Nuclear magnetic resonance signal dynamics of liquids in the presence of distant dipolar fields, revisited.
Nuclear magnetic resonance signal dynamics of liquids in the presence of distant dipolar fields, revisited.
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DOI：
10.1063/1.3116107
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
W. Barros;D. Gochberg;J. Gore
中科院分区：
文献类型：
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作者：
W. Barros;D. Gochberg;J. Gore
在长程偶极相互作用下的核磁共振磁化动力学的描述，这是基于近似解的布洛赫-托里方程，包括一个遥远的偶极场的影响，已被重新审视。新的实验表明，近似解析解具有更广泛的有效性以及对脉冲序列参数的依赖性，这些参数似乎被忽视了。为了解释这些实验结果，我们开发了一种新的方法，包括通过迭代形式主义的扩散和远偶极场的贡献被视为积分算子纳入布洛赫-托里方程的计算磁化。该解决方案可以组织为一个扰动系列，从而访问高阶项允许一个更好的边界上的有效性制度的分析一阶近似。最后，该方法合法化的使用简单的分析一阶近似在要求不高的实验条件下，它预测新的脉冲序列参数的依赖性的有效性范围内，并澄清在以前的计算中的弱点。
The description of the nuclear magnetic resonance magnetization dynamics in the presence of long-range dipolar interactions, which is based upon approximate solutions of Bloch-Torrey equations including the effect of a distant dipolar field, has been revisited. New experiments show that approximate analytic solutions have a broader regime of validity as well as dependencies on pulse-sequence parameters that seem to have been overlooked. In order to explain these experimental results, we developed a new method consisting of calculating the magnetization via an iterative formalism where both diffusion and distant dipolar field contributions are treated as integral operators incorporated into the Bloch-Torrey equations. The solution can be organized as a perturbative series, whereby access to higher order terms allows one to set better boundaries on validity regimes for analytic first-order approximations. Finally, the method legitimizes the use of simple analytic first-order approximations under less demanding experimental conditions, it predicts new pulse-sequence parameter dependencies for the range of validity, and clarifies weak points in previous calculations.