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

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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