Coulomb excitation of the 3− isomer in 70Cu

Post-accelerated isomerically purified radioactive beams, available at the CERN On-Line Isotope Mass Separator facility using the resonant ionization laser technique, have been used to study the Coulomb excitation of the I π = 3− state in 70Cu (Z = 29, N = 41). While first results using a I π = 6− beam were reported previously, the present complementary experiment allows us to complete the study of the multiplet of states (3−, 4−, 5−, 6−) arising from the π2p3/2ν1g9/2 configuration. Besides the known γ -ray transition deexciting the 4− state, a ground-state γ ray of 511(3) keV was observed for the first time and was unambiguously associated with the 5− state deexcitation. This observation fixes the energy, spin, and parity of this state, completing the low-energy level scheme of 70Cu. B(E2) values for all possible E2 transitions within the multiplet were determined. A comparison with large-scale shell model calculations using different interactions and valence spaces shows the importance of proton excitation across the Z = 28 shell gap and the role of the 2d5/2 neutron orbital.status: publishe