What is the difference between NMR, MRI and ESR?

Asked by: A.V. Ravishankar Sarma

Answer

The acronyms:

NMR = Nuclear Magnetic Resonance is the resonance that occurs when a nucleus (usually hydrogen, but any nucleus that has non-zero spin will work) is placed in a magnetic field and is 'swept' by a radio frequency that causes the nuclei to 'flip'. This causes the radio frequency to be absorbed, which is what is measured.

MRI = Magnetic Resonance Imaging is a more complex application of NMR in which the geometric source of the resonances are detected and deconvoluted by Fourier transform analysis.

ESR = Electron Spin Resonance is also a resonance phenomenon, except in this case it is the spin of an unpaired electron that is in resonance, rather than a nuclear spin.
Answered by: Vince Calder, Ph.D., Physical Chemist, retired