free induction decay

noun

: a time-based electrical signal that is detected in a nuclear magnetic resonance spectrometer, that is produced by induction from the motion of the magnetic moments of nuclei, that decays with time, that can be converted to a more conventional frequency-based signal using analysis by Fourier transforms, and that with a suitable display can be used to extract more information from a test sample or subject than is possible in conventional nuclear magnetic resonance spectroscopy

—abbreviation FID