Search for the Ga-73 ground-state doublet splitting in the beta decay of Zn-73

The existence of two close-lying nuclear states in Ga-73 has recently been experimentally determined: a 1/2(-) spin-parity for the ground state was measured in a laser spectroscopy experiment, while a J(pi\) = 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 Ga-73 populated in the beta decay of Zn-73 produced at ISOLDE, CERN. Using beta-gated, gamma-ray singles, and gamma-gamma 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 Ga-73 have been measured using the fast-timing ;method with LaBr3(Ce) detectors. From our study, we help clarify the excited structure of Ga-73 and we extend the existing Zn-73 decay to Ga-73 with 8 new energy levels and 35 gamma transitions. We observe a 195-keV transition consistent with a gamma ray de-exciting a short-lived state in the beta-decay parent Zn-73.