Spherical rotors are a new paradigm in magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR). The simple geometry makes smaller diameter spheres and their utilization within narrow-bore NMR probes feasible. Here we report a 68 kHz spinning frequency of 2 mm diameter spheres using helium spinning gas outside the magnet and demonstrate the use of KMnO₄ to adjust the magic angle at a spinning frequency of 59.3 kHz for MAS NMR. We observe third-order spinning sidebands in the ⁵⁵Mn spectrum clearly showing the MAS frequency of 59.3 kHz, with KBr showing nearly no first-order spinning sidebands at a similar frequency. The spinning stability was ±0.5% during data acquisition without spinning regulation. To address concerns about the low NMR filling factor of MAS spheres, we employ a modified stator and a smaller coil and achieve three times higher NMR sensitivity then our previous coil geometries for MAS spheres. Advanced coil and rotor fabrication technologies are expected to further increase the spinning frequency and NMR sensitivity of MAS spheres.

球形转子是魔角旋转 (MAS) 固态核磁共振 (NMR) 的新范例。简单的几何形状使较小直径的球体及其在窄孔 NMR 探针中的应用变得可行。在这里，我们报告了 68 kHz 旋转频率的 2 mm 直径球体，使用磁体外部的氦气旋转气体，并演示了使用 KMnO ₄来调整 MAS NMR 的旋转频率为 59.3 kHz 的魔角。我们观察到^{55 度中}的三阶自旋边带Mn 谱清楚地显示了 59.3 kHz 的 MAS 频率，KBr 在类似频率下几乎没有显示出一阶自旋边带。在没有纺纱调节的情况下，在数据采集期间纺纱稳定性为±0.5%。为了解决对 MAS 球体的 NMR 填充系数低的担忧，我们采用了改进的定子和更小的线圈，实现了比我们之前用于 MAS 球体的线圈几何结构高三倍的 NMR 灵敏度。先进的线圈和转子制造技术有望进一步提高 MAS 球体的自旋频率和 NMR 灵敏度。