Coulomb excitation of the 3 isomer in 70Cu
Phys. Rev. C
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 𝐼𝜋 = 3− state in 70Cu (𝑍=29, 𝑁=41). While first results using a 𝐼𝜋=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.