New γ-soft rotation in the interacting boson model with SU(3) higher-order interactions *

Abstract

The interacting boson model with SU(3) higher-order interactions offers a new route to enlarge our understanding on γ-soft rotation. In this paper, U(5)-like and O(6)-like new γ-softness are found, in which the corresponding energy levels in the ground band and the quasi-γ band can be exactly degenerate, and have a partial O(5) dynamical symmetry. The spherical-like γ-softness is not related to the classical O(6) dynamical symmetry. The transitional behaviors of B(E2) values of the low-lying levels, and quadrupole moment of the 2+ 1 state are also discussed. Spherical-like γ-softness can be used to explain the low-lying spectra and B(E2) values in 110 Cd normal states.

$E(5)$-like emerging $γ$-softness in $^{82}$Kr

“…On the other hand, it is found that the SU3-IBM can be also used to describe the asymmetric prolate-oblate shape phase transition in the Hf-Hg region [49]. The belief that triaxiality results from the competition between the prolate shape and the oblates shape [32] is further exemplified, which is also discussed in the Xe-Ba region recently [50].…”

“…The Hamiltonian supporting the new γ-softness was proposed in [32], which is composed of two parts. One is the d-boson number operator nd of the U (5) limit.…”

“…These novel results [30,31] encourage us to understand the existing experimental phenomena from a new perspective. The interacting bosom model with SU (3) higher-order interactions (SU3-IBM) was proposed by one of the authors, in which the algebraic Hamiltonian is constructed with only considering the U (5) limit and the SU (3) limit [32]. Various quadrupole deformations including the γ-rigid triaxiality can be described in this SU (3) limit, and the combination with the U (5) limit can induce the emergence of the γ-softness.…”

“…The new γ-softness was found to be intimately related with realistic γ-soft nuclei. For example, the normal states of 110 Cd is newly certified that can be described by the new γ-soft rotational mode [32], which is related to the spherical nucleus puzzle [33][34][35][36][37][38][39][40][41]. And it is also found that this emerging γ-softness can describe the properties of 196 Pt [42].…”

“…The γ-softness discussed in the simplest SU3-IBM has one specific feature [32] that the energy of the 0 + 3 state is nearly twice the one of the 0 + 2 state. Thus the 0 + 2 and 0 + 3 states can not be close to each other, which is the major drawback when fitting the γ-soft nucleus 196 Pt.…”