Fermi

Author: Xie Zunxiu
Publisher:
Publish Date: 2004-01-01
Features: Fermi, Italy--United States physicist Fermi is undoubtedly one of the greatest Italian scientists since Galileo and one of the most creative physicists in the world between 1925 and 1950. Fermi won the Nobel Prize in Physics in 1938 for "the discovery of new radioactive substances and the discovery of the selective absorption of slow neutrons." Fermi was born on September 29, 1901, in Rome. Fermi was intelligent and quick-witted, showing great talent from an early age, and was admitted to the Normal School in Pisa in 1918. He later graduated from the University of Pisa and received a Ph.D. in philosophy in 1924. After spending some time in G?ttingen and Leiden, he returned to Italy and was appointed as a professor of physics at the University of Rome. This was undoubtedly due to his already published approximately 30 important papers and the support of Corbino, one of the most outstanding physicists and senators in Italy at that time. Fermi began with the publication of the modern physics textbook Introduction to Atomic Physics, and his reputation quickly attracted the best young physicists in Italy around him. However, the rise of Italian fascism led to the exodus of Italian scientific talent. By 1938, Fermi was forced to move to the United States because his wife was Jewish. Before leaving Italy, Fermi had already become an astonishingly productive scientist during his time in Rome, making significant contributions in both theoretical and experimental fields. His experimental work stemmed from attempts to advance the work of the Joliot-Curie couple, who had already pointed out in 1934 that bombarding boron and aluminum with helium nuclei (α particles) would produce artificial radioactive isotopes. Fermi thought that the neutron discovered by James Chadwick in 1932 might be a better tool for creating new isotopes. Although neutrons are lighter than α particles, they are electrically neutral, which allows them to overcome the positive charge of a target nucleus without consuming the neutron's energy. Fermi reported that in 1934, he impulsively inserted paraffin between the neutron source and the target, placing it in front of the incident neutrons. The result was an increase in activation intensity by tens to hundreds of times. This was Fermi's accidental discovery of the slow neutron phenomenon. The production of slow neutrons later had a profound impact on both civilian and military nuclear energy. However, Fermi's direct task was to irradiate as many elements as possible with slow neutrons, producing and studying a large number of newly created radioactive isotopes and their properties. During the systematic irradiation of various elements, Fermi and his colleagues naturally bombarded uranium with slow neutrons. This inevitably led to nuclear fission, and Fermi called the newly produced super-heavy elements "ausoninum" and "hesperium." In 1938, Otto Hahn and Lise Meitner were the first to realize that nuclear fission was occurring in such reactions. In theoretical terms, Fermi's main achievement during his time in Rome was his theory of β decay. This is a process in unstable nuclei where a neutron transforms into a proton, emitting an electron and an antineutrino. Fermi conducted a detailed analysis, introducing a new force in science, known as the "weak" force. After coming to the United States, Fermi was eager to attempt to create a controlled chain nuclear reaction. In 1942, he successfully built the first nuclear reactor on the Stagg Field in the stadium at the University of Chicago. He and his colleagues used pure graphite as a moderator to slow down the neutrons and enriched uranium as fissile material to begin building the reactor. At 2:20 p.m. on December 2, 1942, Fermi's reactor achieved criticality, sustaining a self-sustaining chain reaction for 28 minutes, marking the beginning of the atomic age. In July 1945, when the first experimental atomic bomb exploded in the desert of New Mexico, Fermi was also present. It is said that when the wind blew in his face, he dropped some pieces of paper, and based on their displacement, he calculated that the bomb had the explosive power equivalent to 10,000 tons of TNT. After the war, Fermi served as a professor of physics at the University of Chicago until he died of cancer. Fermi is commemorated in physics in various ways: the 100th element is named "fermion"; the unit of length 10^-13 cm is called a "fermi"; and the National Accelerator Laboratory near Batavia, Illinois, is named the Fermi National Accelerator Laboratory.