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

Abstract

The properties of the low-lying states, especially the relevant shape coexistence in ${}^{80}$Ge close to one of most neutron-rich doubly magic nuclei at $N=50$ and $Z=28$ have been investigated within the framework of the proton-neutron interacting model (IBM-2). Based on the fact that the relative energy of the $d$ neutron boson is different from proton bosons', the calculated energy levels of low-lying states, $E2$ transition strengths can reproduce the experimental data very well. Particularly, the first excited state 0${}_2^{+}$ is reproduced quite nicely, which is intimately related with the shape coexistence phenomenon. And the ${\rho }^2(E0,0_2^{+}\to 0_1^{+})$ transition strength has been predicted. The experimental data and theoretical results indicate that both collective spherical and $\gamma$-soft vibration structures coexist in ${}^{80}$Ge. Key words: ${}^{80}$Ge, low-lying states, $E0$ transition strengths, shape coexistence, IBM-2.

Comments: 13 pages, 1 figure, accepted by Chinese Physics C