NMR is based on the emission and absorption of energy in the
radiofrequency range of the electromagnetic spectrum. All nuclei that
contain odd numbers of protons or neutrons can be observed with
NMR. The most commonly measured nuclei are 1H and 13C, although
nuclei from the isotopes of many other elements can be observed
(23Na, 31P, etc.). NMR aligns magnetic moments with an applied constantmagnetic
field and disturbs this alignment using an orthogonal alternating
radiofrequency magnetic field. This disturbance induces a
resonant phenomenon which is used in NMR measurements and magnetic
resonance imaging (MRI)