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首页> 外文期刊>The Journal of Chemical Physics >A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance
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A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance

机译：固态MAS NMR中自旋解耦描述的广义理论框架：偏移对解耦性能的影响

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摘要

We present a generalized theoretical framework that allows the approximate but rapid analysis of residual couplings of arbitrary decoupling sequences in solid-state NMR under magic-angle spinning conditions. It is a generalization of the tri-modal Floquet analysis of TPPM decoupling [Scholz et al., J. Chem. Phys. 130, 114510 (2009)] where three characteristic frequencies are used to describe the pulse sequence. Such an approach can be used to describe arbitrary periodic decoupling sequences that differ only in the magnitude of the Fourier coefficients of the interaction-frame transformation. It allows a similar to 100 times faster calculation of second-order residual couplings as a function of pulse sequence parameters than full spin-dynamics simulations. By comparing the theoretical calculations with full numerical simulations, we show the potential of the new approach to examine the performance of decoupling sequences. We exemplify the usefulness of this framework by analyzing the performance of commonly used high-power decoupling sequences and low-power decoupling sequences such as amplitude-modulated XiX (AM-XiX) and its super-cycled variant SC-AM-XiX. In addition, the effect of chemical-shift offset is examined for both high-and low-power decoupling sequences. The results show that the cross-terms between the dipolar couplings are the main contributions to the line broadening when offset is present. We also show that the SC-AM-XIX shows a better offset compensation. Published by AIP Publishing.
机译：我们提供了一个广义的理论框架，该框架允许在魔角旋转条件下对固态NMR中任意解偶联序列的残基偶联进行近似但快速的分析。它是TPPM去耦的三峰Floquet分析的概括[Scholz等，化学学报，2003年。物理130，114510（2009）]，其中三个特征频率用于描述脉冲序列。这种方法可用于描述仅在交互帧变换的傅立叶系数的大小上不同的任意周期性解耦序列。与完整的自旋动力学仿真相比，它可根据脉冲序列参数将二阶残余耦合的计算速度提高约100倍。通过将理论计算与完整的数值模拟进行比较，我们展示了这种新方法检查去耦序列性能的潜力。我们通过分析常用的高功率去耦序列和低功率去耦序列（例如调幅XiX（AM-XiX）及其超循环变体SC-AM-XiX）的性能来例证此框架的有用性。此外，还针对高功率和低功率去耦序列检查了化学位移偏移的影响。结果表明，当存在偏移时，偶极耦合之间的交叉项是线扩展的主要贡献。我们还表明，SC-AM-XIX显示出更好的失调补偿。由AIP Publishing发布。

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