Fusion hindrance and synthesis of superheavy elements |
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Authors: | Y Abe G I Kosenko C W Shen B Bouriquet A Marchix D Boilley B Giraud |
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Institution: | (1) Research Center for Nuclear Physics, Osaka University, Ibaraki, Japan;(2) Department of Physics, Omsk University, Omsk, Russia;(3) School of Science, Huzhou Teachers College, China;(4) Center of Theoretical Nuclear Physics, National Laboratory of HIC, Lanzhou, China;(5) Department of Nuclear Physics, Australian National University, Canberra, Australia;(6) GANIL, Caen, France;(7) Service de Physique Théorique, CE-Saclay, Gif-sur-Yvette, France |
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Abstract: | A mechanism for fusion hindrance is clarified, based on the observation that the sticking configuration of projectile and
target is located outside of the conditional saddle point. Accordingly, the fusion process is described by two sequential
steps of passing over the Coulomb barrier and shape evolution toward the spherical compound nucleus. The latter one is indispensable
in massive systems. With the use of a two-step model, excitation functions of fusion reaction are calculated for various combinations
of projectiles and targets which lead to superheavy elements. The hindered fusion excitation measured is reproduced precisely
without any adjustable parameter. Combined with survival probabilities calculated by the statistical theory of decay, excitation
functions for residues of superheavy elements are calculated to compare with the systematic data measured for the cold fusion
path. The peak positions and the widths are correctly reproduced, though it is necessary to reduce the shell correction energies
of the compound nuclei predicted by the structure calculations in order to reproduce their absolute values. Predictions are
made for a few unknown heavier elements. Furthermore, a preliminary attempt toward the shell closure N = 184 is also presented using a neutron-rich secondary beam.
The text was submitted by the authors in English. |
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