Spherical-like spectra for the description of the normal states of $^{108-120}$Cd in the SU3-IBM and the $Q_{2_{1}^{+}}$ anomaly

Abstract

The Cd puzzle implies that the phonon excitation of a spherical nucleus should be questioned and refuted. For understanding this spherical-like $\gamma$-soft mode newly found experimentally, a possible answer was proposed recently in the SU3-IBM. In this paper, the evolutions of the normal states in $^{108-120}$Cd are investigated and compared with the experimental results. For better explaining the nearly zero B(E2) values between the $0_{2}^{+}$ state and the $2_{1}^{+}$ state, except for the SU(3) second-order and third-order Casimir operators, other SU(3) higher-order interactions are also considered in detail. It can be found that the results of theoretical fitting and experimental data agree well with simple parameter selection. The spherical-like spectra really exist. The deficiency may come from the lack of configuration mixing. The realistic spectra characteristics of the spherical-like spectra are found for $^{118,120}$Cd and the electric quadrupole moments of the $2_{1}^{+}$ state are predicted. The $Q_{2_{1}^{+}}$ anomaly in $^{108-116}$Cd are also discussed.