Bonn 2010 – wissenschaftliches Programm
HK 15.2: Vortrag
Dienstag, 16. März 2010, 14:15–14:30, HG II
Observation of element 114 at LBNL — •Jan Dvorak1,2, Liv Stavsetra1, Kenneth. E. Gregorich1, Paul A. Ellison1,2, Irena Dragojevic1,2, Mitch A. Garcia1,2, and Heino Nitsche1,2 — 1Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA — 2Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA
We report on the first independent verification of element 114 at Lawrence Berkeley National Laboratory (LBNL). In the past years the Dubna Gas Filled Recoil Separator (DGFRS) group reported the successful synthesis of superheavy elements (SHE) in numerous 48Ca irradiations of actinide targets. Cross sections reported from these experiments are remaining rather constant at the level of a few picobarns, breaking the strong downward trend obvious in hot fusion reactions with other projectiles. Verification of the DGFRS results hence is of paramount importance, but for a long time, confirmation attempts failed to produce SHE in 48Ca induced reactions. In a 8-day experiment at the Berkeley Gas-filled Separator (BGS) at LBNL we have observed production of two atoms of element 114 in the reaction 48Ca(242Pu,3-4n)287,286114. Based on the observed decay properties these decay chains were attributed to the decay of 287114 and 286114 produced in the 3n and 4n channel, respectively. Decay modes, lifetimes, and decay energies are consistent with those reported by the DGFRS group. The 1.4 pb cross sections measured in this work for both the 3n and 4n channels are lower than 3.6 pb and 4.5 pb, respectively, reported by the DGFRS group.