Figure 12.

Effective nutation frequencies ${\mathit{\nu }}_{\mathrm{eff}}$ over a MAS period during FSLG decoupling as a function of the position within the 3.2  $\mathrm{mm}$ MAS probe for C2, C3, and C4. Effective fields were extracted from interaction frame trajectories computed for a field strength of 125  $\mathrm{kHz}$ along the magic angle and a MAS frequency of 12.5  $\mathrm{kHz}$ . Small effective fields of up to 50  $\mathrm{Hz}$ arise for rf amplitude and phase modulations alone (C2 and C3). Substantially larger fields up to 400  $\mathrm{Hz}$ are observed for combined modulations (C4). In general, effective fields of considerable size are only obtained at the rotor edges, and even the maximum resulting magnitudes remain small compared to the nominal rf field strength and the rotor frequency.