Nier, << neer, >> Alfred Otto Carl (1911-1994), an American physicist, won distinction for his development of a mass spectrograph and his use of it in nuclear research. He specialized in the study of isotopes (atoms of the same element with different masses) and the accurate determination of their masses. An atom’s mass is the amount of matter it contains.
Nier separated a small amount of the two principal isotopes of uranium, U-235 and U-238, in 1940. This enabled physicist J. R. Dunning and his associates at Columbia University to prove that U-235 fissions (splits) when bombarded with slow neutrons. This discovery ranks as a milestone in the development of practical atomic energy. Nier also studied thermal diffusion, electronics, and the application of the mass spectrograph to chemistry, geology, and medicine.
Nier was born on May 28, 1911, in St. Paul, Minnesota. He graduated from the University of Minnesota. He became chairman of the physics department there in 1953 and taught at the university until 1980. He died on May 16, 1994.
See also Dunning, John Ray ; Isotope .
