What is "magnetic resonance"

magnetic resonance \magnetic resonance\ n. (Physics) A phenomenon resulting from quantization in the magnetic field of electrons or atoms or molecules or nuclei exposed to an external magnetic field, by which a narrow frequency band of radio waves may be absorbed and re-emitted by the object.

n. resonance of electrons or atoms or molecules or nuclei to radiation frequencies as a result of space quantization in a magnetic field

Magnetic resonance can mean:

• Nuclear magnetic resonance, a physical phenomenon
• Magnetic resonance imaging
• Electron paramagnetic resonance

Magnetic resonance is a phenomenon that affects a Magnetic dipole when placed in a uniform static magnetic field. Its energy is split into a finite number of energy levels, depending on the value of quantum number of angular momentum. This is similar to energy quantization for atoms, say in H atom; in this case the atom, in interaction to an external electric field, transitions between different energy levels by absorbing or emitting photons. Similarly if a magnetic dipole is perturbed with electromagnetic field of proper frequency(E/h ), it can transit between its energy eigenstates, but as the separation between energy eigenvalues is small, the frequency of the photon will be the microwave or radio frequency range. If the dipole is tickled with a field of another frequency, it is unlikely to transition. This phenomenon is similar to that, when a system is acted on by a periodic force of frequency equal to its natural frequency.