• Record a conventional ¹H-decoupled ¹³C spectrum.

From the standard ¹³C spectrum file, create a new dataset with and change the pulse program to pulprog apt. 

See  90 degrees ¹³C observe pulse and 90 degrees ¹H decouple pulse calibrations.

Set the initial p0 ¹³C pulse to 45 degrees.

The interpulse delay (d20) is optimized according to the desired carbon multiplicity. A typical value is d20=7.1m (for ¹J_CH=140Hz):
        1/(¹J_CH)  C, CH₂ positive, CH, CH₃ negative
        1/(2¹J_CH) C only

The d21 delay define a short second echo (100 usec to 1msec).

Set ns as a function of the sample concentration.

(au_zg)) (proc_1d).

Carbon multiplicity selection can be also elucidated from other improved experiments as, for instance, DEPT experiments.