The synthesis of heavy nuclei has fundamental interest for nuclear physics. The heaviest elements provide an excellent laboratory for the understanding of nuclear structure in a strong Coulomb field. For over twenty-five years experimentalists sought to synthesize super-heavy nuclei at or near the region of spherical shell closure at Z=114 and N=184, although some modern Hartree-Fock and Mean-Field calculations predict that the region of increased stability is located near Z=120 or Z=126. The unambiguous synthesis of the elements 110-112 at GSI has proven difficult to proceed beyond using the so-called "cold fusion" approach of bombarding lead or bismuth target atoms to produce heavy compound nuclei at low excitation energy.
Recent calculations of R. Smolanczuk indicated a dramatic increase in the production cross section of element 118 in the reaction 208Pb(86Kr,1n)293118X. We have studied this reaction at the 88-inch cyclotron of the Lawrence Berkeley National Laboratory using the Berkeley gas-filled separator. In two experiments, three alpha-decay chains were observed that could be interpreted as a decay of element 118.
A new interpretation of existing data, the importance of shell closures between the interacting partners as well as viability of the "cold fusion" approach will be discussed. The idea of a fusion process, where only the fission-barrier properties of the compound system seem to be the determining factor of the amalgamation will be presented.
ANL Physics Division Colloquium Schedule