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Rabi, Isidor Isaac

magnetic atomic columbia resonance

(1898–1988) Austrian–US physicist: developed molecular beam experiments.

Rabi grew up in the Yiddish community of New York, studying at Cornell and Columbia Universities. He obtained a professorship at Columbia in 1937 and remained there until retirement.

During a brief period (1927–9) working with , Rabi was greatly impressed by the recent Stern–Gerlach experiment. Starting a research programme at Columbia, Rabi invented the atomic-and molecular-beam magnetic resonance methods of observing spectra. In this a constant magnetic field excites the molecules into a set of states and a radio wave signal of the right frequency can resonantly flip the molecule from one magnetic state to another. The magnetic properties of the molecule or atomic nucleus may then be found accurately. The magnetic moment of the electron was measured in this way to nine significant figures, thereby testing the theory of quantum electrodynamics (QED). The technique was also a precursor of the NMR (nuclear magnetic resonance) method developed by , and has also been applied to an atomic clock, nuclear magnetic resonance, the maser and the laser. Rabi won the 1944 Nobel Prize for physics for this work.

During the Second World War Rabi worked on microwave radar and afterwards was concerned with administration and scientific policy-making, serving as chairman of the General Advisory Committee of the Atomic Energy Commission and as a member of the delegation to UNESCO which founded CERN (laboratory in Geneva for high-energy physics).

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