Sub-barrier capture with quantum diffusion approach

V.V Sargsyan,N.V Antonenko,W Scheid,G.G Adamian,H.Q Zhang,R.A Kuzyakin

doi:10.1051/epjconf/20111704003

Abstract

With the quantum diffusion approach the behavior of capture cross sections and mean-square angular momenta of captured systems are revealed in the reactions with deformed and spherical nuclei at sub-barrier energies. With decreasing bombarding energy under the barrier the external turning point of the nucleus-nucleus potential leaves the region of short-range nuclear interaction and action of friction. Because of this change of the regime of interaction, an unexpected enhancement of the capture cross section is found at bombarding energies far below the Coulomb barrier. This effect is shown its worth in the dependence of mean-square angular momentum on the bombarding energy. From the comparison of calculated capture cross sections and experimental capture or fusion cross sections the importance of quasifission near the entrance channel is demonstrated for the actinidebased reactions and reactions with medium-heavy nuclei at extreme sub-barrier energies.

Highlights

From the comparison of capture cross sections and fusion cross sections one can show a significant role of the quasifission channel in the reactions with various mediumlight and heavy nuclei at sub-barrier energies
It worth remembering that first evidences of hindrance for compound nucleus formation in the reactions with massive nuclei at low energies near the Coulomb barrier were observed at GSI already long time ago [34]
By comparing the calculated and experimental capture cross sections one can study the importance of quasifission near the entrance channel for the actinide-based reactions leading to superheavy nuclei

Summary

Introduction

The measurement of excitation functions down to the extreme sub-barrier energy region is important for studying the long range behavior of nucleus-nucleus interaction as well as the coupling of relative motion with other degrees of freedom [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. From the comparison of capture cross sections and fusion cross sections one can show a significant role of the quasifission channel in the reactions with various mediumlight and heavy nuclei at sub-barrier energies. The competition between the complete fusion and quasifission can strongly reduce the value of the fusion cross section and, respectively, the value of the evaporation residue cross section [31,32,33]. This effect is especially crucial in the production of superheavy nuclei. It worth remembering that first evidences of hindrance for compound nucleus formation in the reactions with massive nuclei at low energies near the Coulomb barrier were observed at GSI already long time ago [34]

Comparison with experimental data and predictions

Th cap cap

Capture cross sections in reactions with large fraction of quasifission

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Summary