Discovery of W-157 and Os-161

• Published in: Physics letters. B 2010-06, Vol.690 (1), p.15-18
• Main Authors: Bianco, L., Page, R.D., Darby, I.G., Joss, D.T., Simpson, J., Al-Khalili, J.J., Cannon, A.J., Cederwall, B., Eeckhaudt, S., Ertürk, S., Gall, B., Hornillos, M.B.G., Grahn, T., Greenlees, P.T., Hadinia, B., Heyde, K., Jakobsson, U., Jones, P.M., Julin, R., Juutinen, S., Ketelhut, S., Labiche, M., Leino, M., Leppänen, A.-P., Nyman, M., O'Donnell, D., Paul, E.S., Petri, M., Peura, P., Puurunen, A., Rahkila, P., Ruotsalainen, P., Sandzelius, M., Sapple, P.J., Sarén, J., Scholey, C., Smirnova, N., Steer, A.N., Stevenson, P.D., Suckling, E.B., Thomson, J. M., Uusitalo, J., Venhart, M.
• Format: Article
• Language: English
• Subjects: 310 MeV beam energy; Deduced neutron single-particle configurations in Os-161; Fysik; gas-filled recoil separator; Measured E alpha; NATURAL SCIENCES; NATURVETENSKAP; NUCLEAR REACTIONS Ni-58+Cd-106 at 290; Nuclear Theory; Physics; Shell model calculations; Si detectors; t(1/2); W-157
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2010.04.056

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 View the MathML source 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.