NEW RESULTS FOR ELEMENTS 115,117,AND 118 PRODUCED IN THE REACTIONS ~(243)Am+~(48)Ca AND ~(249)Bk/~(249)Cf+~(48)Ca

摘要

The reactions of ~(243)Am and ~(249)Bk with ~(48)Ca have been reinvestigated to provide new evidence for the discovery of elements 113, 115,and 117. Three isotopes ~(287-289)115 were synthesized in the ~(243)Am+~(48)Ca reactions at five projectile energies, providing excitation functions and a-decay spectra of the produced isotopes. Decay properties of ~(287,288)115 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time. The new~(289)115 events demonstrate the same decay properties as those observed for ~(289)115 populated by a decay of ~(293)117 produced in the ~(249)Bk+~(48)Ca reaction to provide cross-bombardment evidence. Results of recent experiments at the Dubna gas-filled recoil separator aimed at studying production cross-sections, excitation functions, and nuclear decay properties for isotopes ~(293,294)1 17 synthesized in the ~(249)Bk+~(48)Ca reaction at five projectile energies are presented. In addition, a single decay of ~(294)118 was observed from the reaction with ~(249)Cf - a result of the in-growth of ~(249)Cf in the ~(249)Bk target.