Note: The Nyquist sampling theorem states that an FID or interferogram must be sampled at a rate at least twice the highest frequency in the FID or interferogram in order to reproduce the correct frequencies in an NMR or Fourier-transform infrared spectrum, respectively, without folding (folding (in spectroscopy)) artefacts. $f_{\mathrm{N}\mathrm{y}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{s}\mathrm{t}}=½\nu$.