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Öğe Decay of the high-spin isomer in Re-160: Changing single-particle structure beyond the proton drip line(ELSEVIER SCIENCE BV, 2011) Darby, I. G.; Page, R. D.; Joss, D. T.; Simpson, J.; Bianco, L.; Cooper, R. J.; Judson, D. S.A new high-spin isomeric state (t(1/2) = 2.8 +/- 0.1 mu s) in Re-160 has been identified. This high-spin isomer is unique in that it only decays by gamma-decay and not by proton or alpha-particle emission as is the case in every other proton emitter between Z = 64 and 80. Shell model calculations indicate how the convergence of the h(9/2) and f(7/2) neutron levels in this region could open up a gamma-decay path from the high-spin isomer to the low-spin ground state of 160Re. providing a natural explanation for this anomalous absence of charged-particle emission. The consequences of these observations for future searches for proton emission from even more exotic nuclei and in-beam spectroscopic studies are considered. (C) 2010 Elsevier B.V. All rights reserved.Öğe Discovery of W-157 and Os-161(ELSEVIER SCIENCE BV, 2010) Bianco, L.; Page, R. D.; Darby, I. G.; Joss, D. T.; Simpson, J.; Al-Khalili, J. J.; Greenlees, P. T.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.Öğe gamma-ray spectroscopy of Ta-163(AMER PHYSICAL SOC, 2009) Sandzelius, M.; Cederwall, B.; Ganioglu, E.; Thomson, J.; Andgren, K.; Bianco, L.; Johnson, A.Excited states in Ta-163 have been identified for the first time using the Cd-106(Ni-60,3p) fusion evaporation reaction. gamma rays were detected using the JUROGAM gamma-ray spectrometer and recoil discrimination was achieved using the recoil ion transport unit (RITU) gas-filled separator in conjunction with the GREAT spectrometer situated at the focal plane of the RITU. The yrast states are assigned to a strongly coupled rotational band based on a pi h(11/2) configuration. This structure exhibits large signature splitting at low spins that disappears after the paired band crossing because of the alignment of a pair of i(13/2) neutrons. This effect is ascribed to triaxial shape changes induced by the core-polarizing properties of the deformation-aligned h(11/2) proton and the rotation-aligned i(13/2) neutrons. Two additional strongly coupled band structures have been established and are discussed in terms of octupole-vibrational and two-quasiparticle excitations built on the yrast structure. The experimental results are compared with predictions from cranked-shell-model and total-Routhian-surface calculations.Öğe In-beam gamma-ray spectroscopy of the N=85 isotones W-159 and Re-160(AMER PHYSICAL SOC, 2011) Sapple, P. J.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Pakarinen, J.; Julin, R.Excited states have been identified in the isotones W-159(74) and Re-160(75), which were produced in fusion-evaporation reactions of a beam of 310-MeV Ni-58 ions with an isotopically enriched Cd-106 target. The strongest gamma-ray transitions in W-159 and Re-160 are interpreted as continuing the regular sequence of states identified in lighter N = 85 isotones that are built upon 9/2(-) and 10(+) states, respectively. The half-life of Hf-155, the beta-decaying daughter of the a decay of W-159, was measured with improved precision to be 840 +/- 30 ms.Öğe Isomeric and ground-state properties of Pt-171(78), Os-167(76), and W-163(74)(AMER PHYSICAL SOC, 2010) Scholey, C.; Andgren, K.; Bianco, L.; Cederwall, B.; Darby, I. G.; Eeckhaudt, S.; Joss, D. T.Decay paths, half-lives, and excitation energies of the i(13/2) bandheads of the neutron-deficient nuclei Pt-171, Os-167, and W-163 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 nu f(7/2), nu h(9/2), and nu i(13/2) quasineutron states for all three nuclei. Moreover, ground-state spin assignments have been made for the first time, along with the measurement of the alpha-decay branching ratio for Pt-171. The decay paths of the i(13/2) bandheads were followed by favored alpha decays, indicating that all three nuclei have the same I-pi = 7/2(-) ground state.Öğe Precision measurements of proton emission from the ground states of Ta-156 and Re-160(AMER PHYSICAL SOC, 2011) Darby, I. G.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Judson, D. S.; Leino, M.The decays of the pi d(3/2) ground states of Ta-156 and Re-160 have been studied in detail using the GREAT spectrometer. More than 7000 Re-160 nuclei were produced in reactions of 290- and 300-MeV Ni-58 ions with an isotopically enriched Cd-106 target and separated in flight using the RITU separator. The proton and alpha decays of the pi d(3/2) level were confirmed and the half-life and branching ratios of this state were determined with improved precision to be t(1/2) = 611 +/- 7 mu s and b(p) = 89 +/- 1% and b(alpha) = 11 +/- 1%, respectively. The alpha-decay branch populated the ground state of Ta-156, allowing improved values for the proton-decay energy and half-life to be obtained (E-p = 1011 +/- 5 keV; t(1/2) = 106 +/- 4 ms). The beta decay of this level was identified for the first time and a branching ratio of b(beta) = 29 +/- 3% was deduced. The spectroscopic factors deduced from these measurements are compared with predictions.Öğe Probing single-particle structures beyond the proton drip line(AMER INST PHYSICS, 2007) Page, R. D.; Bianco, L.; Darby, I. G.; Joss, D. T.; Grahn, T.; Herzberg, R. -D.; Juutinen, S.; Ferreira, LS; Arumugam, PSingle-particle energies have been investigated in the closed neutron shell proton emitter Ta-155. The Ta-155 nuclei were populated through the alpha decay of Re-159, which has been observed for the first time. The (159)Rc nuclei were produced in reactions of 300 MeV Ni-58 ions with an isotopically enriched Cd-106 target, separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The Re-159 a decay emanates from the proton-emitting pi h(11/2) state and populates a state in Ta-155 which decays by the emission of a proton from a pi h(11/2) orbital. The results fit in with the systematics of proton and alpha-particle separation energies in the region, but disagree with the previously reported decay properties of Ta-155.
