68 28 Ni 40 : Magicity versus Superfluidity

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