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'Molecular motion' in keywords Facet   Publication Year 1990  [X]
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1990[X]
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    I. A. Kjuntsel, V. A. Mokeeva, I. G. Shaposhnikov, G. B. SoiferRequires cookie*
 Title    Influence of Thermoactivated Molecular Motions on the 35 C1 Quadrupole Relaxation  
 Abstract    The effect on the 35 C1 quadrupole relaxation of modulations of the electric field gradient by thermally activated motions of nearby nonbonding symmetric and asymmetric atomic groups has been investigated. This way the activation energy of the motions has been determined and the fraction of the electric field gradient influenced by the motions has been estimated. This fraction can be taken as a measure of the intensity of nonbonding interactions in solids. 
  Reference    Z. Naturforsch. 45a, 531—535 (1990); received August 23 1989 in revised form December 8 1989 
  Published    1990 
  Keywords    Molecular motion, Modulation effect, Nuclear quadrupole relaxation 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0531.pdf 
 Identifier    ZNA-1990-45a-0531 
 Volume    45