Probing collectivity in Zn isotopes with one particle or hole outside the $N=40$ subshell closure

The nuclear structure of the odd-mass ${}^{69}\mathrm{Zn}$ and ${}^{71}\mathrm{Zn}$ isotopes, with one hole or one particle outside the $N=40$ subshell closure, has been investigated by measuring the lifetime of excited states using the recoil distance Doppler-shift method. The nuclei of interest were produced in a deep-inelastic reaction in inverse kinematics with a ${}^{238}\mathrm{U}$ beam impinging on a ${}^{70}\mathrm{Zn}$ target. Single-particle and collective states were found to coexist at low energy in ${}^{69}\mathrm{Zn}$ and ${}^{71}\mathrm{Zn}$.

Figure 1

$\gamma$-ray spectrum of ${}^{69}\mathrm{Zn}$. The shifted components are indicated with a $♠$ symbol, unshifted with $⧫$, while unknown transitions are indicated with $*$.

Figure 2

Partial level scheme, extracted from the known ${}^{69}\mathrm{Zn}$ level scheme [25], showing the observed $\gamma$-ray transitions.

Figure 3

$\gamma$-ray spectrum of ${}^{69}\mathrm{Zn}$ showing the evolution of the shifted ($♠$) and unshifted ($⧫$) components of the unassigned transition at 1108.7(11) keV as a function of target-degrader distance: 34 $\mu \text{m}$ (a) and 99 $\mu \text{m}$ (b).

Figure 4

$\gamma$-ray spectrum of ${}^{71}\mathrm{Zn}$. The shifted components are indicated with a $♠$ symbol, unshifted with $⧫$, while unknown transitions are indicated with $*$.

Figure 5

Partial level scheme of ${}^{71}\mathrm{Zn}$ showing the identified $\gamma$-ray transitions observed in the present study according to the known ${}^{71}\mathrm{Zn}$ level scheme [26].