Sequence of consecutive alpha-decays from Element 113
The search for "superheavy elements", unstable synthetic elements with extremely short half-lives, is a difficult and painstaking process. Such elements do not occur in nature and must be produced through experiments involving nuclear reactors or particle accelerators, via processes of nuclear fusion or neutron absorption. Since the first such element, neptunium (Np) with atomic number 93, was discovered through synthesis in 1940, the US, Russia, and Germany have competed to synthesize more of them. Elements 93 to 103 were discovered by the Americans, elements 104 to 106 by the Russians, and elements 107 to 112 by the Germans.
Japan joined the race in 2004, with its synthesis of element 113. The discovery was made by the Superheavy Element Laboratory, headed by Associate Chief Scientist Dr. Kosuke Morita. Using the RIken LineAC (RILAC) linear accelerator and a novel nuclei separator, called the gas-filled recoil separator (GARIS), the group generated element 113 on the night of July 23, after years of research and preparation. The discovery was made possible thanks to the high performance capacity of RILAC and the careful selection of optimal incident energy for the beam nuclei.
The name of "Japonium" has been tentatively proposed for the new element, whose temporary name is Ununtrium (Uut). A Russian team, who published results on the synthesis of element 115 in February 2004, has reported the production of element 113 as a byproduct, and thus claims to have produced element 113 first. However, only the Japanese team has been able to trace back the chain of decay and prove, on an experimental basis, the atomic and mass numbers of the synthesized element.