Fission barriers of two odd-neutron actinide nuclei taking into account the time-reversal symmetry breaking at the mean-field level

Abstract

Background: Fission barriers of actinide nuclei have been mostly and for long been microscopically calculated for even-even fissioning systems. Calculations in the case of odd nuclei have been performed merely within a so-called equal-filling approximation (EFA) as opposed to an approach taking explicitly into account the time reversal breaking properties at the mean field level-and for only one single-particle configuration. Purpose: We study the dependence of the fission barriers on various relevant configurations (e.g. to evaluate the so-called specialization energy). Besides, we want to assess the relevance as a function of the deformation of the EFA approach which has been already found out at ground state deformation. Methods: Calculations within the Hartree-Fock plus BCS with self-consistent particle blocking have been performed using the SkM* Skyrme effective interaction in the particle-hole channel and a seniority force in the particle-particle channel. Axial symmetry has been imposed throughout the whole fission path while the intrinsic parity symmetry has been allowed to be broken in the outer fission barrier region. Results: Potential energy curves have been determined for six different configurations in 235 U and four in 239 Pu. Inner and outer fission barriers have been calculated along with some spectroscopic properties in the fission isomeric well. These results have been compared with available data. The influence of time-reversal breaking mean fields on the solutions has been investigated. Conclusions: A sizeable configuration dependence of the fission barrier (width and height) has been demonstrated. A reasonable agreement with available systematic evaluations of fission barrier heights has been found. The EFA approach has been validated at the large elongations occurring at the outer barrier region.

Jost function formalism based on the Hartree-Fock-Bogoliubov formalism

“…The pairing correlation in nuclei is very important to explain the fundamental properties of nuclei, such as the magic number, the separation energy and the quadrupole 1st excited state of nucleus, and so on. In the last decades, the investigation of the pairing effect on nuclear structure has been held based on the microscopic theoretical framework, such as the Hartree-Fock-Bardeen-Cooper-Schrieffer (HF+BCS) [29], the Hartree-Fock-Bogoliubov (HFB) [30], the Highly Truncated Diagonalization Approach (HTDA) [31,32] and the Quasiparticle Random Phase Approximation (QRPA) [33][34][35][36]. Di-neutron correlation resulting from the coherent overlap of the continuum states due to the pair correlation at both ground state and the low-lying excitation of the neutron drip line nuclei has been discussed [36].…”

Single-Particle Spectra, Pairing Correlations and Spectroscopic Properties of Actinide and Heavier Nuclei

“…Calculations performed with three Skyrme force parametrizations SIII, SkM * and SLy5 * [18] have actually yielded similar conclusions (see Refs. [19,20] for such spectroscopic properties in the second well of odd fissioning systems).…”

100 years of nuclear isomers—then and now

“…4 for comparison with K-isomer decay by A c c e p t e d M a n u s c r i p t tunnelling through the γ degree of freedom. Fission isomer properties, including half-lives, are broadly understood in terms of the underlying shell structure [71,72,73,74], with new advances for odd-A nuclides [75]. A recent experiment identified a T 1/2 = 3.6 ms fission isomer in 235 U for the first time [76].…”