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1. Decays of New Nuclides and Isomers Beyond the Proton Drip Line—The Influence of Neutron Configurations.

Author

Page, R. D., Bianco, L., Darby, I. G., Joss, D. T., Simpson, J., Al-Khalili, J. S., Cannon, A. J., Cooper, R. J., Eeckhaudt, S., Ertürk, S., Gall, B., Grahn, T., Greenlees, P. T., Hadinia, B., Jones, P. M., Judson, D. S., Julin, R., Juutinen, S., Ketelhut, S., and Labiche, M.

Subjects
*EXOTIC nuclei, *NEUTRONS, *PROTONS, *IONS, *SPECTROMETERS
Abstract

The energy of the vh9/2 orbital in nuclei above N = 82 drops rapidly in energy relative to the vf7/2 orbital as the occupancy of the πh11/2 orbital increases. These two neutron orbitals become nearly degenerate as the proton drip line is approached. In this work, we have discovered the new nuclides 161Os and 157W, and studied the decays of the proton emitter 160Re in detail. The 161Os and 160Re nuclei were produced in reactions of 290, 300 and 310 MeV 58Ni ions with an isotopically enriched 106Cd target, separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The 161Os α a decays populated the new nuclide 157W, which decayed by β-particle emission. The β decay fed the known α-decaying 1/2+ and 11/2- states in 157Ta, which is consistent with a vf7/2 ground state in 157W. The measured α-decay energy and half-life for 161Os correspond to a reduced α-decay width that is compatible with s-wave α-particle emission, implying that its ground state is also a vf7/2 state. Over 7000 160Re nuclei were produced and the γ decays of a new isomeric state feeding the πd3/2 level in 160Re were discovered, but no evidence for the proton or a decay of the expected πh11/2 state could be found. The isomer decays offer a natural explanation for this non-observation and provides a striking example of the influence of the near degeneracy of the vh9/2 and vf7/2 orbitals on the properties of nuclei in this region. [ABSTRACT FROM AUTHOR]

Published
2008
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2. Discovery of W-157 and Os-161

Author

Bianco, L, Page, RD, Darby, IG, Joss, DT, Simpson, J, Al-Khalili, JJ, Cannon, AJ, Cederwall, B, Eeckhaudt, S, Erturk, S, Gall, B, Hornillos, MBG, Grahn, T, Greenlees, PT, Hadinia, B, Heyde, Kristiaan, Jakobsson, U, Jones, PM, Julin, R, Juutinen, S, Ketelhut, S, Labiche, M, Leino, M, Leppanen, AP, Nyman, M, O'Donnell, D, Paul, ES, Petri, M, Peura, P, Puurunen, A, Rahkila, P, Ruotsalainen, P, Sandzelius, M, Sapple, PJ, Saren, J, Scholey, C, Smirnova, NA, Steer, AN, Stevenson, PD, Suckling, EB, Thomson, J, Uusitalo, J, Venhart, M, Scholey, Catherine -- 0000-0002-8743-6071, Stevenson, Paul -- 0000-0003-2645-2569, O'Donnell, David -- 0000-0002-4710-3803, Petri, Marina -- 0000-0002-3740-6106, Cederwall, Bo -- 0000-0003-1771-2656, Darby, Iain -- 0000-0003-2091-2616, Jones, Pete -- 0000-0001-7480-6603, Jakobsson, Ulrika -- 0000-0001-9741-141X, Gomez Hornillos -- 0000-0002-9282-9195, Grahn, Tuomas -- 0000-0002-6255-2279, Peura, Pauli -- 0000-0002-8541-0169, and [Bianco, L. -- Page, R. D. -- Darby, I. G. -- Joss, D. T. -- Grahn, T. -- Paul, E. S. -- Petri, M. -- Sapple, P. J. -- Thomson, J.] Univ Liverpool, Dept Phys, Liverpool L69 7ZE, Merseyside, England -- [Simpson, J. -- Hornillos, M. B. Gomez -- Labiche, M. -- O'Donnell, D.] STFC, Daresbury Lab, Warrington WA4 4AD, Cheshire, England -- [Al-Khalili, J. J. -- Cannon, A. J. -- Stevenson, P. D. -- Suckling, E. B.] Univ Surrey, Dept Phys, Guildford GU2 7XH, Surrey, England -- [Cederwall, B. -- Hadinia, B. -- Sandzelius, M.] Royal Inst Technol, Alba Nova Ctr, S-10691 Stockholm, Sweden -- [Eeckhaudt, S. -- Greenlees, P. T. -- Jakobsson, U. -- Jones, P. M. -- Julin, R. -- Juutinen, S. -- Ketelhut, S. -- Leino, M. -- Leppanen, A. -P. -- Nyman, M. -- Peura, P. -- Puurunen, A. -- Rahkila, P. -- Ruotsalainen, P. -- Saren, J. -- Scholey, C. -- Steer, A. N. -- Uusitalo, J. -- Venhart, M.] Univ Jyvaskyla, Dept Phys, FIN-40014 Jyvaskyla, Finland -- [Erturk, S.] Nigde Univ, Fen Edebiyat Fak, Fizik Bolumu, Nigde, Turkey -- [Gall, B.] ULP Strasbourg, IPHC, CNRS, IN2P3, F-67037 Strasbourg 2, France -- [Heyde, K.] Univ Ghent, Vakgrp Subatomaire Stralingsfysika, B-9000 Ghent, Belgium -- [Smirnova, N. A.] CEN Bordeaux Gradignan, F-33175 Gradignan, France

