Enrico Fermi (29.09.1901-28.02.1954) — an Italian physicist, a member of the Accademia dei Lincei (1935). He was born in Rome. He graduated from the University of Pisa (1922). In 1923 he worked at the University of Göttingen with M. Born, in 1924 at the University of Leiden with P. Ehrenfest, then taught at the Universities of Rome and Florence, and from 1926 was professor at the University of Rome. In 1938 he emigrated to the USA. In 1939 — 42 he was professor at Columbia University, in 1942—45 at the University of Chicago (in 1944—45 head of a division at the Los Alamos laboratory). From 1946 he was professor at the Institute for Nuclear Studies (Chicago).
His work was in atomic and nuclear physics, statistical mechanics, cosmic-ray physics, high-energy physics, astrophysics and technical physics. In 1925 (December) he developed (independently of P. Dirac) the statistics of particles with half-integer spin (Fermi — Dirac statistics), and in 1928 he gave an approximate scheme for describing and calculating the ground state of many-electron atoms (the Thomas —Fermi model of the atom). He is one of the founders of quantum electrodynamics and developed (1929— 30) the canonical rules of field quantisation (an approach different from the Heisenberg — Pauli scheme). In 1933 — 34 he created a quantitative theory of beta decay, which began the theory of weak interactions. In 1934 he discovered artificial radioactivity caused by neutrons, detected the phenomenon of the moderation of neutrons and gave its theory (Nobel Prize, 1938). He put forward the idea of obtaining new (transuranic) elements by irradiating uranium with neutrons, and in 1936 discovered the selective absorption of neutrons. These experimental works of Fermi with his collaborators (E. Amaldi, B. Pontecorvo, F. Rasetti, E. Segrè) began neutron physics.
In 1939 he created a quantitative theory of the ionisation energy losses of charged particles that takes the polarisation of the substance into account. At the same time, independently of F. Joliot-Curie, L. Szilard and others, he proved experimentally that when uranium nuclei undergo fission by slow neutrons, 2 — 3 new neutrons are emitted, and proved that a chain nuclear reaction of uranium fission is possible. He was the first to register (1941) the neutrons emitted in spontaneous fission. Together with H. Anderson he carried out a series of studies of the moderation and diffusion of neutrons in graphite and developed a method of determining the critical dimensions of the reacting medium (Fermi's exponential experiment).
He built the first nuclear reactor and on 2 December 1942 was the first to start it up, obtaining a self-sustaining chain reaction. He began neutron optics and neutron spectroscopy. In the last years of his life Fermi's research was for the most part in high-energy physics. In 1949 he revealed the mechanism of the acceleration of primary particles in cosmic rays and developed a theory of the origin of cosmic rays, and in 1950 a statistical theory of the multiple production of particles (mesons). He studied the interaction of pions with protons and in 1952 discovered the first hadron resonance — the isotopic quadruplet. Together with C. Yang he proposed in 1949 the first composite model of elementary particles, in which nucleons and antinucleons were treated as the fundamental particles (the Fermi — Yang model).
A member of many academies of sciences and scientific societies, a foreign member of the USSR Academy of Sciences (1929). The 100th chemical element, fermium, is named in his honour, a prize named after E. Fermi was established in the USA, and his name was given to the Chicago Institute for Nuclear Studies.
He created a large school of physicists (E. Amaldi, F. Rasetti, E. Segrè, E. Persico, B. Pontecorvo, G. Bernardini, G. Wick, E. Majorana, B. Rossi, G. Racah, G. Occhialini and others, the end of the 1920s and the 1930s, Rome; H. Anderson, M. Gell-Mann, R. Garwin, M. Goldberger, T. Lee, C. Yang, G. Chew, O. Chamberlain, M. Rosenbluth, J. Steinberger and others, the 1940s and 1950s, Chicago).
His work was in atomic and nuclear physics, statistical mechanics, cosmic-ray physics, high-energy physics, astrophysics and technical physics. In 1925 (December) he developed (independently of P. Dirac) the statistics of particles with half-integer spin (Fermi — Dirac statistics), and in 1928 he gave an approximate scheme for describing and calculating the ground state of many-electron atoms (the Thomas —Fermi model of the atom). He is one of the founders of quantum electrodynamics and developed (1929— 30) the canonical rules of field quantisation (an approach different from the Heisenberg — Pauli scheme). In 1933 — 34 he created a quantitative theory of beta decay, which began the theory of weak interactions. In 1934 he discovered artificial radioactivity caused by neutrons, detected the phenomenon of the moderation of neutrons and gave its theory (Nobel Prize, 1938). He put forward the idea of obtaining new (transuranic) elements by irradiating uranium with neutrons, and in 1936 discovered the selective absorption of neutrons. These experimental works of Fermi with his collaborators (E. Amaldi, B. Pontecorvo, F. Rasetti, E. Segrè) began neutron physics.
In 1939 he created a quantitative theory of the ionisation energy losses of charged particles that takes the polarisation of the substance into account. At the same time, independently of F. Joliot-Curie, L. Szilard and others, he proved experimentally that when uranium nuclei undergo fission by slow neutrons, 2 — 3 new neutrons are emitted, and proved that a chain nuclear reaction of uranium fission is possible. He was the first to register (1941) the neutrons emitted in spontaneous fission. Together with H. Anderson he carried out a series of studies of the moderation and diffusion of neutrons in graphite and developed a method of determining the critical dimensions of the reacting medium (Fermi's exponential experiment).
He built the first nuclear reactor and on 2 December 1942 was the first to start it up, obtaining a self-sustaining chain reaction. He began neutron optics and neutron spectroscopy. In the last years of his life Fermi's research was for the most part in high-energy physics. In 1949 he revealed the mechanism of the acceleration of primary particles in cosmic rays and developed a theory of the origin of cosmic rays, and in 1950 a statistical theory of the multiple production of particles (mesons). He studied the interaction of pions with protons and in 1952 discovered the first hadron resonance — the isotopic quadruplet. Together with C. Yang he proposed in 1949 the first composite model of elementary particles, in which nucleons and antinucleons were treated as the fundamental particles (the Fermi — Yang model).
A member of many academies of sciences and scientific societies, a foreign member of the USSR Academy of Sciences (1929). The 100th chemical element, fermium, is named in his honour, a prize named after E. Fermi was established in the USA, and his name was given to the Chicago Institute for Nuclear Studies.
He created a large school of physicists (E. Amaldi, F. Rasetti, E. Segrè, E. Persico, B. Pontecorvo, G. Bernardini, G. Wick, E. Majorana, B. Rossi, G. Racah, G. Occhialini and others, the end of the 1920s and the 1930s, Rome; H. Anderson, M. Gell-Mann, R. Garwin, M. Goldberger, T. Lee, C. Yang, G. Chew, O. Chamberlain, M. Rosenbluth, J. Steinberger and others, the 1940s and 1950s, Chicago).