1991 Fiscal Year Final Research Report Summary
Dynamics of Spectroscopic Relaxation Processes in Noise Fields
| Project/Area Number |
02640292
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理学一般
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| Research Institution | College of Liberal Arts, Kobe University |
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Principal Investigator |
FUKUDA Yukio Kobe Univ., Col. of Liberal Arts, Ass. Prof., 教養部, 助教授 (40025482)
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| Co-Investigator(Kenkyū-buntansha) |
EBINA Kuniyosi Kobe Univ., Col. of Liberal Arts, Lecturer, 教養部, 講師 (50151999)
KABURAGI Makoto Kobe Univ., Col. of Liberal Arts, Professor, 教養部, 教授 (40093504)
KOHMOTO Tosiro Kobe Univ., Col. of Liberal Arts, Lecturer, 教養部, 講師 (70192573)
KUNITOMO Masakazu Kobe Univ., Col. of Liberal Arts, Professor, 教養部, 教授 (40031348)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Noise Field / Spectroscopy / Relaxation Process / Two-State Noise / Antiferromagnet CsCoCl_3 / Gaussian-Markov Noise / Stochastic Theory |
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| Research Abstract |
The aim of this research project is to reconsider the fundamental concepts of relaxation processes in the coherent spectroscopy and to establish a comprehensive procedure for describing the spectroscopic relaxation processes.
We made an pulsed-NMR experiment in which NMR coherent transient phenomena (free induction decay. spin echo, etc.) of proton spins in water were examined. After making some preliminary experiments by using noise sources like a noise diode, we developed computer programs for generating variety of well-defined noises. Then the noise is applied with a coil in the direction parallel to the static magnetic field through a D/A converter and a current amplifier. The phase relaxation time T_2 was measured and analyzed.
Firstly, we studied the case of two-state noise, one of the simplest and the most fundamental type of noises, and obtained a noticeable result. We considered a Markov process in which the magnetic field randomly jumps back and force between two states with di
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fferent lifetimes tau_1 and tau_2. In this case, we could obtain analytically an expression of the decay function for the coherent transients. Especially for tau_1>>tau_2, we theoretically obtained a exponential decay with a time constant T_2 (the phase relaxation time) given by
1/T_2=(1/tau_1)gamma^2deltaH^2tau_2^2/(1+gamma^2deltaH^2tau_2^2) where gammaH is the difference of the magnetic field between the two states. This formula was confirmed by the experiment. The conventional stochastic theory predicts the same result only in the limit of gamma^2deltaH^2tau_2^2<<1 and it can not be not used for gamma^2deltaH^2tau_2^2-1 or >1.
Secondly, we applied the above result to the phase relaxation of the Cs NMR observed in Ising-like antiferromagnet CsCoCl_3 and elucidated the dynamical process of the magnetic spin system of Co ions. This result is worth noticing in the meaning that it shows the usefulness of the measurement of the NMR phase relaxation in the study of magnetic materials.
Lastly, we have been studying phase relaxation processes under Gaussian-Markov noises and already obtained some new results.
A paper reporting on two-state noises has been submitted and another on CsCoCl_3 is about to be submitted. The result on Gaussian noises will also be reported before long. Less
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Research Products
(4 results)
