Search for the $^{73}\mathrm{Ga}$ ground-state doublet splitting in the $\beta$ decay of $^{73}\mathrm{Zn}$

The existence of two close-lying nuclear states in Ga73 has recently been experimentally determined: a 1/2− spin-parity for the ground state was measured in a laser spectroscopy experiment, while a Jπ=3/2− level was observed in transfer reactions. This scenario is supported by Coulomb excitation studies, which set a limit for the energy splitting of 0.8 keV. In this work, we report on the study of the excited structure of Ga73 populated in the β decay of Zn73 produced at ISOLDE, CERN. Using β-gated, γ-ray singles, and γ-γ coincidences, we have searched for energy differences to try to delimit the ground-state energy splitting, providing a more stringent energy difference limit. Three new half-lives of excited states in Ga73 have been measured using the fast-timing method with LaBr3(Ce) detectors. From our study, we help clarify the excited structure of Ga73 and we extend the existing Zn73 decay to Ga73 with 8 new energy levels and 35 γ transitions. We observe a 195-keV transition consistent with a γ ray de-exciting a short-lived state in the β-decay parent Zn73.