Heteronuclear Multiple Quantum Coherences (MQCs) between two different nuclei, ¹H and X, can be created by applying a mixing X pulse when antiphase ¹H single-quantum-coherences (SQCs) with respect to ¹J_XH  have been previously created. Thus the basic heteronuclear MQ block consists of:

• The first 90º pulse creates ¹H SQCs.
• During the interpulse delay ( optimized to 1/(2*¹J_XH), magnetization only evolves under the effect of ¹J_XH. Simultaneous 180º ¹H and X pulses could be placed at the middle of this period to remove chemical shift evolution.
• The second 90º pulse creates ¹H-X MQCs.

This heteronuclear MQ block is applied in HMQC-type and HMBC-type experiments:

Easy implementation on AVANCE spectrometers.

For further details about implementation of HMQC experiments in AVANCE spectrometers see, for instance, Tutorial: 2D HMQC experiment

The standard way to implement an heteronuclear MQC scheme in a pulse program is:

... (p1 ph1):f1 d2 pl2:f2 (p3 ph2):f2 ...

in which p1 is the 90º ¹H pulse (in microseconds) applied at a power level pl1 from the f1 channel, d2 is the evolution period optimized to 1/(2*J(HX)), p3 is the  90º X pulse (in microseconds) applied at a power level pl2 from the f2channel, and all phases are specified at the end of pulse program.

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