To improve the effective interactions in the $pf$ shell, it is important to measure the single-particle and single-hole states near the $N$ $=$ 28 shell gap. In this paper, the neutron spectroscopic factors of hole states from the unstable neutron-rich ${}^{45}$Ar ($Z$ $=$ 18,$N$ $=$ 27) nucleus have been studied using the ${}^1$H(${}^{46}$Ar,$d$) ${}^{45}$Ar transfer reaction in inverse kinematics. Comparison of our results with the particle states of ${}^{45}$Ar produced in ${}^2$H(${}^{44}$Ar, $p$) ${}^{45}$Ar reaction shows that the two reactions populate states with different angular momenta. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of ${}^{45}$Ar. These are the ground state ($f_{7/2}$), the first-excited state ($p_{3/2}$), and the $s_{1/2}$ and $d_{3/2}$ states. While large basis shell-model predictions describe spectroscopic properties of the ground and $p_{3/2}$ states very well, they fail to describe the $s_{1/2}$ and $d_{3/2}$ hole states.

• Received 5 October 2012

DOI:https://doi.org/10.1103/PhysRevC.88.017604