SUPERHEAVY ELEMENTS — SYNTHESIS, STRUCTURE AND REACTION MECHANISM

Abstract

The elements with Z = 107 - 112 have been successfully synthesized at GSI employing 208 Pb and 209 Bi targets and producing relatively cold compound systems. The unambiguous identification of these elements via evaporation residue(ER)-α correlations and the link to known α emitters has been confirmed by independent measurements performed at RIKEN, Japan and partly by chemistry experiments. An impressive body of data which is interpreted as the synthesis of isotopes with Z = 114 - 116 and 118 has been accumulated at the FLNR, Dubna, where the alternative approach of reactions with actinoide targets forming more excited compound nuclei was pursued. Despite of a consistent systematic picture, the final confirmation, however, is still missing. These exciting results together with the possibilities opened up by the advanced experimental techniques and the nowadays available beam intensities with their expected future increase have triggered a broad range of activities. Apart from experiments to attempt the synthesis of new elements, nuclear structure investigations in the transactinoide region has become possible for Z up to 108 or 110. Heavy element chemistry has successfully placed Hs in the periodic table and is now attacking element 112. The development of accelerators and experimental methods promises advances to enable the extension of these investigations in regions closer to the "island of stability". Mass measurements using ion traps and neutron rich unstable beam species for the systematic investigation of nuclear structure and reaction mechanisms for heavy neutron rich systems are believed to complete the variety of tools in future.