Figure 7.

Position dependence of a CP-generated ¹³C signal intensity simulated assuming the RF inhomogeneity profile of the 3.2 mm probe for three MAS frequencies and three sizes of the ¹³C RF irradiation ramp. During the CP irradiation the ${\nu }_{1H}^{\mathit{cent}}$ amplitudes were 70 kHz at 20 kHz MAS, 110 kHz at 60 kHz MAS, and 40 kHz at 100 kHz MAS. For the 0%, ±20%, and ±60% ramps, ${\nu }_{1C}^{\mathit{cent}}$ was optimized for ZQ-CP at 20 kHz MAS to 47, 47, and 57 kHz; for ZQ-CP at 60 kHz MAS to 47, 47, and 61 kHz; and for DQ-CP at 100 kHz MAS to 62, 70, and 75 kHz, respectively. The DCC was 22.5 kHz and the CP contact time was 1 ms.