Coexistence of Prolate and Oblate Shapes in ⁹⁸ Sr Nuclei Using IBM2

Abstract

The properties of the low-lying states and the shape coexistence in 98 Sr are investigated within the framework of the proton-neutron interacting boson model (IBM2). By considering the relative energy of the 𝑑 proton boson to be different from that of the neutron boson, it is found that the calculated energy levels and the 𝐵(𝐸2) transition strengths agree with the experimental data perfectly. Particularly, the second 0 + state, which is associated with the shape coexistence phenomenon and has the lowest energy 𝐸(0 +2 ) among all known even-even nuclei, is reproduced very well. The behavior of the calculated quadrupole shape invariants is consistent with the experimental results.

Shape coexistence close to N = 50 in the neutron-rich isotope 80 Ge investigated by IBM-2

“…The reason is that the proton-neutron pairing effects cannot be neglected in this case. The IBM-2 without introducing configuration mixing has been used to investigate shape coexistence in some nuclei in the A ∼ 100 mass region [36,37], and in the neutron-deficient isotopes 74,76 Kr [38]. The numerical calculations are in good agreement with the recent experimental values for the low-lying energy spectrum, and the key sensitive quantities such as the quadrupole shape invariants and the B(E2) transition strength branch ratios.…”

Shape coexistence close to $N=50$ in the neutron-rich isotope $^{80}$Ge investigated by IBM-2

“…However, their calculated energy levels of the states E(0 + 2 ) and E(2 + 2 ) are a little higher than the experimental data especially for 80 Ge, the reason is that the proton-neutron pairing effects could not be neglected in this case. On the other hand, the IBM-2 without introducing the configuration mixing has been used to investigate shape coexistence in some nuclei in the A ∼ 100 mass region [36,37], and in the neutron-deficient isotopes 74,76 Kr [38]. The numerical calculations are in good agreement with the recent experimental values for the low-lying energy spectrum, and the key sensitive quantities such as the quadrupole shape invariants and the B(E2) transition strength branch ratios.…”

Shape coexistence in 76Se within the neutron–proton interacting boson model

“…K Nomura et al studied the structural evolution in selenium nuclei by means of the mapped IBM based on the Gogny energy density functional [2]. In this paper, we extend our previous studies of IBM-2 on the shape coexistence to 76 Se nucleus [31][32][33][34][35][36][37][38][39][40][41], and extract the associated signatures of shape coexistence by analyzing the lowlying level scheme and M1 transition transition rates in addition to E2 transitons. We expect to improve the description of + 0 2 state in the framework of IBM-2 which is important for the shape coexistence.…”