^<14>N Nuclear Quadrupole Resonance and Relaxation in 2,5-Dimethyipyrazine : Evidence of Level Crossing between NQR and Tunnel Systems

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概要

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• NQR frequencies and spin-lattice relaxation times (T.) have been measuredfrom 4.2 to 262 K by the pulse method. The quadrupole coupling constant(4.795 MHz) and the asymmetry parameter (0.4964) at 4.2 K are compared withthose in tetramethylpyrazine. The temperature dependence of T. shows peculiarbehavior: Above 200 K, the fluctuation of the electric field gradient dominatesthe relaxation, and the activation energy (E.) of the molecular motion has a valueof 55 f 5 kJ mol -'. Below 100 K, T. is governed by dipolar interactions between"N and 'H. T. minima are observed at 69 K and at 52 K, The methyl-groupreorientation (f.:6.5kJmoI-") contributes to 7'.(min) at 69K, giving thepre-exponential factor of the correlation time, r. ':: 5 x 10 " s. T.(min) at 52 Kis explained with the use of a tentative model of the level crossing between NQRand tunnel systems.

• 社団法人日本物理学会の論文
• 1984-10-15

著者

• Eguchi Taro

  Institute Of Chemistry College Of General Education

• Eguchi Taro

  Institute Of Chemistry College Of General Education Osaka University

• KISHITA Michihiko

  Institute of Chemistry,College of General Education,Osaka University

• Kishita M

  Osaka Univ. Toyonaka Jpn

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• ^N Nuclear Quadrupole Resonance and Relaxation in 2,5-Dimethyipyrazine : Evidence of Level Crossing between NQR and Tunnel Systems
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