Isomeric and ground-state properties of Pt-171(78), Os-167(76), and W-163(74)

Decay paths, half-lives, and excitation energies of the i13/2 bandheads of the neutron-deficient nuclei Pt171, Os167, and W163 have been established for the first time. Gamma-ray transitions, X-rays, and internal conversion electrons have been observed, allowing internal-conversion coefficients to be measured and B(M2) reduced transition probabilities to be extracted. These results elucidate the low-lying single-quasiparticle structures and give the energy level spacings between the νf7/2, νh9/2, and νi13/2 quasineutron states for all three nuclei. Moreover, ground-state spin assignments have been made for the first time, along with the measurement of the α-decay branching ratio for Pt171. The decay paths of the i13/2 bandheads were followed by favored α decays, indicating that all three nuclei have the same Iπ=7/2− ground state

Lifetimes of odd-spin yrast states in Hg-182

Lifetimes of excited states in 182Hg were extracted from recoil-gated γ-ray spectra and recoil-gated γγ-coincidence matrices using the recoil distance Doppler-shift method. States were populated using the 96Mo(88Sr,2n)182Hg fusion-evaporation reaction. Measured lifetimes allowed transition probabilities, transition quadrupole moments, quadrupole deformation parameters, and transition dipole moments to be deduced for the band formed by the odd-spin yrast states. The experimental results confirm the low degree of octupole collectivity in this mass region.status: publishe

Discovery of W-157 and Os-161

The nuclides 157W and 161Os have been discovered in reactions of 58Ni ion beams with a 106Cd target. The 161Os α-decay energy and half-life were 6890±12 keV and 640±60 μs. The daughter 157W nuclei β-decayed with a half-life of 275±40 ms, populating both low-lying α-decaying states in 157Ta, which is consistent with a 7/2− ground state in 157W. Fine structure observed in the α decay of 161Os places the lowest excited state in 157W with Iπ =9/2− at 318±30 keV. The branching ratio of 5.5+3.1 −2.2% indicates that 161Os also has a 7/2− ground state. Shell-model calculations analysing the effects of monopole shifts and a tensor force on the relative energies of 2f7/2 and 1h9/2 neutron states in N=83 isotones are presented