Dominant $(g_{9/2}){}^2$ neutron configuration in the $4_1^{+}$ state of ${}^{68}\mathrm{Zn}$ based on new g factor measurements

The g factor of the $4_1^{+}$ state in ${}^{68}\mathrm{Zn}$ was remeasured with improved energy resolution of the detectors used. The value obtained is consistent with the previous result of a negative g factor, thus confirming the dominant $0g_{9/2}$ neutron nature of the $4_1^{+}$ state. In addition, the accuracy of the g factors of the $2_1^{+},2_2^{+}$, and $3_1^{-}$ states has been improved and their lifetimes were well reproduced. New large-scale shell-model calculations based on a ${}^{56}\mathrm{Ni}$ core and a $0f_{5/2}1p0g_{9/2}$ model space yield a theoretical value, $g(4_1^{+})=+0.008$. Although the calculated value is small, it cannot fully explain the experimental value, $g(4_1^{+})=-0.37(17)$. The magnitude of the deduced $B(E2)$ of the $4_1^{+}$ and $2_1^{+}$ transitions is, however, rather well described. These results demonstrate again the importance of g factor measurements for nuclear structure determinations because of their specific sensitivity to detailed proton and neutron components in the nuclear wave functions.

Figure 1

Level scheme of ${}^{68}\mathrm{Zn}$ with γ transitions relevant to the present work.

Figure 2

Relevant γ-coincidence spectrum of a Ge detector placed at ${\Theta }_{\gamma }={65}^{°}$ relative to the beam axis. The Doppler-broadened lineshapes reflect the nuclear lifetimes.

Figure 3

Comparison of experimental g factors associated with the $2_1^{+},4_1^{+}$, and $2_2^{+}$ states in ${}^{64}\mathrm{Zn}$ and ${}^{68}\mathrm{Zn}$ (closed circles) with results from large-scale shell-model calculations (crosses; see text). Lines are drawn to guide the eye.