MAS NMR with a spherical rotor in a 10 mm NMR tube

• solid-state NMR in a solution state probe • spinning axis can be adjusted using spinning gas Magic-angle spinning (MAS) partially averages anisotropic interactions in the NMR spin Hamiltonian to improve spectral resolution of solid samples. MAS requires the sample to be spun precisely about an angle of 54.74° with respect to the magnetic field. This technique introduces components within MAS NMR radiofrequency probes that are distinguishable from their solution-state counterparts - most notably, a stator that spins and sets the angle of spinning axis. Here, we present an MAS stator that spins and pneumatically sets the spinning axis angle of a 6 mm spherical rotor (65µL sample volume) while inside a 10 mm solution-state NMR tube. 79 Br experiments are used to verify the pneumatic adjustment and stability of the spinning angle, with 79 Br spinning echoes from KBr observed out to 8 ms. Utility for solid state MAS NMR is then demonstrated by a 31 P experiment of a proton-free inorganic phosphate, K 4 P 2 O 7 . Although this stator is applied here as an MAS insert that expands the utility of a solution-state probe, its space-efficient design is advantageous for any spinning experiments with a restricted volume.