| 1. |
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| 2. |
- Andreyev, A. N., et al.
(författare)
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In-beam and alpha-decay spectroscopy of Po-191 and evidence for triple shape coexistence at low energy in the daughter nucleus Pb-187
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 66:1
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Tidskriftsartikel (refereegranskat)abstract
- Prompt gamma rays have been observed for the first time from the neutron-deficient nucleus Po-191 using the recoil-decay tagging technique at the RITU gas-filled separator. In addition improved alpha decay data have been measured for Po-191 and its daughter product Pb-187. The complementary gamma- and alpha-decay data point to the onset of oblate deformation in the light odd-mass Po nuclei by approaching the neutron midshell at N=104. The pattern of the favored and unfavored states observed on top of the 13/2(+) isomer in Po-191 indicates a change from the weak-coupling towards the strong-coupling scheme in Po-191m. In the daughter nucleus Pb-187, the 13/2(+) and 3/2(-) isomeric states become degenerate within the experimental accuracy. Evidence for triple shape coexistence at low energy has been found in the high-spin isomer in Pb-187. The results are supported by potential-energy surface calculations and by particle-plus-rotor calculations.
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| 3. |
- Van de Vel, K., et al.
(författare)
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Identification of low-lying proton-based intruder states in Pb189-193
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 65:6
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Tidskriftsartikel (refereegranskat)abstract
- Low-lying proton-based intruder states have been observed in the odd-mass isotopes Pb-189,Pb-191,Pb-193 in experiments at the RITU gas-filled recoil separator. The identification has been performed by observing the fine structure in the alpha decay of the parent Po-193,Po-195,Po-197 nuclei in prompt coincidence with conversion electrons and gamma rays in the daughter lead isotopes. Along with the literature data these results establish a systematics of intruder states in the odd-mass lead isotopes from Pb-197 down to Pb-185. Interpretation of these states involves the coupling of the 1i(13/2) or 3p(3/2) odd neutron to the 0(+) state in the oblate minimum in the even-mass lead core. Conversion coefficients have been determined for some of the transitions, revealing mixing between the coexisting states. The experimental results are compared to potential energy surface calculations.
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| 4. |
- Bergmann, U. C., et al.
(författare)
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Beta-decay properties of the neutron-rich Kr94-99 and Xe142-147 isotopes
- 2003
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Ingår i: Nuclear Physics A. - 0375-9474. ; 714:1-2, s. 21-43
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Tidskriftsartikel (refereegranskat)abstract
- Beta-decay half-lives and delayed-neutron emission probabilities of the neutron-rich noble-gas isotopes Kr94-99 and Xe142-147 have been measured at the PSB-ISOLDE facility at CERN. The results are compared to QRPA shell-model predictions and are used in dynamic calculations of r-process abundances of Kr and Xe isotopes. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 5. |
- Van De Vel, K., et al.
(författare)
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In-beam gamma-ray spectroscopy of Po-190 : First observation of a low-lying prolate band in Po isotopes
- 2003
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 17:2, s. 167-171
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Tidskriftsartikel (refereegranskat)abstract
- Gamma rays from excited states of Po-190 have been observed using I the Jurosphere Ge-detector array coupled to the RITU gas-filled separator. They were associated with a collective band which from spin 4h onwards resembles the prolate rotational bands known in the isotones Pb-188 and Hg-186. This indicates that in Po-190 the prolate configuration becomes yrast above I = 2h. The experimental results are interpreted in a two-band mixing calculation and are in agreement with a-decay data and potential energy surface calculations.
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| 6. |
- Andreyev, A. N., et al.
(författare)
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Shape-changing particle decays of Bi-185 and structure of the lightest odd-mass Bi isotopes
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69:5, s. 054308-
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Tidskriftsartikel (refereegranskat)abstract
- Proton and alpha decay of the proton-rich nuclide Bi-185 has been restudied in more detail in the complete fusion reaction Nb-93(Mo-95, 3n)Bi-185 at the velocity filter SHIP. The observed decay pattern of Bi-185 and of the heavier odd-mass isotopes Bi-187,Bi-189,Bi-191,Bi-193 are interpreted based on potential-energy surface calculations. It is shown that the experimental systematics of the particle decays and of the excited states in these nuclei (where known) can be explained by the prolate-oblate shape co-existence at low excitation energy. The observed state in Bi-185 is proposed to be of prolate nature, which is in contrast with the previously proposed oblate interpretation.
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| 7. |
- Huyse, M., et al.
(författare)
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Anomalies in the alpha-decay energies and half-lives of neutron-deficient Po isotopes
- 2001
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Ingår i: Hyperfine Interactions. - 0304-3843 .- 1572-9540. ; 132:04-jan, s. 141-146
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Tidskriftsartikel (refereegranskat)abstract
- The transition rates of DeltaL = 0 alpha transitions in them lightest Po isotopes are considerably slower than the transition rates of the heavier ones, even leading to a considerable deviation in the classical Geiger-Nuttall plot. Evidence will be given that due to particle-hole excitations through the Z = 82 proton shell, the groundstate of the lighter Po isotopes becomes deformed and direct alpha decay to the spherical groundstate of the corresponding Ph isotopes is highly retarded.
