高速魔角旋转下基于组合π脉冲的射频驱动重耦同核双量子固体NMR相关实验研究  

Study of Radio Frequency-driven Recoupling Homonuclear Doublequantum Solid-state NMR Correlation Experiments Based on Com⁃positeπPulses at High Magic-angle-spinning Speed

作　　者：宋佩君 易迎彦[1] 王秀梅 张正逢 SONG Pei-jun;YI Ying-yan;WANG Xiu-mei;ZHANG Zheng-feng(School of Science,Wuhan University of Technology,Wuhan 430070,China;Bruker(Beijing)Scientific Technology Co.Ltd.,Beijing 100192,China;Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,China)

机构地区：[1]武汉理工大学理学院,湖北武汉430070 [2]布鲁克(北京)科技有限公司,北京100192 [3]中国科学院精密测量科学与技术创新研究院,湖北武汉430071

出　　处：《分析测试学报》2024年第6期898-904,共7页Journal of Instrumental Analysis

基　　金：国家自然科学基金(22074153)。

摘　　要：该文提出了一种改进固体核磁共振(NMR)实验中射频驱动重耦(RFDR)序列的方法。以组合π脉冲替代传统的单一矩形π脉冲作为RFDR序列的基本构成单元,并选择若干个适用于高速魔角旋转条件的组合π脉冲,在RFDR双量子实验中进行全面研究,通过数值模拟分析了影响RFDR双量子实验性能的两个关键因素——共振偏置和射频场不均匀性,并根据模拟结果确定了性能最优的组合π脉冲。结合六氟硅酸钠和L-组氨酸的一维和二维^(19)F或1H固体NMR实验,验证了在高速魔角旋转条件下选择适当的组合π脉冲的RFDR序列的优势。该方法不仅能确保较高的同核双量子激发效率,还能提高激发带宽,并且对射频场不均匀性更加不敏感。稳定高效的RFDR同核双量子相关实验为采用固体NMR分析强自旋耦合体系的核间相互作用提供了重要的技术支持。This study presents a way to improve the performance of radio frequency-driven recoupling(RFDR)sequences in solid-state nuclear magnetic resonance(NMR)spectroscopy.Traditional RF⁃DR sequences typically employ single rectangularπpulses,which may prove to be inefficient,espe⁃cially in experiments under high-speed magic angle spinning(MAS)conditions that have become more popular in recent years.To address this issue,we proposed using compositeπpulses to replace the traditional single rectangularπpulses in RFDR sequences.The updated RFDR sequence enables more precise control over nuclei spins and provides better performance in double-quantum(DQ)ex⁃periments compared to the traditional module based on single rectangularπpulses.Our focus was specifically on the investigation of multiple compositeπpulses,which are suitable for use under high-speed MAS conditions.To evaluate the efficacy of DQ excitation of these compositeπpulses within the RFDR sequence,we conducted a comprehensive investigation by using numerical simula⁃tions and experiments.Initially,we analyzed the impact of two critical factors on the performance of RFDR in DQ excitation experiments:resonance offset and radio frequency(RF)field inhomogene⁃ity.The resonance offset signifies the difference between the nuclei Larmor frequency and the fre⁃quency of the applied RF field,while the RF field inhomogeneity describes the variations in RF field strength throughout the sample.Through a comparative analysis of outcomes from a single rectangularπpulse and multiple compositeπpulses,we identified a promising RFDR sequence based on a com⁃positeπpulse.Subsequently,this optimized RFDR sequence was integrated into DQ experiments and tested via one-dimensional(1D)and two-dimensional(2D)experiments on^(19)F for sodium hexaflu⁃orosilicate or 1H for L-histidine.The results confirmed that,under high-speed MAS conditions,the RFDR sequence with appropriate compositeπpulses can offer several advantages over the traditional RFDR with single rectangular

关 键 词：固体核磁共振 魔角旋转 组合脉冲 偶极重耦 双量子-单量子相关 射频驱动重耦(RFDR) 

分 类 号：O615.4[理学—无机化学] O482.53[理学—化学]