A 4-mm Probe for 13C CP/MAS NMR of Solids at 21.15 T

The design of a broadband 4-mm magic-angle spinning (MAS) X–1H/19F double resonance probe for cross-polarization (CP)/MAS NMR studies at 21.15 T (1H at 900 MHz) is described. The high-frequency 1H/19F channel employs a new and efficient transmission line tuning design. The first 13C CP/MAS NMR spectra recorded at 21.15 T have been obtained with this probe and exhibit the best S/N per milligram sample of hexamethylbenzene achieved so far for a 4-mm rotor.