Proton single particle energies next to 78Ni: Spectroscopy of 77Cu via single proton knock-out reaction

Abstract Excited states of 77 Cu have been investigated by use of single proton knock-out reaction at the Radioactive Isotope Beam Factory in RIKEN in order to reveal the main components of the proton single-particle states. Three excited states were observed at 271, 902 and 2068 keV in 77 Cu. The lowest-energy excited state follows the trend predicted for the crossing of the 3 / 2 1 − and 5 / 2 1 − states. Comparing the excitation energies of the 3 / 2 − , 5 / 2 − and 7 / 2 − levels from 69 Cu to 77 Cu one can see that the Z = 28 shell gap between the p 3 / 2 and f 7 / 2 states is rather stable, while the f 5 / 2 − f 7 / 2 spin–orbit splitting decreases by ∼1.5 MeV in agreement with shell model calculations using the tensor force.