The Nobel Prize in Physics 1938
Born: 29 September 1901, Rome, Italy
Died: 28 November 1954, Chicago, IL, USA
Affiliation at the time of the award: Rome University, Rome, Italy
Prize motivation: "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons"
Field: nuclear physics
The neutron, discovered in 1932, turned out to be a powerful probe for studying the atom. When Enrico Fermi irradiated heavy atoms with neutrons, these were captured by the nuclei. New isotopes, often radioactive, were formed. In 1934 he and co-workers discovered that if the neutrons were slowed down, by e.g. paraffin shielding, the interaction rate with nuclei was increased, leading to discoveries of many hitherto unknown radioactive isotopes.