o lid T e tra b u ty la m m o n iu m T e tr a f lu o r o b o r a te 
  Reference    Z. Naturforsch. 46a, 545—550 (1991); received March 14 1991 
  Published    1991 
  Keywords    NMR, Cross-relaxation, Molecular motions, Phase transitions 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0545.pdf 
 Identifier    ZNA-1991-46a-0545 
 Volume    46 
3Author    David StephensonRequires cookie*
 Title    Two-dimensional Two Contact Double Resonance Spectroscopy  
 Abstract    A two-dimensional spectroscopic technique is presented. Application of the technique to de-termine all the relaxation rates for a multi-level quadrupole system is discussed along with ex-perimental requirements. Theoretical and experimental data are analyzed for the 14 N, three level, spin 1 system. The analysis shows that all three relaxation rates can be obtained from a single two-dimensional spectrum, and that only 3 peaks in the 3 x 3 two-dimensional intensity matrix are needed to completely specify the problem. The 4-level spin 3/2 system is also examined. In theory, all six relaxation rates can be independently evaluated (for a suitable system) without necessitating measurement at the low frequency Zeeman separated levels. 
  Reference    Z. Naturforsch. 55a, 79—82 (2000); received September 11 1999 
  Published    2000 
  Keywords    NQR, 14 N, Relaxation, Two-dimensional, Cross-relaxation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0079.pdf 
 Identifier    ZNA-2000-55a-0079 
 Volume    55 
4Author    Hiroyuki IshidaRequires cookie*
 Title    H NMR Study of Ionic Motions in High Temperature Solid Phases of (CH 3 NH 3 ) 2 ZnCl 4  
 Abstract    The reorientation of the tetrahedral complex anion ZnCl 4 2-and the self-diffusion of the cation in (CH 3 NH3) 2 ZnCl4 were studied by 'H NMR spin-lattice relaxation time ('H T X) experiments. In the second highest-temperature phase, the temperature dependence of *H T X observed at 8.5 MHz could be explained by a magnetic dipolar-electric quadrupolar cross relaxation between 'H and chlorine nuclei, and the activation energy of the anion motion was determined to be 105 kJ mol -1 . In the highest-temperature phase, the activation energy of the self-diffusion of the cation was determined to be 58 kJ mol -1 from the temperature and frequency dependence of 'H T X . 
  Reference    Z. Naturforsch. 55a, 412—114 (2000); received January 8 2000 
  Published    2000 
  Keywords    Nuclear Magnetic Resonance, Molecular Motion, Cross Relaxation, (C^N^^ZnCfj 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0412.pdf 
 Identifier    ZNA-2000-55a-0412 
 Volume    55 
5Author    G. Sulzer, B. Itterm, E. Diehl, B. Fischer, H.-P Frank, E. Jäger, W. Seelinger, H.-J Stockmann, H. AckermannRequires cookie*
 Title    Temperature Dependence of Impurity Induced EFG's in Extremely Diluted CuB  
 Abstract    The temperature dependence of impurity induced EFG 's around implanted 12B ions in Cu was measured for two lattice locations using the ß-N M R method. The induced EFG at the nearest neighbouring host atoms decreases with increasing temperature for the case of 12B stopped on interstitial sites, whereas the opposite temperature behaviour was found if 12B is situated in substi­ tutional sites. 
  Reference    Z. Naturforsch. 49a, 354 (1994); received July 23 1993 
  Published    1994 
  Keywords    N M R, ß radiation detected, Cross relaxation, Electric field gradient, Temperature dependence o f EFG, Impurity induced EFG 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0354.pdf 
 Identifier    ZNA-1994-49a-0354 
 Volume    49