| 11. |
- Andel, B., et al.
(författare)
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β -delayed fission of isomers in Bi 188
- 2020
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Ingår i: Physical Review C. - 2469-9985. ; 102:1
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Tidskriftsartikel (refereegranskat)abstract
- β-delayed fission (βDF) decay of a low-spin (ls) and a high-spin (hs) isomer in Bi188 was studied at the ISOLDE facility at CERN. Isomer-selective laser ionization and time gating were employed to investigate each isomer separately and their βDF partial half-lives were determined: T1/2p,βDF(188Bihs)=5.6(8)×103 s and T1/2p,βDF(188Bils)=1.7(6)×103 s. This work is the first βDF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide Pb188, following the β decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes. Experimental results were compared with self-consistent mean-field calculations based on the finite-range Gogny D1M interaction. To reproduce the measured T1/2p,βDF(188Bihs), the calculated fission barrier of Pb188 had to be reduced by ≈30%. After this reduction, the measured T1/2p,βDF(188Bils) was in agreement with calculations for a few possible configurations for Bils188. Theoretical βDF probabilities for these configurations were found to be lower by a factor of 4-9 than the βDF probability of Bihs188. The fission fragment mass distribution of Pb188 was compared to the scission-point model SPY and the calculations based on the finite-range liquid-drop model. The first observation of βDF for Bi190 is also reported. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
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| 12. |
- Cocolios, T. E., et al.
(författare)
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Structure of Pb-191 from alpha- and beta-decay spectroscopy
- 2010
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 37:12, s. 125103-
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Tidskriftsartikel (refereegranskat)abstract
- Complementary studies of Pb-191 have been made in the beta decay of Bi-191 at LISOL (CRC) and in the alpha decay of Po-195 at ISOLDE (CERN). Fine structures in the alpha decay of the low-spin and high-spin isomers of 195Po have been fully resolved. Identification of the parent state is made possible via isomer selection based on narrow-band laser frequency scanning. The alpha-particle and gamma-ray energies have been determined with greater precision. New alpha-particle and. gamma-ray energies are identified. Branching ratios in the decay of Po-195 and Pb-191 have been examined.
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| 13. |
- Fedosseev, V. N., et al.
(författare)
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Ionization scheme development at the ISOLDE RILIS
- 2005
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 162:1-4, s. 15-27
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Tidskriftsartikel (refereegranskat)abstract
- The resonance ionization laser ion source (RILIS) of the ISOLDE on-line isotope separation facility is based on the method of laser step-wise resonance ionization of atoms in a hot metal cavity. The atomic selectivity of the RILIS complements the mass selection process of the ISOLDE separator magnets to provide beams of a chosen isotope with greatly reduced isobaric contamination. Using a system of dye lasers pumped by copper vapour lasers, ion beams of 24 elements have been generated at ISOLDE with ionization efficiencies in the range of 0.5-15%. As part of the ongoing RILIS development off-line resonance ionization spectroscopy studies carried out in 2003 and 2004 have determined the optimal three-step ionization schemes for scandium, antimony, dysprosium and yttrium.
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| 14. |
- Fedosseev, V. N., et al.
(författare)
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Upgrade of the resonance ionization laser ion source at ISOLDE on-line isotope separation facility : New lasers and new ion beams
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:2, s. 02A903-
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Tidskriftsartikel (refereegranskat)abstract
- The resonance ionization laser ion source (RILIS) produces beams for the majority of experiments at the ISOLDE on-line isotope separator. A substantial improvement in RILIS performance has been achieved through a series of upgrade steps: replacement of the copper vapor lasers by a Nd:YAG laser; replacement of the old homemade dye lasers by new commercial dye lasers; installation of a complementary Ti:Sapphire laser system. The combined dye and Ti:Sapphire laser system with harmonics is capable of generating beams at any wavelength in the range of 210-950 nm. In total, isotopes of 31 different elements have been selectively laser-ionized and separated at ISOLDE, including recently developed beams of samarium, praseodymium, polonium, and astatine.
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| 15. |
- Gaffney, L. P., et al.
(författare)
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Low-energy Coulomb excitation of 62Fe and 62Mn following in-beam decay of 62Mn
- 2015
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:10, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Sub-barrier Coulomb excitation was performed on a mixed beam of 62Mn and 62Fe, following in-trap β− decay of 62Mn at REX-ISOLDE, CERN. The trapping and charge breeding times were varied in order to alter the composition of the beam, which was measured by means of an ionisation chamber at the zero-angle position of the Miniball array. A new transition was observed at 418 keV, which has been tentatively associated to a (2+,3+)→ 1g.s. + transition. This fixes the relative positions of the β-decaying 4+ and 1+ states in 62Mn for the first time. Population of the 21 + state was observed in 62Fe and the cross-section determined by normalisation to the 109Ag target excitation, confirming the B(E2) value measured in recoil-distance lifetime experiments.
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| 16. |
- Marsh, B. A., et al.
