Systematic Study of β-Decay Half-Lives in the Vicinity of 78Ni

Experimental study of β-decay properties for nuclei around Ni is of great importance as Ni is probably the most neutron-rich nuclide known so far. Observables like β-decay half-life (T1/2), β-decay Q value (Qβ), neutron emission probability (Pn) can serve as benchmarks for one to understand the nuclear structure far from the valley of stability. Results from the experiment allow for systematic study and comparison between different global mass models or various theories including shell model calculations, which will largely extend the present knowledge of nuclear structure towards neutron drip-line. In order to produce the secondary beam containing very neutron-rich nuclei around Ni, the experiment was performed as part of EURICA campaign at Radioactive Isotope beam factory (RIBF) operated by RIKEN Nishina Center (RNC) and Center of Nuclear Study (CNS), University of Tokyo. A high intensity U beam was extracted from accelerator complex at RIBF with an energy of 345 MeV/nucleon. The secondary beam was generated by the in-flight fission of U in a 3 mm Be target. The fragments from fission of U were analyzed in the BigRIPS and ZeroDegree with an event-by-event mode. A highly segmented active stopper, WAS3ABi, was mounted after the last focal plane of ZeroDegree spectrometer, F11, for the implantation of fragments of interest transimitted through BigRIPS and ZeroDegree. The ion-β-γ correlation was obtained to study the half-lives as well as β-delayed γ-ray spectroscopy of exotic nuclei around Ni. In this presentation, new half-lives of Co, Co, Ni, Cu, Cu, Zn, Ga, and Ge, which was measured for the first time experimentally, will be reported. Half-life of nuclide such as Ni, which had been measured in previous experiment but resulted in a large uncertainty, was re-measured in this work with a much higher precision. The shell gap effect on half-lives and magicity at Z = 28 and N = 50 will be discussed based on the data from this experiment together with previous ones from literature. APPC12 The 12th Asia Pacific Physics Conference