Structure of odd-odd Cs isotopes within the interacting boson-fermion-fermion model based on the Gogny-D1M energy density functional

Abstract

The spectroscopic properties of the odd-odd isotopes 124−132 Cs have been studied within the interacting boson-fermion-fermion model based on the Gogny-D1M energy density functional framework. Major ingredients to build the interacting boson-fermion-fermion Hamiltonian, such as the (β, γ)-deformation energy surfaces for the even-even core nuclei 124−132 Xe as well as single-particle energies and occupation probabilities of the odd nucleons, have been computed microscopically with the constrained Hartree-Fock-Bogoliubov method. A few coupling constants of the boson-fermion and residual neutron-proton interactions are fitted to reproduce with a reasonable accuracy the experimental excitation energy of the low-lying levels of the odd-mass and odd-odd nuclei. The method is applied to describe the low-energy low-spin spectra of the odd-odd Cs nuclei and the band structures of higher-spin higher-energy states, mainly based on the νh 11/2 ⊗ (πh 11/2 ) −1 configuration. The nucleus 128 Cs, has been identified as the best candidate for exhibiting chiral doublet bands.

$β$ decay of even-A nuclei within the interacting boson model based on nuclear density functional theory

“…The low-lying level structure and electromagnetic properties of the even-even Ba and Xe, as well as oddodd Cs, nuclei have already been discussed in detail in Ref. [36]. Also in this reference, the IBFM description of the neighboring odd-N Ba and Xe as well as odd-Z Cs isotopes has been amply discussed and shown to be also in reasonable agreement with experiment.…”

“…Other spectroscopic properties of the low-lying states of the even-even Xe and Ba and odd-odd Cs isotopes, such as the electric quadrupole and magnetic dipole moments and transition strengths, were described reasonably well [36]. Cs(0 + 1 ) →Xe(0 + 1 ) Ba(0 + 1 ) →Cs(0 + 1 )…”

“…The employed boson-fermion interaction strengths, and jρ and v 2 jρ for the odd-odd Cs nuclei can be found in Ref. [36]. Finally, the strength parameters for the residual neutron-proton interaction, u D = 0.7 MeV and u T = 0.02 MeV, are taken also from Ref.…”

“…Therefore, the low-energy spectra of the odd-odd Cs nuclei are described in terms of an unpaired neutron hole and a proton coupled to the γ-soft even-even core Xe nuclei. The low-energy positive-parity states of the oddodd Cs nuclei, with excitation energies typically up to E exc ≈ 0.4 MeV, have been shown [36] to be built on the (νsdg) −1 ⊗ (πsdg) 1 neutron-proton pair configuration.…”

Transfer reactions between odd-odd and even-even nuclei by using IBFFM

“…In a second more general approach, which we will follow in this paper, the Interacting Boson Model (IBM) was extended to describe odd-odd nuclei, in which the two fermions (one neutron and one proton) are coupled to the even-even core described either by IBM-1 [11][12][13], or by IBM-2 [14,15]. These extensions to odd-odd nuclei are usually referred to as the Interacting Boson-Fermion-Fermion Model, IBFFM-1 and IBFFM-2, respectively.…”