In heteronuclear experiments, a single refocusing pulse is often used to remove the effects of the heteronuclear coupling over a period. Thus, if a PFG is applied in the opposite sense, any coherences on I-spin will be rephased whereas the 180° pulse on S acts as a simple inversion pulse. The net effect is that the chemical shift of I-spin freely evolves during the overall duration of the two PFGs but the heteronuclear coupling is refocused.

See some examples:
 

Easy implementation on AVANCE spectrometers equipped with gradient technology.

The standard way to implement a heteronuclear decoupling element in a pulse program is:

... d13 p16:gp1 d16 (p4 ph1):f2 d13 p16:gp2 d16 ...

in which:

• p4 is the high-power 180 degree pulse from the f2 decoupler channel.
• p16 is the duration of the gradient (in microseconds)
• d16 is the recovery time (in seconds) needed after the gradient
• gp1 and gp2 stand for the gradient strength defined in the gpz1 and gpz2 commands, where gpz1=-gpz2. Otherwhise, gpnam1 and gpnam2 define the shape of the gradients.