The situation becomes a bit more complex for spin S > 1/2 half-integer quadrupolar nuclei. As described in the seminal work by A. Vega , magic-angle spinning induces level crossings between the satellite-transitions (STs) and the spinlock rf frequency. These brief crossings can cause leakages of polarization, therefore strong rf fields should be avoided for the spinlock. Low rf fields are usually used to reduce the deteriorating effect of the spinlock to the central-transition (CT) polarization during CP. Low rf fields not only limit the bandwidth with respect to frequency offsets but also restrict the 1 H rf field that can be used to match the Hartmann-Hahn (HH) CP conditions from being close to rotary resonances which interfere with the 1 H spinlock . For these reasons, pulsed methods using INEPT and HMQC have been explored for indirect detection and HETCOR of quadrupolar nuclei . The broad bandwidth obtained from using just two short pulses in HMQC offers opportunities for indirect detection of ST, multiple-quantum (MQ), and even overtone (OT) transitions of quadrupolar nuclei, including 14 N for which all single-quantum transitions are subject to large first-order quadrupolar broadening. In order to accelerate HMQC build-up, dipolar recoupling under MAS can be applied, namely D-HMQC, on the observed or indirect channel . When applied on observation channel, the dipolar recoupling also re-introduces the chemical shift anisotropy (CSA). Incomplete refocusing of the CSA due to spinning frequency fluctuations can cause t1noise particularly for recoupling sequences that are sensitive to the rotor angle . Improved pulse sequences named TONE-HMQC or by switching the recoupling to the indirect quadrupolar nuclei using the early-developed TRAPDOR , namely T-HMQC ,