Rotary resonance recoupling for half-integer quadrupolar nuclei in solid-state nuclear magnetic resonance spectroscopy

The reintroduction of various interactions such as chemical shift anisotropy (CSA), heteronuclear dipolar (HTD) and homonuclear dipolar (HMD) terms involving quadrupolar nuclei were investigated under rotary resonance (RR). When the signal from the central transition coherence (CTC) of half-integer quadrupolar nuclei under spin-locking condition provided by a low rf field and a high spinning speed was sampled stroboscopically at integer multiples of the rotor period, the quarupolar broadening mechanism disappears under the dual rf-spinning modulations. This paper demonstrates experimental evidence and a theoretical framework incorporating an average Hamiltonian theory (AHT) to explain various recouplings involving quadrupolar nuclei under various RR conditions.