Enrico Fermi's Discovery of Neutron-Induced Artificial Radioactivity:The Influence of His Theory of Beta Decay

We analyze the influence of Enrico Fermi's theory of beta decay, which he formulated in December 1933, on his experimental discovery of neutron-induced artificial radioactivity four months later, in March 1934.We discuss Gian Carlo Wick's application of Fermi's theory in interpreting Frédéric Joliot and Irène Curie's discovery of alpha-particle-induced artificial radioactivity, and how Fermi was then influenced by his theory in planning his neutron-bombardment experiments, in his decision to use a radon-beryllium (Rn-Be) neutron source, and in his choice of the elements he bombarded with Rn-Be neutrons. Our analysis is based crucially on Fermi's first laboratory notebook, the Hirpine Notebook, which is preserved in the Oscar D'Agostino Archives in the Technical Institute "Oscar D'Agostino" in Avellino, Italy, and on the materials that are preserved in the Fermi Archives in the Domus Galilaeana in Pisa. These documents enable us to reconstruct Fermi's discovery of neutron-induced artificial radioactivity and to assign an exact date to it of March 20, 1934.