NMR Study of Phase Transitions in Betaine Phosphite (CH_3)_3NCH_2COOH・H_2PO_3

概要

論文の詳細を見る
The phase transitions in (CH_3)_3NCH_2COOH・H_2PO_3 at T_<C1> = 355 K and at T_<C2> = 216K were studied by nuclear magnetic resonance. Spin-lattice relaxation time T_1 of the ^<13>C nucleus in the CH_3 group shows two-mode behavior without showing anomaly in the both phase transitions. Activation energies are determined to be 23.1(9) and 1.3(2) kJmol^<-1> for two modes T_1 of the ^<13>C nucleus in the CH_2 group exhibits a shallow dip around T_<C1>, suggesting that the motion of the CH_2 group slows down more or less at T_<C1> T_1 of the ^<31>P nucleus takes a minimum at 253 K and activation energy is obtained as 12.6(2) kJmol^<-1>. In addition to the T_1 minimum, this shows a sharp dip at T_<C1> due to the critical slowing-down of the HPO_3^<2-> motion. The incomplete slow-down of the CH_2 motion is considered to be induced by the coupling with the disorder of the HPO_3^<2-> anion. The critical relaxation rate of the ^<31>P nucleus is well reproduced by the quasi-one-dimensional. Ising model Interaction parameters for intrachain J_‖ and interchain J_⊥ are determined to be 567(1) and 28 4(4) K (J_⊥/ J_‖ = 0.05), respectively.
社団法人日本物理学会の論文
2003-09-15