The 40th Anniversary of the Discovery of Americium and Curium

Abstract

The recognition, in July 1944, that the unknown elements with atomic numbers 95 and 96 should be members of an actinide transition series was the key to their chemical identification following nuclear synthesis, i.e., the breakthrough that led to their discovery. That same month ²³⁹Pu was bombarded with 32 MeV helium ions in the Berkeley 60-Inch Cyclotron and sent to the wartime Metallurgical Laboratory in Chicago where chemical separations led to the identification of ²⁴²96, produced in the reaction ²³⁹Pu (α,n) Neutron bombardments of ²³⁹Pu in the reactors at Clinton Laboratories, Tennessee, and the Hanford Engineer Works, Washington, followed by chemical separations in Chicago, led to the identification, completed in January 1945, of ²⁴⁰95 and ²⁴²96 (again), produced by the reactions ²³⁹Pu (n,γ) ²⁴⁰Pu (n,γ) $^{241}Pu{\text{ }}{\xrightarrow{{{\beta ^ - }}}^{241}}95{(N,\gamma )^{242}}{95_{\xrightarrow{{{\beta ^ - }}}}}^{242}96.$ The names americium (95) and curium (96) were suggested at an ACS annual Spring Meeting in April, 1946.