Zero-Fill

Zero-Filling is the process of adding data points to the end of the FID before Fourier Transform.

Zero-Filling can improve data quality by increasing the amount of points per ppm in the processed data to better define the resonance. The added data points have 0 amplitude so the only change of the processed data is more discreet data points.

The Zero-Fill menu is located under the Processing tab then Zero-Fill/LP. LP is Linear Prediction which is discussed here:
Forward Linear Prediction

Backward Linear Prediction


1D spectra are typically zero-filled to twice to four times the real data points acquired. The effect in 1D data is often small as large number of points are already acquired.

2D Spectra are zero-filled in both dimensions. Since minimal data points are acquired in 2D experiments, zero-filling is important.

For 2D Zero-Filling see: 2D Zero-Filling


1) To accomplish 1D Zero-Filling open the Zero-Fill/LP tab.

2) On the top left, the window will show the original amount of data points of the FID. To the right under To Spectrum Size, choose a number larger than the Original. That number is the number that the Fourier Transform will operate on. If the Original is 16384, then To Spectrum Size is 65536, that would be a 4X Zero-Fill. Typically any number beyond 4X will not help, but the only disadvantage of a larger Zero-Fill is the data size.

3) When using Zero-Fill, be sure the Spectrum Size is larger than the Original, else that is a negative Zero-Fill or truncation of the FID.

4) To best see the effects of the Zero-Fill, zoom in on a sharp resonance such as the solvent peak or a sharp singlet in the molecule. As you change the To Spectrum Size, see how the shape of the resonance changes.