• Record a conventional 1H spectrum. Note the frequencies to be irradiated.

a ¹H-¹H NOEDIFF spectrum with rpar NOEDIFF all (the pulse program zgf2pr

NOE experiments are recorded without sample spinning.

If executed manually, set o2p on resonance for the selected resonance in the first experiment and in a blank region in the second experiment.

The power level and the duration of the irradiation are defined by  pl14 (depends of the required selectivity, start with 70 dB) and d20 (6 s), respectively.

If executed manually,

In automation mode, execute the AU program defined in AUNM au_noediff or noediff

NOE difference spectra can be processed in different ways. Since one wants to observe signal intensity changes of 2% to 10%, one should use an exponential window function (ef) with lb=2 Hz to minimize artefacts of substraction. One can either transform the two spectra separately using a digitally indentical phase correction and substract the two spectra, or, more conveniently, substract the two FIDs directly from each other. In the difference spectrum, adjust the phase of the large signal to be negative. Evaluate only signals which have correct phase and have therefore not been affected by inadequate spectrometer stability.

In automation mode, execute the AU program defined in the processing parameter AUNMP, proc_noe.

If several frequencies must be irradiated, use the pulse program noedif.2. In this case a frequency list to define irradiation frequencies (FQ2LIST=noedif.1) must be defined from the frqlist subroutine. Other parameters to consider:

parmode= 2D
l4=td1 = number of irradiation frequencies (or experiments)
l5 loop for averaging: total number of scans = ns * l5
Start acquisition with zg and process all spectra by executing the AU splitser and multiefp Au programs.

On the other hand, the same experiment can be recorded with multiple selective irradiation on a specific multiplet (pulprog noemul) in automation mode by executing xau noemult.