Enrico Fermi

Enrico Fermi (1901-1954) was an Italian-born nuclear physicist and designer of the first nuclear reactor.

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Enrico Fermi

Fermi was a very broadly oriented physicist, in fact he was one of the last physicists who contributed equally important to theoretical and experimental physics. As a theorist, he contributed decisively to quantum mechanics (Fermi-Dirac statistics) and nuclear physics (theory of beta decay). As an experimentalist, he introduced the technique of neutron bombardment to study artificial radioactivity, opening the way to the discovery of nuclear fission. He established a famous school of nuclear physics in Rome, but left fascist Italy because of anti-Jewish legislation. In 1939 he settled in the United States, where he contributed to the atomic bomb program and served as an influential scientific adviser in postwar American nuclear policy. His name is honored in the unit of length for nuclear dimensions (the fermi, 10⁻¹³ cm), in the transuranic element of atomic number 100 (fermium), in a class of elementary particles (fermions), and in one of the most important particle physics laboratories in the world (Fermi laboratory, near Chicago).

Born in Rome on 28 November 1901 Fermi studied physics at the University of Pisa, as a fellow of the prestigious Scuola Normale Superiore. Soon after his graduation in 1922, the influential director of the Physics Institute of Rome University, Orso Mario Corbino, a former Minister of National Education and eventually (1923-1924) Minister of National Economy, realized his promise and promoted his career. Corbino sent Fermi to pursue his studies in Göttingen (1923) and Leiden (1924), and in 1926 obtained for him a chair of theoretical physics (the first in Italy) in the institute in Rome. That year Fermi published a seminal paper on the quantization of the monatomic ideal gas, proposing a new quantum statistics for particles with half-integral spin (fermions).

With Corbino's support, Fermi set up a brilliant research group in nuclear physics that included Edoardo Amaldi, Franco Rasetti, Emilio Segrè, Oscar D'Agostino, Bruno Pontecorvo, and Ettore Majorana. The group followed up the then-new phenomenon of artificial radioactivity by means of neutron bombardment of the chemical elements of the periodic table. Between March and July 1934, they "discovered" (that is, made and detected) about fifty new radionuclides. A few of these, which they misinterpreted as transuranic elements, turned out to be fission products of uranium, as Otto Hahn and Fritz Strassmann discovered four years later.

Also in 1934, Fermi found that neutrons slowed down in passing through light elements and that, when suitably retarded, they became extremely effective in provoking nuclear transmutations. No less important was Fermi's theoretical analysis of nuclear beta decay (1934), which invigorated the study of weak interactions. The Fermi group itself soon decayed. Most members left Rome and Corbino died in January 1937, thereby depriving Fermi of important institutional support. The fascist racial legislation of 1938 hit Fermi's Jewish wife, Laura Capon, and political boycott added to scientific frustration. Fermi decided to leave Italy. After he collected his Nobel Prize in Stockholm in December 1938 for his neutron work, he and his family sailed to New York. He became a U.S. citizen in 1944.

Initially established at Columbia University, Fermi moved to the University of Chicago in 1942 to work in the Manhattan Project. He led the construction of the first nuclear reactor, which went critical on 2 December, demonstrating the chain reaction and the feasibility of producing plutonium for an atomic bomb. He then collaborated with the Los Alamos teams involved in the construction of the bomb and attended the Trinity Test in Alamogordo, New Mexico, on 16 July 1945. After the war he served on the Atomic Energy Commission's General Advisory Committee, contributing to the definition of American nuclear strategy and research policy. He also spent time in Los Alamos in 1950 to work on the H-bomb program launched by President Harry Truman that January. But Fermi's main base was the University of Chicago, where he inaugurated an important research program in particle physics centered on a new 450 MeV synchrocyclotron. His team studied pion-nucleon interactions (1952-1953), confirming the conservation law of isotopic spin in strong interactions and observing the first pion-nucleon resonance.

In 1952 Fermi was elected president of the American Physical Society. He had to cope with the drama unleashed in the American scientific community by the anti-communist campaign of Senator Joseph McCarthy and the ensuing trial of J. Robert Oppenheimer before the Atomic Energy Commission's Security Board. He testified in April 1954 in support of the former scientific leader of Los Alamos. In the summer of 1954, Fermi fell ill with stomach cancer. After useless surgery, he died in Chicago on 29 November.

Bibliography

• Laura Fermi, Atoms in the Family (1954).
• Emilio Segrè, Enrico Fermi, Physicist (1970).
• Edoardo Amaldi, "Personal Notes on Neutron Work in Rome in the '30s and Post-War European Collaboration in High Energy Physics," in History of Twentieth Century Physics, ed. Charles Weiner (1977): 293-351.
• Gerald Holton, "Fermi's Group and the Recapture of Italy's Place in Physics," in Holton, The Scientific Imagination. Case Studies (1978): 155-198.
• Arturo Russo, "Science and Industry in Italy between the Two World Wars," Historical Studies in the Physical and Biological Sciences 16 (1986): 281-320.