Excited $0^{+}$ states in ${}^{62}$Zn populated via the ${}^{64}$Zn($p$,$t$)${}^{62}$Zn reaction

A search for excited $0^{+}$ states in ${}^{62}$Zn was conducted via the ${}^{64}$Zn($p,t$)${}^{62}$Zn reaction. Four such states in ${}^{62}$Zn were observed up to an excitation energy of 5.4 MeV. The measured angular distribution for the previously assigned $0_2^{+}$ state at 2342 keV is consistent with a $2^{+}$ assignment, and thus the first excited $0^{+}$ state is now assigned at 3043 keV. Due to the energy scaling in the currently adopted formalism for isospin-mixing corrections in superallowed Fermi $\beta$ decay, ${\delta }_{C1}$ for ${}^{62}$Ga is reduced by nearly a factor of two. This result shifts the theoretical value closer to previous experimental determinations of the same quantity through ${}^{62}$Ga superallowed $\beta$-decay branching-ratio measurements.

Figure 1

Experimental angular distributions for the five observed $0^{+}$ states in ${}^{62}$Zn from this work. The data are compared to one-+two-step DWBA calculations using shell-model wave functions for each respective final state, and in most cases the experimental uncertainties are smaller than the data points. Due to the large cross-section disparity between the ground state and the excited states, the $0_1^{+}$ state is displayed on a different scale. The curves are normalized to the data in order to provide a better shape comparison. A discussion on the assignment of each state and a comparison with previous experimental data are given in the text.

Figure 2

(a) Experimental angular-distribution data for the 2342-keV state, shown with calculated DWBA prediction for $L=0$ and $L=2$ transfers. With the exception of the ${10}^{\circ }$ cross section, the 2342-keV state exhibits a nearly identical angular-distribution shape to the well-known 954-keV $2_1^{+}$ state, shown in panel (b) for comparison. The focal-plane position spectrum region of interest for the respective states at ${30}^{\circ }$ are displayed as an inset in the top right corner, where the listed energies are in keV. The assignment of the 2342-keV state is discussed further in the text.