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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