6828Ni40:: Magicity versus superfluidity -: art. no. 092501

The neutron-rich Ni-66,Ni-68 have been produced at GANIL via interactions of a 65.9A MeV Zn-70 beam with a Ni-58 target. Their reduced transition probability B(E2; 0(1)(+) --> 2(+)) has been measured for the first time by Coulomb excitation in a Pb-208 target at intermediate energy. The B(E2) value for Ni-68(40) is unexpectedly small. An analysis in terms of large scale shell model calculations stresses the importance of proton core excitations to reproduce the B(E2) values and indicates the erosion of the N = 40 harmonic-oscillator subshell by neutron-pair scattering.