Unconventional diffusion behaviors of intermolecular multiple-quantum coherences in nuclear magnetic resonance
Unconventional diffusion behaviors of intermolecular multiple-quantum coherences in nuclear magnetic resonance
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DOI：
10.1063/1.1350919
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发表时间：
2001-04
影响因子：
4.4
通讯作者：
Zhong Chen;J. Zhong
中科院分区：
文献类型：
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作者：
Zhong Chen;J. Zhong
到目前为止，分子间多量子相干(MQC)和退磁场模型都已经导致了使用银纹化和相似序列对高极化系统中的核磁共振信号进行完全定量的预测。本文通过对表观相干级数n的表观MQC扩散速率Dnapp的测量，研究了分子间MQC和退磁场处理之间的等价性。从理论和实验上分析了一些物理效应。这些效应包括分子扩散、偶极关联距离的变化、辐射衰减、非均匀展宽和自旋弛豫，所有这些都可能改变核磁共振信号。为了准确测量和表征Dnapp的演化过程，设计了两个双脉冲CRAZED序列的变种，其中信号衰减几乎完全由扩散加权引起。表观扩散速率是从最小二乘拟合的一系列1H…
To date, both the intermolecular multiple-quantum coherence (MQC) and demagnetizing field models have led to fully quantitative predictions of NMR signals in a highly polarized system using the CRAZED and similar sequences. In this paper, measurements of apparent MQC diffusion rates, Dnapp, for a specific apparent coherence order, n, were used to investigate the equivalent between the intermolecular MQC and demagnetizing field treatments. A number of physical effects were analyzed both theoretically and experimentally. These effects include molecular diffusion, variation in dipolar correlation distance, radiation damping, inhomogeneous broadening, and spin relaxation, all of which may alter the NMR signal. Two variations of a two-pulse CRAZED sequence, where the signal attenuation is almost entirely caused by the diffusion weighting, were designed to accurately measure and characterize Dnapp during the evolution period. Apparent diffusion rates were extracted from a least-squares fitting of a series of 1H...