Low-lying excitations in Ni 72

Abstract

A. I. Morales et al.; 14 págs.; 9 figs.; 3 tabs. ; Low-lying excited states in Ni72 have been investigated in an in-flight fission experiment at the RIBF facility of the RIKEN Nishina Center. The combination of the state-of-the-art BigRIPS and EURICA setups has allowed for a very accurate study of the β decay from Co72 to Ni72, and has provided first experimental information on the decay sequence Fe72→Co72→Ni72 and on the delayed neutron-emission branch Co73→Ni72. Accordingly, we report nearly 60 previously unobserved γ transitions which deexcite 21 new levels in Ni72. Evidence for the location of the so-sought-after (42+),(62+), and (81+) seniority states is provided. As well, the existence of a low-spin β-decaying isomer in odd-odd neutron-rich Co isotopes is confirmed for mass A=72. The new experimental information is compared to simple shell-model calculations including only neutron excitations across the fpg shells. It is shown that, in general, the calculations reproduce well the observed states. ©2016 American Physical Society ; The excellent work of the RIKEN accelerator staff for providing a stable and high-intensity 238U beam is acknowledged. Part of he WAS3ABi was supported by the Rare Isotope Science Project, which is funded by the Ministry of Science, ICT and Future Planning (MSIP) and National Research Foundation (NRF) of Korea. This work is cofinanced by the European Union and the European Social Fund. Support from italian Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale (PRIN) Grant No. 2001024324_01302, the NuPNET-ERANET within the NuPNET GANAS project under Grant Agreement No. 202914, and the European Union within the 7th Framework Program FP7/2007-2013 under Grant Agreement No. 262010 ENSAR-INDESYS is acknowledged. This work was also financed by the Spanish Ministerio de Ciencia e Innovación under ContractsNo. FPA2009-13377-C02 and No. FPA2011-29854-C04, the Hungarian Research Fund OTKA Contract No. K100835 and No. K106035, the European Commission through the Marie Curie Actions Contract No. PIEFGA-2001-30096, and by the Japanese JSPS KAKENHI Grants No. 24740188 and No. 25247045 ; Peer Reviewed