Figure 2:

(a) ¹³C CPMAS pulse sequence. (b) XY8 phase cycling ¹³C{²⁹Si} REDOR pulse sequence with alternating π pulses on both channels. (c) ²⁹Si spin topology used in simulation of ¹³C{²⁹Si} REDOR data showing nearly 180° angles between ¹³C=O – ²⁹Si and ¹³C=O – ¹³C_α dipolar vectors. Arrow in the figure indicates the dipolar couplings that were varied in simulations. (d) ¹⁵N CPMAS pulse sequence. (e) XY8 phase cycling ¹⁵N{²⁹Si} REDOR pulse sequence with alternating π pulses on both channels.