| 1. |
- 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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| 2. |
- Bäck, Torbjörn, et al.
(författare)
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First observation of gamma-rays from the proton emitter Au-171
- 2003
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 16:4, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-rays from the alpha- and proton-unstable nuclide Au-171 have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2(-)) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.
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| 3. |
- Bäck, Torbjörn, et al.
(författare)
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Spectroscopy of the neutron-deficient nuclide Pt-171
- 2003
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 17:1, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using information from gamma-gamma coincidences and angular distribution measurements. To further confirm the assignments of the gamma-rays to Pt-171, the events were correlated with the alpha-decay of the daughter nucleus Os-167.
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| 4. |
- 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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| 5. |
- Nieminen, P., et al.
(författare)
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gamma-ray spectroscopy of Bi-191,Bi-193
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69:6, s. 064326-
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Tidskriftsartikel (refereegranskat)abstract
- Prompt and delayed gamma rays from Bi-191,Bi-193 have been identified using the recoil-decay tagging, isomer tagging, and recoil gating techniques, resulting in extensive level schemes for both nuclei. Excitation energies of the isomeric 13/2(+) states have been established and oblate strongly coupled bands built on them have been observed. The nearly spherical 9/2(-) ground-state bands appear to be crossed by more oblate-deformed low-lying structures. The properties of the bands feeding the 1/2(+) intruder states indicate some structural change between Bi-193 and Bi-191. The deformation associated with each of these states has been extracted from total Routhian surface calculations which also reveal the development of prolate minima with decreasing neutron number. B(M1)/B(E2) ratios have been measured for the observed strongly coupled bands in order to resolve the intrinsic excitations. The observed quasiparticle structures in Bi-193 and high-spin isomers both in Bi-193 and Bi-191 are interpreted based on the coupling of the odd proton to the even-even Pb core.
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| 6. |
- 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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| 7. |
- Bark, R A, et al.
(författare)
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Coexistence of triaxial and prolate shapes in Ir-171
- 1999
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 657:2, s. 113-133
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in Ir-171 have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method, The ground-state band has a structure consistent with an h(11/2) proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation, Band-mixing calculations are performed for Ir171-175. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for Ir171-179 using the code "Ultimate Cranker". Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.
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| 8. |
- King, S L, et al.
(författare)
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First observation of excited states in the neutron deficient nuclei (PT)-P-168 and Pt-170
- 1998
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 443:1-4, s. 82-88
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Tidskriftsartikel (refereegranskat)abstract
- Excited states have been observed for the first time in (XPt)-X-168 and Pt-170 using the alpha-decay recoil-tagging technique. The trend of decreasing deformation moving away from the N = 104 mid-shell continues far Pt-170 but the structure of Pt-168 is significantly different. The low spin level energy systematics in Pt168-184 are presented and discussed within the framework of the interacting boson model. (C) 1998 Elsevier Science B.V. All rights reserved.
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| 9. |
- Kirsebom, O. S., et al.
(författare)
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Measurement of the 2+→0+ ground-state transition in the β decay of F 20
- 2019
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Ingår i: Physical Review C. - 2469-9985. ; 100:6
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Tidskriftsartikel (refereegranskat)abstract
- We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of F20. A low-energy, mass-separated F+20 beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plastic-scintillator detector. The β-decay branching ratio inferred from the measurement is bβ=[0.41±0.08(stat)±0.07(sys)]×10-5 corresponding to logft=10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on Ne20 is now known to within better than 25% at the relevant temperatures and densities.
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| 10. |
- Andreyev, A. N., et al.
(författare)
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alpha-decay of the new isotope Po-187 : Probing prolate structures beyond the neutron mid-shell at N=104
- 2006
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 73:4, s. 044324-
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Tidskriftsartikel (refereegranskat)abstract
- The new neutron-deficient isotope Po-187 has been identified in the complete fusion reaction Ti-46+Sm-144 -> Po-187+3n at the velocity filter SHIP. Striking features of the Po-187 alpha decay are the strongly-hindered decay to the spherical ground state and unhindered decay to a surprisingly low-lying deformed excited state at 286 keV in the daughter nucleus Pb-183. Based on the potential energy surface calculations, the Po-187 ground state and the 286 keV excited state in Pb-183 were interpreted as being of prolate origin. The systematic deviation of the alpha-decay properties in the lightest odd-A Po isotopes relative to the smooth behavior in the even-A neighbors is discussed. Improved data for the decay of Bi-187(m,g) were also obtained.
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