Apodization/Weighting Function

The Apodization or Weighting Function is the mathematical function that the FID is multiplied by before Fourier Transform.

The Apodization functions improve data quality by removing non-random noise created by FID truncation and potentially increase signal to random noise or resolution by weighting different parts of the FID.

The Apodization menu is located under the Processing tab then Apodization.

H1 1D spectra often do not need Apodization.

C13 1D are often improved with the signal-to-noise enhancement of Exponential with ~1.0 Hz.

2D Spectra require use of Apodization in both dimensions. The optimum function differs depending upon the experiment.
For 2D Apodization see: 2D Apodization/Weighting Function


1) Truncation. An FID is truncated if there is still signal on the last point of the FID. The Fourier Transform of this is a step function, which gives sinusoidal noise on either side of the resonances that are truncated. To fix this, Select Exponential, then choose a value in Hz. Typically 0.2 Hz to 1.0 Hz is sufficient.

2) Increase Signal-to-Noise. To increase Signal-to-Noise. The Exponential with 0.2 Hz to 1.0 Hz is often optimal. However, the broader the natural line-width of the resonance, the larger the value in Hz that you should choose. If you are trying to find a resonance broadened, possibly by exchange or proximity to paramagnetic material, a larger value of Hz will increase the signal-to-noise.

3) Increase Resolution. To increase resolution, try using a Gaussian Function with a negative value of Hz, ~-0.1 to -0.3 Hz. This can improve the line-width at half maximum and give better resolution of resonances. The disadvantage of this is that it will start to create baseline distortions and truncation artifacts.