Through-space heteronuclear correlation (D-HETCOR) experiments based on heteronuclear multiple-quantum correlation (D-HMQC) and refocused insensitive nuclei enhanced by polarization transfer (D-RINEPT) sequences have been proven to be useful approaches for the detection of the spatial proximity between half-integer quadrupolar nuclei in solids under magic-angle spinning (MAS) conditions. The corresponding pulse sequences employ coherence transfers mediated by heteronuclear dipolar interactions, which are reintroduced under MAS by radiofrequency irradiation of only one of the two correlated nuclei. We investigate herein using numerical simulations of spin dynamics and solid-state NMR experiments on magnesium aluminoborate glass how the choice of the channel to which the heteronuclear dipolar recoupling is applied affects the transfer efficiency of D-HMQC and D-RINEPT sequences between ¹¹B and ²⁷Al nuclei. Experimental results show that maximum transfer efficiency is achieved when the recoupling scheme is applied to the channel, for which the spin magnetization is parallel to the B₀ axis in average.

中文翻译：

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通过空间 11B-27Al 相关性：重新耦合通道的影响

通空间异核相关（d基于异核多量子相关-HETCOR）实验（d -HMQC）和重新聚焦不敏感核极化转移（增强d-RINEPT) 序列已被证明是在魔角旋转 (MAS) 条件下检测固体中半整数四极核之间空间接近度的有用方法。相应的脉冲序列采用由异核偶极相互作用介导的相干转移，这些转移在 MAS 下通过仅对两个相关核中的一个进行射频照射而重新引入。我们在本文中使用自旋动力学的数值模拟和铝硼酸镁玻璃的固态 NMR 实验研究了应用异核偶极再耦合的通道的选择如何影响D- HMQC 和D- RINEPT 序列在¹¹ B 和²⁷铝核。实验结果表明，当再耦合方案应用于自旋磁化平均平行于B ₀轴的通道时，实现了最大的传输效率。