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| 8. |
- Joss, D. T., et al.
(författare)
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Yrast states and band crossings in the neutron-deficient platinum isotopes Pt169-173
- 2006
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 74:1
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Tidskriftsartikel (refereegranskat)abstract
- The yrast states in the light platinum isotopes Pt169-173 have been investigated in a recoil-decay tagging experiment using the JUROGAM gamma-ray spectrometer in conjunction with the RITU gas-filled recoil separator and the GREAT tagging spectrometer. Gamma-ray transitions have been established for the first time in the odd-N isotopes, Pt-169 and Pt-173, and the yrast sequences in Pt-170 and Pt-172 have been extended. We discuss the possibility that the weakly deformed yrast structures of Pt-170, Pt-172, and Pt-173 are crossed by a deformed intruder configuration at spin similar to 8h.
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| 9. |
- Karlgren, Daniel, et al.
(författare)
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Alpha-decay hindrance factors : A probe of mean-field wave function
- 2006
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 73:6, s. 064304-
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Tidskriftsartikel (refereegranskat)abstract
- A simple model to calculate alpha-decay hindrance factors (HF) with special emphasis on the shape coexistence in the Pb-Po region is presented. Using deformation values obtained from potential energy surface (PES) calculations as the only input, hindrance factors for the alpha decay of Rn and Po isotopes are calculated. The fair agreement between experimental and theoretical hindrance factors suggest that the wave function obtained from the energy minima of the PES calculations contains an important part of the correlations that play a role for the alpha decay. The model is applicable to shape coexistence in the Po and Pb region when minima are well defined. The calculated HF that emerge from these calculations render a different interpretation than the commonly assumed n-particle n-hole picture of the intruder states in the Pb region.
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| 10. |
- Van de Vel, K., et al.
(författare)
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Fine structure in the alpha decay of Po-188,Po-192
- 2003
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 68:5
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Tidskriftsartikel (refereegranskat)abstract
- The alpha decay of Po-188,Po-192 has been reexamined in order to probe the 0(+) states in the daughter nuclei Pb-184,Pb-188 that can be associated with coexisting spherical, oblate, and/or prolate configurations. Improved values were measured for the excitation energy and the feeding alpha -decay intensity of the 0(2)(+) state in Pb-184,Pb-188 and conflicting results on the 0(3)(+) state in Pb-188 were clarified. All known cases of fine structure in the alpha decay of the even-even Po nuclei are reviewed. The reduced alpha-decay width systematics combined with potential-energy-surface calculations confirm the onset of deformation in the ground state of the polonium nuclei around the neutron midshell. An isomeric state with a half-life of 580(100)ns has been identified in Po-192 .
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| 11. |
- Van de Vel, K., et al.
(författare)
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Prolate structures in Po-189 and Pb-185
- 2005
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 24:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The 3/2(-) isomer in Pb-185 and states above it have been populated in the α-decay of Po-189. The observed α-decay strengths to and the electromagnetic decay properties of the excited states in Pb-185 have been combined with Potential Energy Surface and Particle-Plus-Rotor calculations to propose configuration assignments. It is suggested that the α-decaying isomer of Po-189 is of prolate origin and that the prolate configuration becomes very low in energy in Pb-185.
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| 12. |
- Joss, D. T., et al.
(författare)
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Yrast structures in the light Pt isotopes Pt169-173
- 2005
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1715-S1718
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Tidskriftsartikel (refereegranskat)abstract
- The exploitation of the recoil-decay tagging (RDT) technique has reinvigorated experimental investigations of the shape coexistence phenomenon in heavy neutron-deficient nuclei. In a recent experiment using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator, excited states have been investigated in the light platinum isotopes. In addition to extending the yrast sequences in Pt-170 and Pt-172, the first observation of excited states in the odd-N isotopes, Pt-169 and Pt-173, is reported. The bands are discussed in terms of trends in level excitation energies as a function of neutron number.
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| 13. |
- Scholey, C., et al.
(författare)
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In-beam and decay spectroscopy of very neutron deficient iridium nuclei
- 2005
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1719-S1722
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Tidskriftsartikel (refereegranskat)abstract
- Iridium nuclei at and beyond the proton drip line have been studied via fusion evaporation reactions. A reaction of Mo-92(Kr-78, p2n) at a beam energy of 360 MeV and target thickness 500 mu g cm(-2) was employed to study (167,167m) Ir. A reaction of Sn-112(Ni-58, p2n) at a beam energy of 266 MeV and target thickness 500 mu g cm(-2) was used to study (169,169m) Ir. The experiments were performed at the University of Jyvaskyla utilizing the RITU separator in conjunction with the focal plane GREAT spectrometer and the JUROGAM Ge array at the target position. Excited states feeding. both the ground state and isomeric state in Ir-169, excited states feeding the ground state of Ir-167 and the ground state alpha decay of Re-165 have been observed for the first time along with excited states feeding (167)m Ir Experimental spectroscopic factors and reduced widths have been obtained for the proton and alpha decay of these nuclei.
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