Radioactive-Ion Beams for the Fission Study of Heavy Neutron-Rich Nuclei
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NUCLEI Experiment
Radioactive-Ion Beams for the Fission Study of Heavy Neutron-Rich Nuclei G. M. Ter-Akopian1), 2)* , Yu. Ts. Oganessian1), 2) , A. A. Bezbakh1) , A. S. Fomichev1), 2) , M. S. Golovkov1), 2) , A. V. Gorshkov1), S. A. Krupko1), E. Yu. Nikolskii1), 3) , S. I. Sidorchuk1), S. V. Stepantsov1) , and R. Wolski1), 4) Received Deсember 25, 2019; revised Deсember 25, 2019; accepted Deсember 25, 2019
Abstract—Quasi-elastic, multi-nucleon transfer reactions induced by the radioactive-ion beams with energy 4–6 MeV/u allow one to produce moderately excited neutron-rich nuclei with atomic numbers 95 < Z < 110. This offers a new approach to the study of the so far unknown nuclei in the neighborhood of the recently discovered island of super-heavy elements and to the acquirement of new data specifying significant fission characteristics of the actinide nuclei appearing in the r-process nucleosythesis. DOI: 10.1134/S1063778820040195
1. INTRODUCTION The experimental ascertainment of the existence of nuclides with atomic numbers extending up to Z = 118 signifies the discovery of the super-heavy elements (SHEs) [1, 2]. This heightens interest to the advance towards the positions on the nuclide map where the nuclei with neutron numbers around N = 162 and those going up to N > 170 are located. In this context, feasible ways to obtain such nuclei produced in the heavy-ion fusion reactions, followed by the proton and α-particle evaporation, have been considered [3]. The possible production of the unknown, heavier-mass SHE isotopes in multi-nucleon transfer (MNT) reactions induced by the heavy-ion beams was the discussion subject [4–6]. The reason for this interest is caused by the importance of receiving the experimental data needed to learn more about the properties of nuclei lying closer to the center of the SHE stability island. Another compelling reason for getting such information about even broader group of actinide nuclei, lying on the way to the magic neutron numbers N = 162 and 184, originates from the topical theme of the r-process nucleosynthesis. It was assumed long ago [7] that the spontaneous fission of 254 Cf was the source of energy deposit causing the long lasting light emission from the typeIa supernovae. Close attention to this subject arose
after the discovery of gravitational waves coming from the GW170817 neutron star merger [8] and the observation of possible signs of heavy-element nucleosynthesis in the late-time emission of light coming from that event [9, 10]. There are reasons for supposing [11] that such mergers are the dominant rprocess sites in the Universe. The analyses made on the possible effects caused by the neutron-induced and beta-delayed fission [12] show that (along with the atomic masses and β-decay strength functions) the fission barriers of Z = 90–102 and N = 160– 184 nuclei define greatly the yields of actinide nuclei obtainable in the r process. Thus, one sees that the measurements of the fission barriers performed for the so far unknown actinide and trans-actinide nuclei being shifted b
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