Measure normal ¹H and ¹³C NMR spectra and obtain the offsets. Load a pulse program as shown, which combines measurement with proton irradiation at two different proton offsets and which stores the two FIDs separately. This procedure ensures that the instrument performance is exactly the same in the two experiments. You have to set:

decoupler power for c.w. decoupling
td	1 k (short aq, to avoid NOE build-up during acquisition)
sw	500 Hz
o1	on resonance of ¹³C signal of cyclohexane
o2	provide an ¹H frequency list for the pulse program, first value 200 kHz off resonance, second value on resonance of ¹H signal of cyclohexane
p1	90° ¹³C transmitter pulse
d1	200 s (10 times the relaxation time of cyclohexane)
ns	4

5. Processing

The experiment yields two FIDs which must be processed absolutely identically. Use a large line-broadening value of lb = 3 Hz to obtain spectra with good signal-to-noise ratio. Measure the two integrals and divide one by the other to obtain η + 1.

6. Result

Cyclohexane carbon-13 spectra without and with heteronuclear NOE

The figure shows the spectra without (a) and with NOE (b) obtained on an AM-400 spectrometer. From integrals η + 1 is determined to be 2.84.