Dynamics of Spectroscopic Relaxation Processes in Noise Fields
Project/Area Number  02640292 
Research Category 
GrantinAid for Scientific Research (C).

Research Field 
物理学一般

Research Institution  College of Liberal Arts, Kobe University 
Principal Investigator 
FUKUDA Yukio Kobe Univ., Col. of Liberal Arts, Ass. Prof., 教養部, 助教授 (40025482)

CoInvestigator(Kenkyūbuntansha) 
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)
KUNITOMO Masakazu Kobe Univ., Col. of Liberal Arts, Professor, 教養部, 教授 (40031348)
KOHMOTO Tosiro Kobe Univ., Col. of Liberal Arts, Lecturer, 教養部, 講師 (70192573)

Project Fiscal Year 
1990 – 1991

Project Status 
Completed(Fiscal Year 1991)

Budget Amount *help 
¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1991 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1990 : ¥2,000,000 (Direct Cost : ¥2,000,000)

Keywords  Noise Field / Spectroscopy / Relaxation Process / TwoState Noise / Antiferromagnet CsCoCl_3 / GaussianMarkov Noise / Stochastic Theory / 雑音場 / 分光学 / 緩和過程 / 2状態雑音 / 反強磁性体 / ガウス・マルコフ雑音 / ストカスティック理論 / レザ分光 / 磁気共鳴 / 位相緩和 
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 pulsedNMR 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 welldefined 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 twostate 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_2^21 or >1. Secondly, we applied the above result to the phase relaxation of the Cs NMR observed in Isinglike 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 GaussianMarkov noises and already obtained some new results. A paper reporting on twostate 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

Report
(4results)
Research Output
(6results)