Edén Mattias, Lo Andy Y H
Physical Chemistry Division, Stockholm University, Stockholm, Sweden.
J Magn Reson. 2009 Oct;200(2):267-79. doi: 10.1016/j.jmr.2009.07.007. Epub 2009 Jul 12.
Using average Hamiltonian (AH) theory, we analyze recently introduced homonuclear dipolar recoupling pulse sequences for exciting central-transition double-quantum coherences (2QC) between half-integer spin quadrupolar nuclei undergoing magic-angle-spinning. Several previously observed differences among the recoupling schemes concerning their compensation to resonance offsets and radio-frequency (rf) inhomogeneity may qualitatively be rationalized by an AH analysis up to third perturbation order, despite its omission of first-order quadrupolar interactions. General aspects of the engineering of 2Q-recoupling pulse sequences applicable to half-integer spins are discussed, emphasizing the improvements offered from a diversity of supercycles providing enhanced suppression of undesirable AH cross-terms between resonance offsets and rf amplitude errors.
利用平均哈密顿量（AH）理论，我们分析了最近引入的用于激发处于魔角旋转的半整数自旋四极核之间中心跃迁双量子相干（2QC）的同核偶极重耦合脉冲序列。尽管AH分析忽略了一阶四极相互作用，但对于重耦合方案之间先前观察到的在补偿共振偏移和射频（rf）不均匀性方面的若干差异，通过直至三阶微扰阶次的AH分析可进行定性解释。讨论了适用于半整数自旋的2Q重耦合脉冲序列设计的一般方面，强调了多种超循环所带来的改进，这些超循环可增强对共振偏移和rf幅度误差之间不良AH交叉项的抑制。
