Generalised magnetisation-to-singlet-order transfer in nuclear magnetic resonance
Generalised magnetisation-to-singlet-order transfer in nuclear magnetic resonance
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DOI：
10.1039/d0cp00935k
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发表时间：
2020-05-07
影响因子：
3.3
通讯作者：
Levitt, Malcolm H.
中科院分区：
文献类型：
--
作者：
Bengs, Christian;Sabba, Mohamed;Levitt, Malcolm H.
已经描述了各种脉冲序列，用于将核自旋磁化转化为核自旋-1/2对的长寿命单重态有序。现有序列在两种极端参数条件下运行良好。磁化到单重态（M2S）脉冲序列在接近等效的极限下实现了核自旋磁化到单重态的鲁棒转换，这意味着两个自旋的化学位移频率的差异远小于自旋-自旋耦合。其他脉冲序列工作在强不等态，其中位移差比自旋-自旋耦合大得多。然而，这两组脉冲序列在中间区域失效，其中化学位移差和自旋-自旋耦合的幅度大致相等。我们描述了M2S的一个广义版本，称为gM2S，它实现了自旋系统的鲁棒单重态有序激发，范围从接近等效极限到中间状态。这弥补了现有脉冲序列留下的一个重要空白。gM2S序列的效率在接近等效和中间状态的情况下得到了数值和实验证明。
A variety of pulse sequences have been described for converting nuclear spin magnetisation into long-lived singlet order for nuclear spin-1/2 pairs. Existing sequences operate well in two extreme parameter regimes. The magnetisation-to-singlet (M2S) pulse sequence performs a robust conversion of nuclear spin magnetisation into singlet order in the near-equivalent limit, meaning that the difference in chemical shift frequencies of the two spins is much smaller than the spin-spin coupling. Other pulse sequences operate in the strong-inequivalence regime, where the shift difference is much larger than the spin-spin coupling. However both sets of pulse sequences fail in the intermediate regime, where the chemical shift difference and the spin-spin coupling are roughly equal in magnitude. We describe a generalised version of M2S, called gM2S, which achieves robust singlet order excitation for spin systems ranging from the near-equivalence limit well into the intermediate regime. This closes an important gap left by existing pulse sequences. The efficiency of the gM2S sequence is demonstrated numerically and experimentally for near-equivalent and intermediate-regime cases.