Precise alignment of the sample's spinning axis is vital for many magic angle spinning solid state NMR experiments. Spherical rotors are a new paradigm for magic angle spinning NMR, having been demonstrated to spin stably with little risk of rotor crash, but like cylindrical rotors, they have previously only utilized a mechanical adjustment method to set the sample's rotation axis to the magic angle. Here we show that by using a second gas aperture within the stator, a spherical rotor's axis of rotation may be precisely pitched about the magic angle without mechanical adjustment or motion of the stator. The ²H MAS sideband lineshape of the carboxylic acid deuteron resonance in d₄-malonic acid is used as a measure of the rotor's absolute deviation above or below the magic angle by comparing the experimental data to simulated lineshapes. We observe a linear, monotonic relationship between the angle adjustment gas flow rate and the rotor's pitch angle, which is also accompanied by an increase in spinning rate. Precise and in operando control of the spinning axis angle is expected to have considerable advantages to future implementation of MAS within narrow-bore magnets, and for variable angle spinning (VAS) and dynamic angle spinning (DAS) experiments.

样品旋转轴的精确对齐对于许多魔角旋转固态 NMR 实验至关重要。球形转子是魔角旋转核磁共振的新范式，已被证明旋转稳​​定，转子崩溃的风险很小，但与圆柱形转子一样，它们以前仅使用机械调整方法将样品的旋转轴设置为魔角。在这里，我们展示了通过在定子内使用第二个气孔，球形转子的旋转轴可以精确地围绕魔角倾斜，而无需机械调整或运动定子。d _{4 中}羧酸氘核共振的² H MAS 边带线形通过将实验数据与模拟线形进行比较，丙二酸被用作转子在魔角上方或下方的绝对偏差的量度。我们观察到角度调节气体流量和转子的桨距角之间存在线性、单调关系，这也伴随着旋转速率的增加。精确和可操作地控制旋转轴角度有望对未来在窄孔磁体中实现MAS以及可变角旋转（VAS）和动态角旋转（DAS）实验具有相当大的优势。