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1996 (1)
1994 (1)
1Author    Tetsuo Asaji, Masaki Ohkawa, Takehiko Chiba, Makoto KagaRequires cookie*
 Title    Successive Phase Transitions in Potassium Hexachloroselenate(IV) Revealed by 35 C1 NQR  
 Abstract    K 2 SeCl 6 undergoes structural phase transitions of first order at 35 K, 65 K, and 79 K. The temperature dependence of the ? C1 NQR spin-lattice relaxation time suggests that the phase transitions at 65 K and 79 K are displacive ones associated with a resonant soft mode. The presence of a precursor cluster is suggested by the temperature dependence of the signal intensity above 79 K. 
  Reference    Z. Naturforsch. 51a, 705—709 (1996); received October 20 1995 
  Published    1996 
  Keywords    Phase transition, Soft mode, NQR, Spin-lattice relaxation 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0705.pdf 
 Identifier    ZNA-1996-51a-0705 
 Volume    51 
2Author    Tetsuo Asaji, Hideshi Tomizawa, Ryuichi IkedaRequires cookie*
 Title    Structural Phase Transition of N,N-Dimethylnitramine as Studied by 14N Nuclear Quadrupole Resonance  
 Abstract    The 14N nuclear quadrupole relaxation time and resonance frequencies v+, v_, and vd of N,N-dimethylnitramine were measured between 14 and 313 K. The frequency increase of v+ and v_ observed below Tc (108 K) is explained by the increase o f prc electrons in the am ino nitrogen caused by the deformation of the m olecular skelton, which is planar above Tc. The sharp Tip minima for v+ and v_ observed at Tc are attributed to the softening o f vibration modes on both sides of Tc. The fluctuation o f the nitrogen-hydrogen m agnetic dipolar interaction due to C H 3 reorientation was detected as a broad T'lQ minimum observed around 84 K. A logarithmic divergence of Tu31 observed on the high-temperature side o f Tc suggests the presence o f a diffusive or overdamped-type soft mode. 
  Reference    Z. Naturforsch. 49a, 253 (1994); received August 10 1993 
  Published    1994 
  Keywords    M olecular crystal, Phase transition, Soft mode, NQ R, Spin-lattice relaxation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0253.pdf 
 Identifier    ZNA-1994-49a-0253 
 Volume    49