The incorporation of delays into NMR pulse sequences involving heteronuclear systems allow the free evolution of chemical shift and homo- and heteronuclear coupling constants similarly as the homonuclear case. Alternatively, 180º pulses placed into heteronuclear pulse sequences can be used to refocus a desired chemical-shift, homo- or heteronuclear J-coupling information, depending of the position into the pulse sequence and on the nuclei that they are applied.

Easy implementation on AVANCE spectrometers.

There are 32 duration parameters, d0-d31,  to be specified in seconds. They are executed as delays without any further actions by the pulse program commands d0. They can be incremented or decremented using the pulse program commands id0-id31 or dd0-dd31, respectively. The changes are given by the parameters IN0-IN31. The pulse program commands rd0-rd31 reset a respective delay to its original value. The delays may also be changed by means of arithmetic expressions during pulse program execution.

The most standard way to implement fixed delay in a pulse program is:

... d2 ...

Any delay found in any part of the pulse sequence can be used to change power levels, set frequencies and other utilities. However, BRUKER proposes a standard nomenclature for general use:

d0 : incremented delay (2D)                         [3 usec] d1 : relaxation delay; 1-5 * T1 d2 : 1/(2J) d3 : 1/(3J) d4 : 1/(4J) d5 : DE/2 d6 : delay for evolution of long range couplings d7 : delay for inversion recovery d8 : NOESY mixing time d9 : TOCSY mixing time d10: incremented delay (3D) d11: delay for disk I/O                             [30 msec] d12: delay for power switching                      [20 usec] d13: short delay                                    [3 usec] d14: delay for evolution after shaped pulse d15: d16: delay for homospoil/gradient recovery d17: delay for DANTE pulse-train d18: delay for evolution of long range couplings d19: delay for binomial water suppression d20: for different applications d21: for different applications d22: 1/(2J(XY)) d23: 1/(4J(XY)) d24: for different applications d25: 1/(6J(YH)) d26: 1/(4J(YH)) d27: d28: for different applications d29: for different applications d30: for different applications d31: for different applications