Shell model description of the core excited level structure of $^{89}$Sr nucleus and systematic features of the $N=51$ odd-A isotones

Abstract

Shell-model calculations are performed using NuShellX code in the model space $\pi$($f_{5/2}$, $p_{3/2}$, $p_{1/2}$, $g_{9/2}$) $\otimes$ $\nu$($g_{9/2}$, $g_{7/2}$, $d_{5/2}$, $h_{11/2}$), which probe the proton core excitation from the interior of $Z=38$ semiclosed shell and neutron core excitation from the interior of $N=56$ semiclosed shell for the level structure of $^{89}$Sr. Our calculations show that the excitation of a single $d_{5/2}$ neutron across $N=56$ semiclosed shell into the $h_{11/2}$ orbit should have great effects on the excited states of $^{89}$Sr. In addition, the systematic features of proton core excitation across $Z=38$ semiclosed shell into the $g_{9/2}$ orbit and neutron core excitation across $N=56$ semiclosed shell into the $g_{7/2}$, $s_{1/2}$, $d_{3/2}$, $h_{11/2}$ orbits in $N=51$ isotones are discussed.