Isidor Isaac Rabi


Isidor Rabi was awarded the 1944 physics Nobel prize "for his resonance method for recording the magnetic properties of atomic nuclei.” Isidor Rabi discovered nuclear magnetic resonance, in which the nuclei, which have a magnetic moment and a spin, line up to a magnetic field, either spin up or spin down depending on the direction of the magnetic field. These two states, spin up and spin down, have two distinct energies as described by quantum mechanics. The difference in energy is a frequency in the radio range. If a radio frequency pulse is applied the spins flip, and when they go back, they emit a radio wave, which can be measured.