(1905–89), Italian-born U.S. physicist. Born in Tivoli, Italy, Segrè came to the United States in 1938 as a research associate at the University of California, Berkeley, and became a United States citizen in 1944. He was a professor of physics at Berkeley from 1945 to 1972. In 1955, Segrè and Owen Chamberlain discovered the antiproton, for which the two shared the 1959 Nobel prize in physics. In addition, Segrè helped discover new elements—technetium (the first artificial element not found in nature), astatine, and plutonium-239 (now commonly used in nuclear reactors and nuclear weapons). He also explored the role of the neutron in splitting the atom and developed a chemical method for dividing nuclear isomers. (See also Physics.)