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Purcell, Edward Mills

magnetic resonance interstellar physics

[per sel ] (1912–97) US physicist: developed nuclear magnetic resonance; and first detected the interstellar 21 cm microwave emission.

Purcell graduated from Purdue in electrical engineering and then studied physics at Karlsruhe and at Harvard, where he taught from 1938. During 1941–5 he worked on the development of microwave radar at Massachusetts Institute of Technology, returning to Harvard as professor of physics.

Purcell was instrumental in the late 1940s in developing nuclear magnetic resonance (NMR) methods for measuring the magnetic moments of atomic nuclei, in solids and liquids. Any atomic nucleus with spin (such as hydrogen or fluorine) will, if held in a powerful magnetic field, absorb radiation in the radiofrequency range by a resonance effect, and measurement of this has given valuable information on features of the absorbing nuclei and their molecular environment. This NMR method has since become a dominant method in chemistry for a variety of analytical purposes. For his work on NMR, Purcell shared the 1952 Nobel Prize for physics with .

In radio astronomy Purcell was in 1951 the first to report observation of the 21 cm wavelength microwave radiation emitted by interstellar neutral hydrogen. This was predicted theoretically by and has been used in the mapping of much of our Galaxy, and in deducing the temperature and motion of the interstellar gas.

Purkinje, Johannes (Evangelista) [next]

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