On current ambiguity in the interpretation of fission at intermediate excitation energy

Abstract

Various approaches are currently used to interpret experimental data on fission. We critically examine a wide set of observables measured for fission $^{206,210}$Po nuclei at medium excitation energy, and illustrate the ambiguity in current analysis. Dynamical calculations based on the four-dimensional Langevin equation using a macroscopic potential energy landscape are performed, and found to consistently describe available measurements. This observation calls into question the robustness of recent analysis based on statistical-model calculations and concluding, on the contrary, to substantial shell effects at the fission saddle point $^{206-210}$Po. The inconsistency in interpretation reached by the two approaches shows that, depending on the system, the conclusion can be strongly model-dependent. Although this may not be surprising, it emphasizes the today still limited reliability of firmly extracting fundamental nuclear properties from customary analysis

Probing nuclear dissipation via evaporation residue excitation functions for theO16,18+Pt198reaction

“…The best-fit dissipation strengths lie in the ranges (0-1) x 1021 s_l and (0.5-1.5) x 1021 s " 'for the compound nuclei 2,4Rn and 2l6Rn respectively. In a recent multidimensional Langevin dynamical calculation including the orientation degree of freedom, reasonable agreement with 044621-7 experimental observables is obtained for the compound nuclei 206.2i0po [44] xhe chaos-weighted one-body dissipation from Ref. [45] used in this work is shape dependent and varies in the range (0-3) x 1021 s_l between the ground state and the saddle configuration.…”

No influence of aN=126neutron-shell closure in fission-fragment mass distributions

“…The role of nuclear shell effects on various nuclear reaction processes as a function of excitation energy, specially for the nuclei around the shell closure, has currently remained an issue of intense discussions [1][2][3][4][5][6][7][8][9]. Apart from the basic understanding point of view, a large part of the recent activities were concentrated on the study of shell effect in fission of heavy nuclei with the aim to unveil the relationship between nuclear structure and nuclear stability.…”

Influence of fusion dynamics on fission observables: A multidimensional analysis

“…Accordingly, a robust understanding has not been reached yet, and various interpretations of the same experimental data exist (see Refs. [3][4][5] and therein). Even under "clean" conditions, satisfying Bohr's hypothesis about the independence of the decay of the excited system on the way it was produced, inconsistencies are found (see the discussion in Ref.…”