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).
Perru
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O
Institut de Physique Nucléaire, IN2P3-CNRS, F-91406 Orsay Cedex, France.
Sorlin
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Franchoo
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Azaiez
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Bouchez
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Bourgeois
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Chatillon
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Daugas
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Dlouhy
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Dombrádi
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Donzaud
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Gaudefroy
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Grawe
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Grévy
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Guillemaud-Mueller
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Hammache
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Ibrahim
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Le Coz
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Lukyanov
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Matea
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Mrazek
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Nowacki
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Penionzhkevich
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de Oliveira Santos
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Pougheon
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Saint-Laurent
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Sletten
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Stanoiu
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Stodel
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Theisen
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Verney
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