Fission barriers and half-lives of actinides in the quasimolecular shape valley

Abstract

The energy of actinide nuclei in the fusionlike deformation valley has been determined from a liquid drop model taking into account the proximity energy, the mass and charge asymmetries and the shell and pairing energies. Double-humped potential barriers appear. The saddle-point corresponds to the second maximum and to the transition from compact one-body shapes with a deep neck to two touching ellipsoids. The scission point, where the effects of the nuclear attractive forces between the fragments vanish, lies at the end of an energy plateau below the saddle-point and corresponds to two well separated fragments. The kinetic and excitation energies of the fragments come from the energy on this plateau. The shell and pairing effects play a main role to decide the most probable decay path. The heights of the potential barriers roughly agree with the experimental data and the calculated half-lives follow the trend of the experimental values. A shallow third minimum and a third peak appear in specific asymmetric exit channels where one fragment is close to a double magic quasi-spherical nucleus, while the other one evolves from oblate to prolate shapes.

Fission of actinides through quasimolecular shapes

“…The heights of the two peaks of the potential barriers roughly agree with the experimental data [9].…”

“…For shapes near the ground state the selected inertia is largely above the irrotational flow value since a large amount of internal reorganization occurs at level crossings [9]. For highly deformed shapes the reduced mass is reached asymptotically.…”

“…Within a Generalized Liquid Drop Model (GLDM) taking into account the mass and charge asymmetries, the proximity energy, and the shell and pairing energies, it has been demonstrated that there is a degeneracy between the energy of quasimolecular shapes and the energy of elongated shapes with a shallow neck. Most of the binary and ternary fission, and light nucleus emission and fusion properties have been also reproduced in this quasimolecular shape valley [5][6][7][8][9]. The purpose of this work is to investigate the actinide region remaining in this a e-mail: royer@subatech.in2p3.fr This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.…”

“…3). More generally, it has been proved that the potential barrier heights in this valley correspond precisely to the fission barrier heights [5][6][7][8][9].…”

Formation of superheavy elements in the capture of very heavy ions at high excitation energies

“…This macro-microscopic approach has been used to explore the data on the symmetric and asymmetric fission [9,10], α and light nucleus emission [11], fusion data [12,13] as well as the rotating highly deformed state characteristics [14].…”