Indirect spin-spin coupling in multiple-quantum magic-angle-spinning NMR spectra of quadrupolar nuclei.
Indirect spin-spin coupling in multiple-quantum magic-angle-spinning NMR spectra of quadrupolar nuclei.
复制标题
四极核多量子魔角自旋核磁共振谱中的间接自旋耦合。
DOI：
10.1006/jmre.1996.1042
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Griffin,RG
中科院分区：
文献类型：
--
作者：
Wu,G;Kroeker,S;Wasylishen,RE;Griffin,RG
a （S, m）的选择值如表1所示。这表明存在1 J （11B, 31P）。显然，从表1中可以看出，在11B MAS光谱中，JMQ可以是四极增宽的两倍以上，这使得JMQ比J大。例如，对1j （11B, 31P）的异核J观测很困难。而（PhO） 3P-BH3 （S Å 32）核的各向同性MQMAS谱为7.4,11B等位会引起2.125J的分裂。MQMAS T（图2）的这种独特性质除了去除二阶四赫兹外，还显示了180{10方法的分裂双重态，因此根据极性展宽产生1 J （11B, 31P） Å 85 {5 Hz，进一步增强了其检测相关Eq.[1]的能力。固体材料中各向同性J耦合峰的线宽都很小。从表1中可以看出，比例因子取决于为MQMAS实验选择的MQ一致性。更具体地说，最大的分裂是在最高阶MQ相干2S中发现的，而对于低阶MQ相干，JMQ小于J，除了S Å 92系统中的7Q相干。这种异常大的JMQ也存在于S ú 9的四极系统中
Selected values of a (S, m) are given in Table 1. It is interestsuggest the presence of 1 J (11B, 31P). Clearly, second-order ing to note in Table 1 that JMQ can be more than twice as quadrupole broadening in the 11B MAS spectrum makes the large as J. For instance, the presence of a heteronuclear J observation of 1 J (11B, 31P) difficult. In contrast, the 11B isowill cause a splitting of 2.125J in isotropic 3Q MAS spectra tropic MQMAS spectrum of (PhO) 3P–BH3 observed at 7.4 for S Å 3 2 nuclei. This unique property of the MQMAS T (Fig. 2) exhibits a doublet with a splitting of 180 {10 method, in addition to the removal of second-order quadru-Hz, therefore yielding 1 J (11B, 31P) Å 85 {5 Hz according polar broadening, further enhances its ability to detect relato Eq.[1]. The linewidth of the peaks in the isotropic 11B tively small J couplings in solid materials. It can be seen in Table 1 that the scaling factor depends upon the MQ coherence chosen for the MQMAS experiment. More specifically, the largest splitting is found for the highest order MQ coherence, 2S, whereas for lower order MQ coherences, JMQ is smaller than J, except for the 7Q coherence in S Å 92 systems. Such anomalously large JMQ also exists in quadrupolar systems with S ú 9