Formation and identification of pure intermolecular zero-quantum coherence signal in liquid NMR

A new pulse sequence with three radio-frequency pulses was designed to detect NMR signals originating from pure intermolecular zero-quantum coherence (iZQC) in isolated spin-1/2 samples such as water. Analytical expressions were derived from the modified Bloch equations with dipolar fields. All the experimental observations and simulated results demonstrate that the iZQC signals can be selectively detected, mostly free of contamination of other coherences and conventional signals. Compared to the two-pulse CRAZED sequence, the new sequence is insensitive to the imperfection of flip angles.