Low‐load rotor‐synchronised Hahn‐echo pulse train (RS‐HEPT) 1H decoupling in solid‐state NMR: factors affecting MAS spin‐echo dephasing times
Low‐load rotor‐synchronised Hahn‐echo pulse train (RS‐HEPT) 1H decoupling in solid‐state NMR: factors affecting MAS spin‐echo dephasing times
复制标题
固态核磁共振中的低负载转子同步哈恩回波脉冲串（RS-HEPT）1H解耦：影响MAS自旋回波相移时间的因素
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
S. Brown
中科院分区：
文献类型：
--
作者：
J. Griffin;C. Tripon;A. Samoson;C. Filip;S. Brown
利用转子同步Hahn回波脉冲序列（RS - HEPT）低负载1H去耦，对自旋回波MAS NMR中的横向减相次数T2 '进行了评估。实验分别在300和600 MHz的频率下对13CH标记的L -丙氨酸和15nhh （δ）标记的L -组氨酸·HCl·H2O进行了实验，并对代表L -丙氨酸中13CH碳晶体结构环境的十自旋系统进行了SPINEVOLUTION模拟。对于30 kHz MAS和300 MHz ν1(1H) = 100 kHz， 13CH标记的L -丙氨酸的RS - HEPT T2 ‘值为17±1 ms，是XiX T2 ’值33±2 ms的约50%。当RS - HEPT π脉冲的相对相位Δϕ = φ - φ在40°和60°之间时，RS - HEPT去耦效果最佳。在600 MHz和30 kHz的频率下，用13CH标记的L -丙氨酸进行实验，最佳的RS - HEPT (ν1(1H) = 100 kHz) T2′值比低功率连续应用ν1(1H)≤40 kHz的序列所观察到的值长3倍，即对应于相同的探针平均功耗。随着MAS频率的增加，观察到RS - HEPT 1H解耦的显着改善：在55.6 kHz MAS下，13CH标记的L -丙氨酸的最佳RS - HEPT T2 '值为34±5 ms。与30 kHz MAS相比，在55.6 kHz MAS下也观察到RS - HEPT宽带性能有很大改善。版权所有©2007 John Wiley & Sons， Ltd
Transverse dephasing times T2′ in spin‐echo MAS NMR using rotor‐synchronised Hahn‐echo pulse‐train (RS‐HEPT) low‐load 1H decoupling are evaluated. Experiments were performed at 300 and 600 MHz for 13CH‐labelled L‐alanine and 15NH(δ)‐labelled L‐histidine·HCl·H2O, together with SPINEVOLUTION simulations for a ten‐spin system representing the crystal structure environment of the 13CH carbon in L‐alanine. For 30 kHz MAS and ν1(1H) = 100 kHz at 300 MHz, a RS‐HEPT T2′ value of 17 ± 1 ms was obtained for 13CH‐labelled L‐alanine which is ∼50% of the XiX T2′ value of 33 ± 2 ms. Optimum RS‐HEPT decoupling performance is observed for a relative phase of alternate RS‐HEPT π–pulses, Δϕ = ϕ′− ϕ, between 40 and 60° . For experiments at 600 MHz and 30 kHz MAS with 13CH‐labelled L‐alanine, the best RS‐HEPT (ν1(1H) = 100 kHz) T2′ value was 3 times longer than that observed for low‐power continuously applied sequences with ν1(1H) ⩽40 kHz, i.e. corresponding to the same average power dissipated in the probe. A marked improvement in RS‐HEPT 1H decoupling is observed for increasing MAS frequency: at 55.6 kHz MAS, a best RS‐HEPT T2′ value of 34 ± 5 ms was recorded for 13CH‐labelled L‐alanine. Much improved RS‐HEPT broadband performance was also observed at 55.6 kHz MAS as compared to 30 kHz MAS. Copyright © 2007 John Wiley & Sons, Ltd.