Development of New Methods for NMR of Spin*1 in Solids

我们研究了几种NMR方法来观察自旋为 *1的核的NMR。首先，我们修改了我们的商业NMR仪器，将一个新的多功能脉冲编程器和快速A/D转换器。这些改进使观察到自旋为1的核的宽线形NMR信号成为可能。其次，我们观察到^ N的泛频NMR<14>，在<1>泛频方法中，^N的大的一级四极相互作用被消除，在泛频方法中，^ N的“泛频”跃迁被观察<14>到。剩余的谱线展宽主要来自于二阶四极子分裂。研究了样品自旋对固体中自旋为1的四极核“泛音”NMR的影响，探讨了从“泛音”谱中消除二级四极展宽的可能性。当自旋角为60-70 °时，二阶四极展宽的平均值较好，灵敏度较高。当魔角为54.7 °时，二阶四极展宽的平均值较窄。 ...更多信息 二阶四极展宽的单峰。由于魔角自旋平均了偶极-偶极和化学位移相互作用等各向异性，因此魔角自旋可以用于具有较大化学位移各向异性和偶极-偶极相互作用的样品。此外，“泛音”NMR方法被用于确定单晶中^ N核的四极耦合张量<14>。本文还发展了单晶泛频核磁共振分析的理论基础。结果表明，尽管泛音法在精确测定四极耦合常数方面不太理想，但仍具有一定的优越性。它比传统的^ N单量子方法需要更少的硬件要求<14>;人们可以<14>在一个频谱中观察到所有^ N个信号。这使得我们能够在^ N共振之间进行二维交换NMR<14>。很容易观察到所有^ N核的四极耦合常数随温度的变化<14>。少

We examined several NMR approaches to observe NMR of nuclei with spin*1. Firstly, we modified our commercial NMR apparatus to incorporate a new versatile pulse programmer and a fast A/D converter. The modifications makes it possible to observe NMR signal with wide line-shape of spin*1 nuclei. Secondly, we observed the overtone NMR of ^<14>N in which the "overtone" transition (1 <1> -1) is observed.In the overtone approach, the large first-order quadrupole interaction is eliminated for ^<14>N. The remaining line-broadening mainly comes from the second-order quadrupole splitting. Effects of sample spinning on the "overtone" NMR of quadrupole nuclei with spin=1 in the solid are investigated to exploit a possibility for removing the second-order quadrupole broadening from the "overtone" spectra. A good averaging of the second-order quadrupole broadening and a high sensitivity are achieved at spinning angles of 60-70ﾟ It is also shown that the magic angle (54.7ﾟ) produces a rather narrow si … More ngle-peak for the second-order quadrupole broadening. Since the magic-angle spinning averages other anisotropies such as dipole-dipole and chemical shift interactions, it is concluded that the magic angle spinning can be used for samples with a large chemical shift anisotropy and/or dipole-dipole interactions.Furthermore, the "overtone" NMR approach was used to determine a quadrupole coupling tensor of the ^<14>N nucleus in a single crystal. The theoretical basis of analysis of overtone NMR for a single crystal is also developed. It was found that the present overtone approach has some advantages, although it is not very promising for the accurate determination of quadrupole coupling constant. It demands less hardware requirement than the conventional ^<14>N single quantum approach ; one can observe all of ^<14>N signals in one spectrum. This allows us to conduct the two-dimensional exchange NMR among ^<14>N resonances. It is easy to observe the temperature dependence of quadrupole coupling constant of all ^<14>N nuclei. Less