Dynamics of Spectroscopic Relaxation Processes in Noise Fields

本研究的目的是重新考虑相干谱弛豫过程的基本概念，建立一个全面的描述谱弛豫过程的方法。自旋回波等）质子在水中的自旋进行了检测。在利用噪声源如噪声二极管进行了初步实验后，我们开发了计算机程序，用于产生各种定义明确的噪声。然后通过D/A转换器和电流放大器，在平行于静磁场的方向上用线圈施加噪声。首先，我们研究了最简单也是最基本的噪声类型之一--双态噪声的情况，得到了一个值得注意的结果。我们考虑了一个马尔可夫过程，其中磁场随机地跳回到两个状态之间， ...更多信息 不同的寿命τ_1和τ_2。在这种情况下，我们可以解析地获得相干瞬态的衰减函数的表达式。特别是当τ_1>> τ_2时，我们理论上得到了一个指数衰减，其时间常数T_2（相位弛豫时间）为1/T_2=（1/τ_1）γ ^2 Δ H^2 τ_2^2/（1+ γ ^2 Δ H^2 τ_2^2），其中γ H是两个态之间的磁场差。该公式得到了实验验证。传统的随机理论仅在γ ^2 Δ H^2 τ ^2 <<1的极限下才能得到相同的结果，而在γ ^2 Δ H^2 τ ^2 -1或> 1的极限下则不能得到相同的结果。其次，我们将上述结果应用于类Ising反铁磁体CsCoCl_3中Cs NMR的相位弛豫，阐明了Co离子磁自旋系统的动力学过程。最后，我们一直在研究高斯-马尔可夫噪声下的相位弛豫过程，并取得了一些新的结果，已经提交了一篇关于两态噪声的论文，另一篇关于CsCoCl_3的论文即将提交。关于高斯噪声的结果也将在不久的将来报道。少

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 … More 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 by1/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