Multiple Signals in Nuclear Magnetic Resonance
The fast Fourier transform (FFT) plays a crucial role in advanced nuclear magnetic resonance (NMR) spectroscopy. We show here how multiple signals are transformed for NMR.Three signals of different frequencies are considered. The free induction decay (FID) contains all three components and three peaks can be seen in the spectrum window. Such spectra closely resemble actual NMR experiments, with signal components of different frequencies usually arising from chemical shifts.
 Wikipedia. "Nuclear Magnetic Resonance." (Mar 5, 2012) en.wikipedia.org/wiki/Nuclear_magnetic_resonance.