(författare)
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The ISOLDE RILIS pump laser upgrade and the LARIS Laboratory
- 2010
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Ingår i: Hyperfine Interactions. - : Springer Nature. - 0304-3843 .- 1572-9540. ; 196:1-3, s. 129-141
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Tidskriftsartikel (refereegranskat)abstract
- On account of its high efficiency, speed and unmatched selectivity, the Resonance Ionization Laser Ion Source (RILIS) is the preferred method for ionizing the nuclear reaction products at the ISOLDE on-line isotope separator facility. By exploiting the unique electronic energy level 'fingerprint' of a chosen element, the RILIS process of laser step-wise resonance ionization enables an ion beam of high chemical purity to be sent through the mass selective separator magnet. The isobaric purity of a beam of a chosen isotope is therefore greatly increased. The RILIS, comprising of up to three frequency tunable pulsed dye lasers has been upgraded with the installation of a Nd:YAG pump laser as a replacement for the old Copper Vapor Laser (CVL) system. A summary of the current Nd:YAG pumped RILIS performance is given. To accompany the RILIS pump laser upgrade, a new ionization scheme for manganese has been developed at the newly constructed LAser Resonance Ionization Spectroscopy (LARIS) laboratory and successfully applied for on-line RILIS operation. An overview of the LARIS facility is given along with details of the ionization scheme development work for manganese.
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| 17. |
- Pauwels, D., et al.
(författare)
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Gamow-Teller decay population of Ni-64 levels in the decay of 1(+) Co-64
- 2012
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 86:6, s. 064318-
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Tidskriftsartikel (refereegranskat)abstract
- The Co-64 beta-decay feeding levels in the well-studied Ni-64 nucleus were investigated. Whereas the previously known Co-64 decay scheme merely contained 2 gamma rays, the decay scheme established in this work contains 18, of which 5 are observed in this work and 6 were previously observed in an (n, gamma) study but not placed in the Ni-64 level scheme. Surprisingly, one additional level-placed at an excitation energy of 3578.7 keV-could be determined. The observed beta-decay paths involve allowed nu f(5/2) -> pi f(7/2) and nu p(1/2) -> pi p(3/2) transitions. Three strongly fed levels around 4 MeV are interpreted to possess possible proton-intruder character.
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| 18. |
- Radulov, D., et al.
(författare)
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beta decay of Mn-61 to levels in Fe-61
- 2013
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 88:1, s. 014307-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed beta-decay study of Mn-61 is presented, yielding extended information on the level structure of Fe-61. Pure beams were obtained at ISOLDE, CERN, after selective laser ionization and mass separation of fission products from the bombardment of a UCx target by 1.4-GeV protons. The beta and gamma information was detected by two MiniBall clusters and three Delta E plastic scintillators. The new Mn-61 decay scheme reveals 48 gamma transitions, distributed over 20 excited states. A comparison to the decay scheme of Mn-59 and excited states in Fe-59 is made. Shell-model calculations with two different interactions are performed in order to compare the nuclear structure of the two neighboring odd-A iron isotopes. Tentative spin and parities of several excited states in Fe-61 are assigned on the basis of beta-decay feeding patterns in both Fe-59,Fe-61 and of results from the theoretical shell-model calculations.
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| 19. |
- Seliverstov, M. D., et al.
(författare)
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Electromagnetic moments of odd-A Po-193-203,Po-211 isotopes
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:3, s. 034323-
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Tidskriftsartikel (refereegranskat)abstract
- Hyperfine splitting parameters have been measured for the neutron-deficient odd-mass polonium isotopes and isomers Po-193-203(g,m), Po-209,Po-211. The measurement was performed at the ISOLDE (CERN) online mass separator using the in-source resonance ionization spectroscopy technique. The magnetic dipole moments mu and spectroscopic electric quadrupole moments Q(S) have been deduced. Their implication for the understanding of nuclear structure in the vicinity of the closed proton shell at Z = 82 and the neutron mid-shell at N = 104 is discussed. For the most neutron-deficient nuclei (A = 193,195,197), a deviation of mu and QS from the nearly constant values for heavier polonium nuclei was observed. Particle-plus-rotor calculations with static oblate deformation describe the electromagnetic moments for these nuclei well, provided a gradual increase of a mean deformation when going to lighter masses is assumed for the polonium nuclei with A < 198.
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| 20. |
- Stefanescu, I, et al.
(författare)
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Interplay between single-particle and collective effects in the odd-A Cu isotopes beyond N=40
- 2008
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Ingår i: Physical Review Letters. - 1079-7114. ; 100:11
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Tidskriftsartikel (refereegranskat)abstract
- Collective properties of the low-lying levels in the odd-A Cu67-73 were investigated by Coulomb excitation with radioactive beams. The beams were produced at ISOLDE and postaccelerated by REX-ISOLDE up to 2.99 MeV/u. In Cu-67,Cu-69, low-lying 1/2(-), 5/2(-), and 7/2(-) states were populated. In Cu-71,Cu-73, besides the known transitions deexciting the single-particle-like 5/2(-) and core-coupled 7/2(-) levels, gamma rays of 454 and 135 keV, respectively, were observed for the first time. Based on a reanalysis of beta-decay work and comparison with the systematics, a spin 1/2(-) is suggested for these excited states. Three B(E2) values were determined in each of the four isotopes. The results indicate a significant change in the structure of the odd-A Cu isotopes beyond N=40 where single-particle-like and collective levels are suggested to coexist at very low excitation energies.
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