The NOESY block allows to transfer magnetization between spins via dipolar coupling or chemical exchange processes in the longitudinal axis. It consists of the 90º-delay-90º cluster in which NOE and exchange transfer are achieved during the mixing time.

The process follows as:

• Before the NOESY block, in-phase transverse magnetization of the target spin (I_1x) is required.
• A 90º pulse creates longitudinal magnetization (I_1z).
• During the mixing time the magnetization is transferred to other spins via dipolar coupling or exchange processes  (I_2z+ I_3z + I_4z ...).
• A final 90º creates the desired in-phase transverse magnetization of the relayed NOE spins (I_2x+ I_3x + I_4x ...).

On the other hand, analogous building blocks can be designed by incorporating several elements during the mixing time:

• A short and intense PFG  (see noesygpph).
• A weak PFG through all mixing time.
• Solvent saturation using a low-power continuous irradiation (see noesyphpr).

Easy implementation on AVANCE spectrometers.

 The most important parameter to optimize is the mixing time (d8).

The standard way to implement a NOESY block is:

... p1 ph1 d8 p1 ph2 ...

in which:

• p1 is the 90 1H pulse (in usec) applied at high power level pl1 from the f1 channel.
• d8 is the mixing NOESY time (in seconds).
• All phases may be specified at the end of pulse program.

  See  2D NOESY and related experiments.