Yazar "Darby, I. G." seçeneğine göre listele
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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 the proton emitting nucleus Re-159(AMER INST PHYSICS, 2007) Joss, D. T.; Darby, I. G.; Page, R. D.; Uttsitalo, J.; Eeckhaudt, S.; Grahn, T.; Nyman, A.; Ferreira, LS; Arumugam, PThe observation of the new nuclide Re-159 provides important insights into the evolution of single-particle structure in heavy nuclei beyond the proton drip line. The nuclide Re-159 was synthesised in the reaction Cd-106(Ni-58, p4n) and identified via its proton radioactivity using the RITU gas-filled separator and the GREAT focal-plane spectrometer. Comparisons of the measured proton energy (E-p = 1805 +/- 20 keV) and decay half-life (t(1/2) = 21 +/- 4 ps) with values calculated using the YIKB method indicate that the proton is emitted from an h(11/2) state. The implications of these results for future experimental investigations into even more proton unbound Re isotopes using in-flight separation techniques are considered.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 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.Öğe Probing the limit of nuclear existence: Proton emission from Re-159(ELSEVIER SCIENCE BV, 2006) Joss, D. T.; Darby, I. G.; Page, R. D.; Uusitalo, J.; Eeckhaudt, S.; Grahn, T.; Nyman, M.The observation of the new nuclide Re-159(75)84 provides important insights into the evolution of single-particle structure and the mass surface in heavy nuclei beyond the proton drip line. This nuclide, 26 neutrons away from the nearest stable rhenium isotope, was synthesised in the reaction Cd-106(Ni-58, p4n) and identified via its proton radioactivity using the RITU gas-filled separator and the GREAT focal-plane spectrometer. Comparisons of the measured proton energy (E-p = 1805 +/- 20 keV) and decay half-life (t(1/2) = 21 +/- 4 mu s) with values calculated using the WKB method indicate that the proton is emitted from an h(11/2) state. The implications of these results for future experimental investigations into even more proton unbound nuclei using in-flight separation techniques are considered. (c) 2006 Elsevier B.V. All rights reserved.
