Synthesis of heavy and superheavy elements

Abstract

In two series of experiments at SHIP, six new elements (Z = 107–112) were synthesized via fusion reactions using lead or bismuth targets and 1n-deexcitation channels. The isotopes were unambiguously identified by means of α-α correlations. Not fission, but alpha decay is the dominant decay mode. Cross-sections decrease by two orders of magnitude from bohrium (Z = 107) to element 112, for which a cross-section of 1 pb was measured. Based on our results, it is likely that the production of isotopes of element 114 close to the island of sphericalSuperHeavy Elements (SHE) could be achieved by fusion reactions using208Pb targets. Systematic studies of the reaction cross-sections indicate that the transfer of nucleons is an important process for the initiation of fusion. The data allow for the fixing of a narrow energy window for the production of SHE using 1n-emission channels. The likelihood of broadening the energy window by investigation of radiative capture reactions, use of neutron deficient projectile isotopes and use of actinide targets is discussed.