Cowinner with Owen Chamberlain of the U.S. of the 1959 Nobel Prize for Physics for the discovery of the antiproton, an antiparticle having the same mass as a pronton but opposite in electrical charge.
In 1932 Segrè was appointed assistant professor of physics at the University of Rome and two years later he participated in neutron experiments directed by the noted physicist Enrico Fermi in which many elements including uranium were bombarded with neutrons and transuranic elements (elements heavier than uranium) were created.
In 1935 they discovered slow neutrons which haver properties important to the operation of nuclear reactors.
But it remained for others to discover nuclear fission four years later.
Segrè left Rome in 1936 to become director of the physics laboratory at the University of Palermo.
One year later he discovered technetium, the first manmade element not found in nature.
While visiting California in 1938 he was dismissed from the University of Palermo by the Fascist government so he remained in the U.S. as a research associate at the University of California Berkeley.
Continuing his research he and his associates discovered the element astatine in 1940 and later with another group he discovered plutonium-239 which he determined is fissionable muck like uranium-235.
Plutonium-239 was used in the first atomic bomb and in the bomb dropped on Nagasaki.
From 1943 to 1946 he was a group leader at the Los Alamos N.M. Scientific Laboratory.
He was naturalized as a U.S. citizen in 1944 and he became professor of physics at Berkeley in 1946.
In 1955 using the new bevatron particle accelerator Segrè and Chamberlain succeeded in producing and identifying antiprotons and thus set the stage for the discovery of many additional antiparticles.
His book Nuclei and Particles was published in 1964.