the phenomenon in which certain atomic nuclei possessing a magnetic moment will precess around the axis of a strong external magnetic field, the frequency of precession (Larmor frequency) being specific for each nucleus and the strength of the magnetic field; spinning nuclei induce their own oscillating magnetic fields, and therefore emit electromagnetic radiation that can produce a detectable signal at the Larmor frequency. NMR is used as a method of determining structure and assessing molecular dynamics and is applied clinically in magnetic resonance imaging.