Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid-State NMR Spectroscopy.
Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid-State NMR Spectroscopy.
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DOI：
10.1002/cphc.201601003
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发表时间：
2017-02-17
期刊：
影响因子：
--
通讯作者：
Hodgkinson P
中科院分区：
文献类型：
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作者：
Frantsuzov I;Vasa SK;Ernst M;Brown SP;Zorin V;Kentgens AP;Hodgkinson P
通过自旋回波下核磁化衰减的时间常数，探讨了影响~1H异核去耦合序列用于有机固体魔角旋转(MAS)核磁共振谱性能的因素。通过在包括非常高的磁场和非常高的射频章动速率在内的广泛的实验条件下使用共同的协议，观察到解耦性能随着磁场的增加而一致地下降。射频场的不均匀对数值有很大的影响，不同线圈几何形状的探头之间观察到的差异约为20 %。不断增加的射频章动速率显著提高了相对于射频偏移的稳健性，但由于射频瞬变，相位调制序列的性能在微线圈中可以实现的非常高的章动速率下性能下降。所获得的见解有助于更好地理解在不同条件下限制去耦合性能的因素，并且观察值(通常超过以前的文献值)为涉及自旋磁化重聚焦的实验提供了参考点，例如2D关联谱和测量小的自旋耦合。
Factors affecting the performance of 1H heteronuclear decoupling sequences for magic‐angle spinning (MAS) NMR spectroscopy of organic solids are explored, as observed by time constants for the decay of nuclear magnetisation under a spin‐echo ( ). By using a common protocol over a wide range of experimental conditions, including very high magnetic fields and very high radio‐frequency (RF) nutation rates, decoupling performance is observed to degrade consistently with increasing magnetic field. Inhomogeneity of the RF field is found to have a significant impact on values, with differences of about 20 % observed between probes with different coil geometries. Increasing RF nutation rates dramatically improve robustness with respect to RF offset, but the performance of phase‐modulated sequences degrades at the very high nutation rates achievable in microcoils as a result of RF transients. The insights gained provide better understanding of the factors limiting decoupling performance under different conditions, and the high values of observed (which generally exceed previous literature values) provide reference points for experiments involving spin magnetisation refocussing, such as 2D correlation spectra and measuring small spin couplings.