Soichiro Shigematsu

Ground-state band of the neutron-rich transuranium nucleus 250Cm154

The ground-state band of the neutron-rich transuranium nucleus 250 Cm was established up to spin 12 by in-beam γ-ray spectroscopy using the two-neutron transfer reaction with a 248 Cm target and a 162 MeV 18 O beam. Deexcitation γ rays in 250 Cm were identified by selecting the kinetic energies of 16 O particles using Si Δ E – E detectors. The moment of inertia of 250 Cm 154 is considerably smaller than that of 248 Cm 152 , which supports the existence of the deformed subshell closure at N =152 in Cm isotopes.

In-beam γ-ray study of the neutron-rich nuclei 240U, 246Pu, and 250Cm produced by the (18O, 16O) reaction

We have measured deexcitation γ rays in the neutron-rich nuclei of 240U, 246Pu, and 250Cm produced by the (18O, 16O) two-neutron transfer reactions, in coincidence with the 16O particles using Si ΔE−E detectors. The γ rays in these nuclei were identified by selecting the kinetic energies of 16O particles, which correspond to the excitation energies in the residual nuclei below the neutron separation energies. The ground-state bands of 240U, 246Pu, and 250Cm were established up to 12+ states and the Kπ = 0− octupole band of 240U was established up to 9− states. The systematics of the moments of inertia of the ground-state bands for actinide nuclei shows that the deformed subshell closure at N = 152 is sustained for 96Cm isotopes and that it disappears for 94Pu isotopes.

Z dependence of the N=152 deformed shell gap: In-beam {gamma}-ray spectroscopy of neutron-rich {sup 245,246}Pu

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.