Shull, Clifford Glenwood (1915-2001), an American physicist, made important contributions to the development of neutron-scattering techniques for studies of matter. Neutrons are subatomic particles, which are released by the breakdown of atoms in a nuclear reactor. Working with Ernest Wollan, Shull developed the neutron diffraction technique. The two scientists showed that a stream of neutrons from a nuclear reactor could be used to study some crystals more effectively than X rays could. They developed the technique into a useful tool for researchers. For these developments, Shull shared the 1994 Nobel Prize in physics with Bertram Neville Brockhouse, who worked independently of Shull in the same field. Wollan had died in 1984, and so could not share in the Nobel Prize (the Nobel Prize is not awarded posthumously). See also Brockhouse, Bertram Neville .
Early in his career, Shull had used X-ray crystallography to deduce the arrangement of atoms in crystals from the scattering of X rays passed through the material. X rays are deflected by electrons in the outer part of an atom. Small atoms have few electrons and do not deflect X rays. As a result, X rays cannot reveal the arrangement of all kinds of atoms in crystals–most significantly, of hydrogen atoms. But, neutrons flowing through a crystal react with the nucleus of an atom, however small. Shull worked with Wollan for nearly ten years, during which they confirmed that neutrons could be used to study crystals in this way.
Shull was born in Pittsburgh, Pennsylvania, on Sept. 23, 1915. He was educated at the Carnegie Institute of Technology (now Carnegie Mellon University) in Pittsburgh, and majored in physics, where he graduated in 1937. He went on to study at New York University, using particle accelerators to study nuclear interactions. In 1941, he obtained his Ph.D. and in the same year joined an industrial company, studying the structure of catalysts (materials that promote chemical reactions) used in making aviation fuel. This work became of greater importance when, in 1941, the United States entered World War II.
In 1946, Shull moved to Tennessee to conduct nuclear research at what is now the Oak Ridge National Laboratory. There he worked with Ernest Wollan, who was trying to use neutrons in the way that X rays had previously been used to investigate crystals.
In 1955, Shull moved to the Massachusetts Institute of Technology (MIT), where he remained as a professor of physics until he retired in 1986. He died on March 31, 2001.
