The reduced transition probabilities B(E2;0+→21+) of the neutron-rich Zn74 and Ni70 nuclei have been measured by Coulomb excitation in a Pb208 target at intermediate energy. These nuclei have been produced at Grand Accélérateur National d'Ions Lourds via interactions of a 60AMeV Ge76 beam with a Be target. The B(E2) value for Ni4270 is unexpectedly large, which indicates that neutrons added above N=40 strongly polarize the Z=28 proton core. In the Zn isotopic chain, the steep rise of B(E2) values beyond N=40 continues up to Zn4474. The enhanced proton core polarization in Ni70 is attributed to the monopole interaction between the neutron in the g9/2 and protons in the f7/2 and f5/2 spin-orbit partner orbitals. This interaction could result in a weakening of magicity in Ni5078.
ASJC Scopus subject areas
- Physics and Astronomy(all)