Broadband magnetization transfer using moderate radio-frequency fields for NMR with very high static fields and spinning speeds

We introduce a new dipolar recoupling scheme, dubbed PARIS-xy (phase-alternated recoupling irradiation scheme using orthogonal radio-frequency phases), to promote efficient broadband magnetization exchange between 13C nuclei using moderate radio-frequency amplitudes at very high magnetic field strengths and spinning speeds. Experimental observations for a wide range of spinning frequencies 30 ⩽ νrot ⩽ 60 kHz and magnetic field strengths (B0 = 9.4, 17.6 and 21.2 T) are backed up by numerical simulations.