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


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).

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@article{Perru2006EnhancedCP, title={Enhanced core polarization in (70)Ni and (74)Zn.}, author={Olivier Perru and O . Sorlin and Serge Franchoo and Fairouz Azaiez and E. Bouchez and Christian Bourgeois and A . Chatillon and J-M Daugas and Z . Dlouhy and Zs . Dombr{\'a}di and Corinne Donzaud and L . Gaudefroy and Hubert Grawe and S . Gr{\'e}vy and D. Guillemaud-Mueller and F . Hammache and Fatima Ibrahim and Y. L. Le Coz and Sergey Lukyanov and I . Matea and Jir{\'i} Mr{\'a}zek and Fr{\'e}d{\'e}ric Nowacki and Yu-E Penionzhkevich and Felipe de Oliveira Santos and F. Pougheon and M-G Saint-Laurent and Geir Sletten and M . Stanoiu and Ch Stodel and Ch . Theisen and David Verney}, journal={Physical review letters}, year={2006}, volume={96 23}, pages={232501} }