Speaker
Description
The production of a superheavy element in a fusion heavy-ion reaction schematically proceeds through the three stages: (i) the two colliding nuclei overcome the Coulomb repulsion and come in contact, (ii) the contact configuration evolves into a compact shape, (iii) the fused nucleus cools down by neutron evaporation. In the present presentation the second step is described in a new method [1], utilising the Langevin equation and random walk models. The two fragments come in contact with a large kinetic energy that is subject to dissipation and is transferred into heat. The dissipation process is described by the Langevin equation, where the friction strength depends on the necking of the combined object (window friction), and is characterised by drift-dominated dynamics in the center-of-mass direction. With no remaining kinetic energy several shape degrees of freedom can be explored, and the dynamics becomes diffusion dominated. The dynamics in five shape degrees of freedom is treated as Metropolis random walks, and if the inner saddle is crossed a fusion event has taken place. Quasi-fission competes with fusion events, and we count the relative number of fusion events, constituting a formation probability. The walks are controlled by calculated angular momentum dependent potential energies as well as pairing and shell-energy dependent level-densities in a large grid in deformation space, implying the fusion dynamics depends on temperature, pairing and shell structure.
[1] M. Albertsson, B.G. Carlsson, T. Døssing, J. Randrup, D. Rudolph, and
S. Åberg, Phys. Rev. C 110, 014624 (2024).
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| Are you a student or postdoc? | no |
