Fig. 7.

Simulated selectivity of the sine modulated scheme (e.g. Fig. 1II) as a function of offset and modulation frequency ω_m. The SPINEVOLUTION [59] was used for the simulations. For simplicity, a constant ¹⁵N RF-field was utilized, and the spin system was ¹⁵N–¹³C, with a distance of r_C–N = 1.448 Å. The chemical shift parameters for ¹³C were δ_iso = 0 ppm, δ_aniso = 24 ppm, η = 0.92; for ¹⁵N, δ_iso = 0 ppm, δ_aniso = 100 ppm, η = 0.8. In the simulations, ω_1N = 9 kHz, ${\omega }_{1\text{C}}^{max}=6\text{kHz}$, and the MAS rate of 11 kHz were used. The maximum intensity in this plot was normalized to 1.