Shapes, softness, and nonyrast collectivity in 186W

Nonyrast, excited states in neutron-rich 186W were populated via inelastic-scattering reactions using beams of 136Xe nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particleγ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The Kπ = 2+ (γ), Kπ = 0+ and Kπ = 2− (octupole) rotational side bands were extended to spins 14¯h,12¯ h, and 13¯h, respectively. A staggering pattern observed in the energies of levels in the Kπ = 2+ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. The odd-even staggering of states in the Kπ = 2− band was found to exhibit a phase opposite to that seen in the γ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in 186W

N=151Pu, Cm and Cf nuclei under rotational stress: Role of higher-order deformations

Fast-rotating N=151 isotones 245Pu, 247Cm and 249Cf have been studied through inelastic excitation and transfer reactions with radioactive targets. While all have a ground-state band built on a νj15/2[734]9/2- Nilsson configuration, new excited bands have also been observed in each isotone. These odd-N excited bands allow a comparison of the alignment behavior for two different configurations, where the νj15/2 alignment is either blocked or allowed. The effect of higher order deformations is explored through cranking calculations, which help clarify the elusive nature of νj15/2 alignments

Shapes, softness, and nonyrast collectivity in 186W^{186}\mathrm{W}

International audienceNonyrast, excited states in neutron-rich W186 were populated via inelastic-scattering reactions using beams of Xe136 nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particle-γ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The Kπ=2+ (γ), Kπ=0+ and Kπ=2− (octupole) rotational side bands were extended to spins 14ℏ, 12ℏ, and 13ℏ, respectively. A staggering pattern observed in the energies of levels in the Kπ=2+ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. The odd-even staggering of states in the Kπ=2− band was found to exhibit a phase opposite to that seen in the γ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in W186

N=151Pu,Cm and Cf nuclei under rotational stress: Role of higher-order deformations

Fast-rotating N=151 isotones 245Pu, 247Cm and 249Cf have been studied through inelastic excitation and transfer reactions with radioactive targets. While all have a ground-state band built on a νj15/2[734]9/2− Nilsson configuration, new excited bands have also been observed in each isotone. These odd-N excited bands allow a comparison of the alignment behavior for two different configurations, where the νj15/2 alignment is either blocked or allowed. The effect of higher order deformations is explored through cranking calculations, which help clarify the elusive nature of νj15/2 alignments. Keywords: Superheavy, Neutron-rich, Inelastic and transfer reactions, Rotational alignments, Higher-order deformation

γ -soft Ba 146 and the role of nonaxial shapes at N≈90

Low-spin states in the neutron-rich, N=90 nuclide Ba146 were populated following β decay of Cs146, with the goal of clarifying the development of deformation in barium isotopes through delineation of their nonyrast structures. Fission fragments of Cs146 were extracted from a 1.7-Ci Cf252 source and mass selected using the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility. Low-energy ions were deposited at the center of a box of thin β detectors, surrounded by a highly efficient high-purity Ge array. The new Ba146 decay scheme now contains 31 excited levels extending up to ∼2.5 MeV excitation energy, double what was previously known. These data are compared to predictions from the interacting boson approximation (IBA) model. It appears that the abrupt shape change found at N=90 in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the γ degree of freedom