"For the identification of new elements of radioactivity and the discovery of nuclear reactions using slow neutrons". This is the motivation with which the 10 December of the 1938, exactly 81 years old, the Royal Swedish Academy of Sciences awarded a Enrico Fermi, then 37 years old, the Nobel Prize for Physics. The research that earned the Italian scientist the highest recognition proved decisive for the subsequent development of atomic energy.
Born in 1901 in Rome, at the age of just 25 Fermi was already full professor of Theoretical Physics at the University of the capital. Together with his closest collaborators, known as the "boys of via Panisperna”, created a research center of primary international importance. From 1934 Fermi's group began to work on the artificial radioactivity, bombarding the nuclei of various chemical elements with neutrons. After the operation, the neutrons were absorbed by the bombarded nuclei, which then emitted a particle and gave rise to a new radioactive element, with an atomic number two units lower than the starting element.
But it's not over. On October 20, 1934, with an intuition that not even he was ever able to fully explain, Fermi modified the experiment as follows: instead of a lead wedge, between the neutrons and the target nucleus he inserted a piece of paraffin, a substance rich in hydrogen which proved to be able to slow down the neutrons, enormously increasing their effectiveness in producing the radioactivity of the target nucleus. They were the famousslow neutrons” which can also be read in the motivations of the Nobel.
Two weeks after receiving the award, the Italian physicist was forced to emigrate to the United States. The reason? His wife, Laura Capon, was Jewish. And Benito Mussolini had just launched racial laws.
