Enhanced core polarization in (70)Ni and (74)Zn

• Published in: Physical review letters Vol. 96; no. 23; p. 232501
• Main Authors: Perru, O, Sorlin, O, Franchoo, S, Azaiez, F, Bouchez, E, Bourgeois, C, Chatillon, A, Daugas, J M, Dlouhy, Z, Dombrádi, Zs, Donzaud, C, Gaudefroy, L, Grawe, H, Grévy, S, Guillemaud-Mueller, D, Hammache, F, Ibrahim, F, Le Coz, Y, Lukyanov, S M, Matea, I, Mrazek, J, Nowacki, F, Penionzhkevich, Yu-E, de Oliveira Santos, F, Pougheon, F, Saint-Laurent, M G, Sletten, G, Stanoiu, M, Stodel, C, Theisen, Ch, Verney, D
• Format: Journal Article
• Language: English
• Published: United States 16.06.2006
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.96.232501

The reduced transition probabilities B(E2;0(+) --> 2(+)(1)) of the neutron-rich (74)Zn and (70)Ni nuclei have been measured by Coulomb excitation in a (208)Pb target at intermediate energy. These nuclei have been produced at Grand Accélérateur National d'Ions Lourds via interactions of a 60A MeV (76)Ge beam with a Be target. The B(E2) value for (70)Ni(42) 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 (74)Zn(44). The enhanced proton core polarization in (70)Ni is attributed to the monopole interaction between the neutron in the g(9/2) and protons in the f(7/2) and f(5/2) spin-orbit partner orbitals. This interaction could result in a weakening of magicity in (78)Ni(50).