Subjects
Deduced neutron single-particle configurations in Os-161, W-157, Si detectors, NUCLEI, t(1/2), TOTAL DATA READOUT, Measured E alpha, t(1/2), Shell model calculations, NUCLEAR REACTIONS Ni-58+Cd-106 at 290, Physics and Astronomy, Measured E alpha, Deduced neutron single-particle configurations in Os-161, W-157, NEUTRON-DEFICIENT ISOTOPES, gas-filled recoil separator, PROTON DRIP-LINE, 310 MeV beam energy, NUCLEAR REACTIONS Ni-58+Cd-106 at 290, 300, 310 MeV beam energy, gas-filled recoil separator, Si detectors
Abstract

WOS: 000278933900003, The nuclides W-157 and Os-161 have been discovered ill reactions of Ni-58 ion beams with a Cd-106 target. The Os-161 alpha-decay energy and half-life were 6890 +/- 12 keV and 640 +/- 60 mu s. The daughter W-157 nuclei beta-decayed with a half-life of 275 +/- 40 ms, populating both low-lying alpha-decaying states in Ta-157, which is consistent with a 7/2(-) ground state in W-157. Fine structure observed in the alpha decay of Os-161 places the lowest excited state in W-157 with 1(pi) = 9/2(-) at 318 +/- 30 key. The branching ratio of 5.5(-2.2)(+3.1)% indicates that Os-161 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 2f(7/2) and 1h(9/2) neutron states in N = 83 isotones are presented. (C) 2010 Elsevier B.V. All rights reserved., Jyvaskyla; United Kingdom Science and Technology Facilities Council; Swedish Natural Science Research Council; Academy of Finland [44875, 209430, 111965]; European Union [R113-CT-2004-506065, HPMT-CT-2001-00250]; Science and Technology Facilities Council [EP/C015266/1, EP/C015371/1, ST/G008671/1, ST/F012012/1, ST/J000108/1, EP/C543157/1, ST/G008620/1, ST/F012039/1], We thank the accelerator staff at Jyvaskyla for their excellent support and Paul Morrall from Daresbury Laboratory for making the targets. This work was supported by the United Kingdom Science and Technology Facilities Council; the Swedish Natural Science Research Council; the Academy of Finland through the Finnish Centre of Excellence Programme (project 44875 Nuclear and Condensed Matter Physics Programme at JYFL) and support for C.S. (contract 209430) and P.T.G. (contract 111965); the European Union Sixth Framework contract EURONS (R113-CT-2004-506065) and the European Union Marie Curie Programme (contract HPMT-CT-2001-00250).

Published
2010

3. Discovery of W-157 and Os-161

Author

Bianco, L., Page, R. D., Darby, I. G., Joss, D. T., Simpson, J., Al-Khalili, J. J., Cannon, A. J., Cederwall, Bo, Eeckhaudt, S., Erturk, S., Gall, B., Hornillos, M. B. Gomez, Grahn, T., Greenlees, P. T., Hadinia, Baharak, Heyde, K., Jakobsson, U., Jones, P. M., Julin, R., Juutinen, S., Ketelhut, S., Labiche, M., Leino, M., Leppanen, A. -P, Nyman, M., O'Donnell, D., Paul, E. S., Petri, M., Peura, P., Puurunen, A., Rahkila, P., Ruotsalainen, P., Sandzelius, Mikael, Sapple, P. J., Saren, J., Scholey, C., Smirnova, N. A., Steer, A. N., Stevenson, P. D., Suckling, E. B., Thomson, J., Uusitalo, J., Venhart, M., Bianco, L., Page, R. D., Darby, I. G., Joss, D. T., Simpson, J., Al-Khalili, J. J., Cannon, A. J., Cederwall, Bo, Eeckhaudt, S., Erturk, S., Gall, B., Hornillos, M. B. Gomez, Grahn, T., Greenlees, P. T., Hadinia, Baharak, Heyde, K., Jakobsson, U., Jones, P. M., Julin, R., Juutinen, S., Ketelhut, S., Labiche, M., Leino, M., Leppanen, A. -P, Nyman, M., O'Donnell, D., Paul, E. S., Petri, M., Peura, P., Puurunen, A., Rahkila, P., Ruotsalainen, P., Sandzelius, Mikael, Sapple, P. J., Saren, J., Scholey, C., Smirnova, N. A., Steer, A. N., Stevenson, P. D., Suckling, E. B., Thomson, J., Uusitalo, J., and Venhart, M.

Abstract

The nuclides W-157 and Os-161 have been discovered ill reactions of Ni-58 ion beams with a Cd-106 target. The Os-161 alpha-decay energy and half-life were 6890 +/- 12 keV and 640 +/- 60 mu s. The daughter W-157 nuclei beta-decayed with a half-life of 275 +/- 40 ms, populating both low-lying alpha-decaying states in Ta-157, which is consistent with a 7/2(-) ground state in W-157. Fine structure observed in the alpha decay of Os-161 places the lowest excited state in W-157 with 1(pi) = 9/2(-) at 318 +/- 30 key. The branching ratio of 5.5(-2.2)(+3.1)% indicates that Os-161 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 2f(7/2) and 1h(9/2) neutron states in N = 83 isotones are presented. (C) 2010 Elsevier B.V. All rights reserved., QC 20101213

Published
2010
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