Efficient Dipolar Double Quantum Filtering Under Magic Angle Spinning without a 1H Decoupling Field

We present a systematic study of dipolar double quantum (DQ) filtering in 13 C-labeled organic solids over a range of magic-angle spinning rates, using the SPC- n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n ⩾ 7, provided that the 13 C nutation frequency is on the order of 100 kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between 13 C and 1 H fields. For 13 C nutation frequencies greater than 75 kHz, optimal performance is observed without an applied 1 H field. At spinning rates exceeding 20 kHz, symmetry conditions as low as n = 3 were found to perform adequately.