Evolution of single-particle strength in neutron-rich 71 Cu

The strength functions of the π f 5 / 2 , π p 3 / 2 and π f 7 / 2 orbitals in neutron-rich 71 Cu were obtained in a 72 Zn(d, 3 He) 71 Cu proton pick-up reaction in inverse kinematics using a radioactive beam of 72 Zn at 38 MeV/u. A dedicated set-up was developed to overcome the experimental challenges posed by the low cross section of the reaction and the low energy of the outgoing 3 He particles. The excitation-energy spectrum was reconstructed and spectroscopic factors were obtained after analysis of the angular distributions with the finite-range Distorted-Wave Born Approximation (DWBA). The results show that unlike for the π f 5 / 2 orbital and contrary to earlier interpretation, the π f 7 / 2 single-particle strength distribution is not appreciably affected by the addition of neutrons beyond N = 40 .