Nuclear Spin Diffusion, Cross Relaxation and Longitudinal Relaxation in Solid HD with Dilute H_2
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概要
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Concentration dependences of the longitudinal nuclear relaxation time T_1 in solid HD with dilute H_2 are theoretically studied at ortho-H_2 Concentrations, x_0, 2×10^<-2> to 10^<-4>. It is proved that the cross relaxation combined with the spin, diffusion has an important effect on T_1. The lowest relaxation constant for the nuclear magnetization in the spherical region of HD medium with an ortho-H_2 at the center is obtained by solving a homogeneous integral equation. The resultant T_1 is studied by the two methods of approximations, the mean volume approximation (MVA) and the constant relaxation time approximation (CRTA). T_1 can be expressed in terms of the configuration average of the relevant quantity in CRTA.The cross relaxation rate and the spin diffusion constant are evaluated from the first principle. By using the spectral density function obtained previously both MVA and CRTA are shown to give almost the same result for T_1, Which is in agreement with experiments at concentrations down to 4×10^-3. Below this concentration the theory becomes more widely discrepant from the experiment and MVA worse than CRTA at lower concentrations. At very low concentrations (〜10^-4), where the relevant spectral density falls into its tail and the previous result is invalid, T_1 is treated on the basis of CRTA, where the spin-rotation relaxation rate is much faster than the cross relaxation rate for o-H_2 pair lying inside the energy conservation layer. The configuration average is taken by assuming the mean thickness of the energy conservation layer which is estimated approximately from the width of the effective spectral density function propoitional to x_0^<5/3>, resulting T_1∝x_0^<-11/3> in agreement with experiments. It is also shown that the detailed treatment gives almost the same result with some improvement.
- 理論物理学刊行会の論文
- 1975-09-25
著者
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Nakamura Tuto
Faculty Of Engineering Science Osaka University
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FUJIO Motoya
Department of Material Physics, Faculty of Engineering Science, Osaka University
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Fujio Motoya
Faculty Of Engineering Science Osaka Univirsity
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Fujio Motoya
Faculty Of Engineering Science Osaka University
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Nakamura Tuto
Faculty Of Engineering Science Osaka Univirsity
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FUJIO Motoya
Department of Material Physics, Faculty of Engineering Science Osaka University
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FUJIO Motoya
Faculty of Engineering Science, Osaka Univirsity
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