Nuclear magnetic resonance (NMR) is the effect produced when a radiofrequency field is imposed at right angles to a (usually much larger) static magnetic field to perturb the orientation of nuclear magnetic moments generated by spinning electrically charged atomic nuclei. When the perturbed spinning nuclei interact with the very large (10,000-50,000 gauss) static magnetic field, characteristic spectral shifts and fine structure are produced that reflect the molecular or chemical environment seen by the nucleus. Hydrogen nuclei, fluorine, carbon-13, and oxygen-17 all have distinctive magnetic properties that make them suitable for NMR studies.

The sensitivity of nuclear magnetic resonance to molecular structure has made it a valuable research tool in organic chemistry, enabling chemists to determine hydrogen locations in crystals, something that cannot be done using x-ray diffraction. Nuclear magnetic resonance has also been used to study electron densities, chemical bonding, the compositions of mixtures...