Background: Detailed spectroscopy of neutron-rich odd-A Cu isotopes is of great importance for studying the shell evolution in the region of Ni78. While there is experimental information on excited states in Cu69-73,77,79 isotopes, the information concerning Cu75 is very limited. Purpose: Experimentally observed single-particle, core-coupling, and proton-hole intruder states in Cu75, will complete the systematics of these states in the chain of isotopes. Method: Excited states in Cu75 were populated in the β decay of Ni75 isotopes. The Ni nuclei were produced by the in-flight fission of U238 projectiles, and were separated, identified, and implanted in a highly segmented Si detector array for the detection of the β-decay electrons. The β-delayed γ rays were detected in a HPGe cluster array. Monte Carlo shell model calculations were performed using the A3DA interaction built on the pfg9/2d5/2 model space for both neutrons and protons. Results: A level scheme of Cu75 was built up to ≈4 MeV by performing a γ-γ coincidence analysis. The excited states below 2 MeV were interpreted based on the systematics of neutron-rich odd-A Cu isotopes and the results of the shell model calculations. Conclusions: The evolution of the single-particle, core-coupling, and proton-hole intruder states in the chain of neutron-rich odd-A Cu isotopes is discussed in the present work, in connection with the newly observed level structure of Cu75.
Bibliographical noteFunding Information:
This work was carried out at the RIBF operated by RIKEN Nishina Center, RIKEN and CNS, University of Tokyo. The research leading to the results has received funding from the Research Council of Norway under project Grants No. 240104 and No. 213442 and from KAKENHI (under Grants No. 25247045, No. 23.01752, and No. 25800130); U.S. DOE Grant No. DE-FG02-91ER-40609; German BMBF Grant No. 05P19RDFN1 and DFG Grant No. SFB 1245; Spanish Ministerio de Ciencia e Innovación Contracts No. FPA2009-13377C02 and No. FPA2011-29854-C04; and GINOP-2.3.3-15-2016-00034 and the Hungarian Scientific Research Fund OTKA Contract No. K128947. The Monte Carlo shell-model calculations were performed on K computer at RIKEN AICS (hp140210, hp150224, hp160211). This work was supported in part by the HPCI Strategic Program (The Origin of Matter and the Universe), by “Priority Issue on Post-K computer” (Elucidation of the Fundamental Laws and Evolution of the Universe) (hp160211), and by CNS-RIKEN joint project for large-scale nuclear structure calculations. The authors acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. Part of the WAS3ABi was supported by the Rare Isotope Science Project which is funded by the Ministry of Education, Science and Technology (MEST) and National Research Foundation (NRF) of Korea.