Homonuclear Multiple Quantum Coherences (MQCs) can be created by applying a mixing pulse when antiphase single-quantum-coherences (SQCs) of coupled spin systems have been previously created. Thus the basic homonuclear MQ block consists of

• The first 90º pulse creates SQCs.
• During the interpulse delays, magnetization only evolves under the effect of J_HH. The 180º pulse removes chemical shift evolution and each interpulse delay is optimized to 1/4*J_HH.
• The second 90º pulse creates MQCs.

Examples that use the MQ block as a preparation period are, for instance, the 2D Double-Quantum (DQ) and 2D Zero-Quantum (ZQ) experiments. This block can also be applied to other nuclei (¹³C) as found in the 2D INADEQUATE experiment.
 

Easy implementation on AVANCE spectrometers.

To select only even orders of coherence, the two 90º pulses must have the same phase. On the other hand, to select only odd orders of coherence, the phase of the first 90º pulse must be shifted by 90º degree relative to the second 90º pulse.

For further details about implementation of MQC-based experiments in AVANCE spectrometers see, for instance:

Tutorial: 2D Double-Quantum (DQ) experiment
Tutorial: 2D INADEQUATE experiment

The basic element can be written as:

... p1 ph1 d4 p2 ph2 d4 p1 ph3 ...

in which p1 and p2 are the 90º and 180º pulses, respectively, applied at high power level (pl1), the phases will be specified at the end of pulse program and d4 is set to 1/(4*J).

MQCs can be also generated in heteronuclear spin systems (see heteronuclear MQC).