Orateur
Description
78Ni is a unique doubly magic nucleus far from beta stability line, the only one decaying with β-delayed neutron emission channel. Its decay properties influence the early r-process nucleosynthesis and the beta decays of exotic nuclei north-east of Z=28 and N=50. Nuclei in the 78Ni region were created with the 345 MeV/u 238U beam reaching nearly 70 part*nanoAmp. Fragmentation products were separated by means of BigRIPS spectrometer at RIKEN (Wako, Japan). The spectroscopy of radiation emitted by beta-delayed neutron precursors was performed using BRIKEN 3He array [1] modified to achieve larger gamma efficiency [2]. ORNL contributions included 87% of 3He neutron detection volume and two Ge clovers. The fragment implantation and decay array were consisting of four smaller double-sided Si-strip counters of WASABI complemented by a position sensitive YSO scintillator developed at the UTK. The BigRIPS setting was maximized for the transmission of 82Cu. Isotopes between 61V-69V up to 95Br-97Br were produced and identified. The total rate of identified 78Ni ions was around 65,000, with about 40,000 ions implanted for decay study. Beta-gamma and beta-neutron-gamma decay channels were identified for 78Ni precursor. The P1n branching ratio of about 27(4)% was determined from the analysis [3] of β-1n decay pattern. New levels in 78Cu as well as new level associated with proton p3/2 state in Z=29 77Cu were observed. The accepted proposal to study 78Ni decay with the recently commissioned ORNL’s Modular Total Absorption Spectrometer at the Facility for Rare Isotopes Beams will be briefly presented.
[1] A. Tarifeño-Saldivia et al., Jour. of Instrum. 12, P04006 (2017).
[2] R. Yokoyama et al., Phys. Rev. C 100, 031302(R) (2019).
[3] B. C. Rasco et al., Nucl. Instrum. Methods. Phys. Res. A 911, 79 (2018).
Supported by the U.S. DOE Office of Nuclear Physics under contracts DE-AC05-00R22725 (ORNL) and DE-FG02-96ER40983 (UTK)
