Magnetic resonance

Magnetic resonance is the resonant absorption of electromagnetic energy by nuclei or other systems in a magnetic field. The resonance frequency depends on the system and the field strength.

Larmor precession: The precession of a magnetic moment around an applied magnetic field at a frequency proportional to field strength. Its frequency sets where magnetic resonance occurs for a given system and field.
Magnetic moment: A vector quantity that measures the strength and orientation of a source of magnetism. Magnetic moments couple to the applied field and make resonance possible.
Nuclear magnetic resonance spectroscopy: An analytical technique that uses nuclear magnetic resonance signals to determine molecular structure and dynamics. Chemical shifts and spin interactions turn resonance frequencies into molecular information.
Electron spin resonance: An alternative name for electron paramagnetic resonance, the magnetic resonance of unpaired electron spins. It concerns electronic rather than nuclear spins, despite sharing the underlying resonance mechanism.
Nuclear spin: An intrinsic quantum angular momentum carried by atomic nuclei, associated with magnetic moments in many isotopes. Nuclear magnetic resonance arises from the energy levels associated with nuclear spin.
Magnetic field: A vector field describing magnetic forces and their effects on moving charges and magnetic materials. Its strength sets the energy splitting and resonance frequency.
Magnetic resonance imaging: A medical imaging technique that uses nuclear magnetic resonance signals, magnetic-field gradients, and spatial encoding. It converts spatially varying resonance signals into images of internal anatomy.
Ferromagnetic resonance: The resonant precession of magnetization in a ferromagnetic material under an applied alternating field. It is a collective magnetic resonance in materials rather than a single-nucleus transition.
Zeeman effect: The splitting of energy levels when a system is placed in a magnetic field. The field splits spin energy levels, enabling absorption at a characteristic resonance frequency.
Electromagnetic radiation: Energy that propagates through space as coupled electric and magnetic fields. Resonant systems absorb radiation when its frequency matches an allowed energy gap.

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Norman Ramsey Jr.Related: Ramsey extended resonance techniques that grew from early nuclear magnetic resonance experiments.