Zdependence of theN=152deformed shell gap: In-beam γ-ray spectroscopy of neutron-richPu245,246

We have measured in-beam {gamma} rays in the neutron-rich {sup 246}Pu{sub 152} and {sup 245}Pu{sub 151} nuclei by means of {sup 244}Pu({sup 18}O, {sup 16}O){sup 246}Pu and {sup 244}Pu({sup 18}O, {sup 17}O){sup 245}Pu neutron transfer reactions, respectively. The {gamma} rays emitted from {sup 246}Pu ({sup 245}Pu) were identified by selecting the kinetic energy of scattered {sup 16}O ({sup 17}O) detected by Si {delta}E-E detectors. The ground-state band of {sup 246}Pu was established up to the 12{sup +} state. We have found that the shell gap of N=152 is reduced in energy with decreasing atomic number by extending the systematics of the one-quasiparticle energies in N=151 nuclei into those in {sup 245}Pu. This reduction of the shell gap clearly affects the 2{sup +} energy of the ground-state band of {sup 246}Pu.