Abstract
After the synthesis of element 113, nihonium (Nh) via the 209Bi(70Zn,n)278Nh cold fusion reaction using the RIKEN heavy-ion Linear ACcelerator (RILAC) and the GAs-filled Recoil Ion Separator (GARIS), the search for the heaviest isotopes of oganesson was initiated with GARIS-II by means of the 248Cm(50Ti,xn)298−xOg fusion evaporation reaction. The optimal bombarding energy for the 50Ti + 248Cm reaction was determined from the quasielastic barrier distribution extracted from the excitation function of quasielastic backscattering. This method optimizes the compound nucleus formation. The search for Og was conducted for 39 days on the basis of the experimentally derived 50Ti beam energy of 227.9(5)MeV at the middle of 248Cm target. A precise analysis of the dataset based on multiple event search strategies revealed no decay chains with a total dose on 248Cm target of 4.93 × 1018 50Ti projectiles, reaching a sensitivity of 0.27pb and a 1σ upper cross section limit of 0.50pb.
| Original language | English |
|---|---|
| Article number | 094201 |
| Journal | Journal of the Physical Society of Japan |
| Volume | 94 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 2025 |
Funding
Acknowledgements The experiment was performed at the Radioactive Ion Beam Factory operated by RIKEN Nishina Center for Accelerator-Based Science and Center for Nuclear Study, University of Tokyo. We are grateful to N. Sakamoto, T. Nakagawa, and M. Kidera for providing excellent 50Ti beams by operating the 18-GHz ECR ion-source and the RILAC accelerator. We are also very grateful to the staff of the RILAC accelerator group through their collaborative work. The GARIS II recoil separator was supported by a Grant-in-Aid for Specially Promoted Research, 19002005, 2007, from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The 248Cm isotope used in this research was supplied by the U.S. Department of Energy (DOE) isotope program, managed by the Office of Isotope R&D and Production. ORNL is managed by UT-Battelle, LLC under DOE Contract No. DE-AC05-00OR22725. We are very grateful to T. Cap for sharing with us the results of his very recent calculations as a private communication and for all the very constructive and helpful comments. Finally, we would like to thank H. En’yo who was Director of the RNC during the experiment for promoting the SHE search program. Without his continuous support and encouragement, this experiment could not have been realized. We also thank present RNC Director H. Sakurai for his support for the nSHE experiments as a continuation of the present experiment. The experiment was performed at the Radioactive Ion Beam Factory operated by RIKEN Nishina Center for Accelerator-Based Science and Center for Nuclear Study, University of Tokyo. We are grateful to N. Sakamoto, T. Nakagawa, and M. Kidera for providing excellent 50Ti beams by operating the 18-GHz ECR ion-source and the RILAC accelerator. We are also very grateful to the staff of the RILAC accelerator group through their collaborative work. The GARIS II recoil separator was supported by a Grant-in-Aid for Specially Promoted Research, 19002005, 2007, from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The 248Cm isotope used in this research was supplied by the U.S. Department of Energy (DOE) isotope program, managed by the Office of Isotope R&D and Production. ORNL is managed by UT-Battelle, LLC under DOE Contract No. DE-AC05-00OR22725. We are very grateful to T. Cap for sharing with us the results of his very recent calculations as a private communication and for all the very constructive and helpful comments.