Research of high-resolutions NMR measurements for solid 14N spins by Dynamic Sample spinning NMR

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We tried to increase the spinning frequency of a rotor in a Dynamic Angle Spinning (DAS) NMR probe in 2003. To that end, we made some NMR rotors with different caps, and drove the DAS system using the rotors. The maximum rotor spinning frequency was, however, about 6kHz; we could not make the DAS system that can switch the spinning axis at the spinning frequency of more than 10kHz. We consequently adopted a different strategy in order to attain the objective of this study.First, we theoretically studied the indirect detection of overtone NMR for ^<23>Na nuclei in polycrystalline solids. As a result, we obtained the following findings:when the ^<23>Na overtone irradiation is performed using different irradiation frequencies, if we plot the central transition intensities against the irradiation frequencies, we can obtain a high-resolution NMR spectrum for ^<23>Na nuclei in solids.14N nuclei in polycrystalline solids also have two normal transitions and one overtone transition. Thus the above indirect detection method is applicable to the 14N spins in solids; the indirect detection method should produce high-resolution NMR spectra for 14N spins.Now, we are making a double resonance MAS probe which has two channels corresponding to a 14N resonance frequency and a 14N overtone frequency.