| 1. |
- Barzakh, A., et al.
(author)
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Large Shape Staggering in Neutron-Deficient Bi Isotopes
- 2021
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In: Physical Review Letters. - 0031-9007. ; 127:19
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Journal article (peer-reviewed)abstract
- The changes in the mean-square charge radius (relative to Bi209), magnetic dipole, and electric quadrupole moments of Bi187,188,189,191 were measured using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). A large staggering in radii was found in Bi187,188,189g, manifested by a sharp radius increase for the ground state of Bi188 relative to the neighboring Bi187,189g. A large isomer shift was also observed for Bi188m. Both effects happen at the same neutron number, N=105, where the shape staggering and a similar isomer shift were observed in the mercury isotopes. Experimental results are reproduced by mean-field calculations where the ground or isomeric states were identified by the blocked quasiparticle configuration compatible with the observed spin, parity, and magnetic moment. © 2021 authors.
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| 2. |
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| 3. |
- Butler, P. A., et al.
(author)
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Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive ^{222}Ra and ^{228}Ra Beams
- 2020
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In: Physical Review Letters. - 1079-7114. ; 124:4
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Journal article (peer-reviewed)abstract
- There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
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| 4. |
- Butler, P. A., et al.
(author)
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The observation of vibrating pear-shapes in radon nuclei
- 2019
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Journal article (peer-reviewed)abstract
- There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in 224Rn and 226Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.
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| 5. |
- Spagnoletti, P., et al.
(author)
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Coulomb excitation of Rn 222
- 2022
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In: Physical Review C. - 2469-9985. ; 105:2
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Journal article (peer-reviewed)abstract
- The nature of quadrupole and octupole collectivity in Rn222 was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive Rn222 beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, Sn120 and Ni60. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3- and 2+→5- transitions were found to be respectively 2360-210+300efm3 and 2300-500+300efm3 while a smaller value, 1200-900+500efm3, was found for the 2+→1- transition. In addition, four excited non-yrast states were identified in this work via γ-γ coincidences.
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| 6. |
- Stryjczyk, M., et al.
(author)
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Decay studies of the long-lived states in Tl 186
- 2020
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In: Physical Review C. - 2469-9985. ; 102:2
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Journal article (peer-reviewed)abstract
- Decay spectroscopy of the long-lived states in Tl186 has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The α decay from the low-spin (2-) state in Tl186 was observed for the first time and a half-life of 3.4-0.4+0.5 s was determined. Based on the α-decay energy, the relative positions of the long-lived states were fixed, with the (2-) state as the ground state, the 7(+) state at 77(56) keV, and the 10(-) state at 451(56) keV. The level scheme of the internal decay of the Tl186(10(-)) state [T1/2=3.40(9) s], which was known to decay solely through emission of 374-keV γ-ray transition, was extended and a lower limit for the β-decay branching bβ>5.9(3)% was determined. The extracted retardation factors for the γ decay of the 10(-) state were compared to the available data in neighboring odd-odd thallium isotopes indicating the importance of the πd3/2 shell in the isomeric decay and significant structure differences between Tl184 and Tl186.
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| 7. |
- Stryjczyk, M., et al.
(author)
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Simultaneous γ -ray and electron spectroscopy of Hg 182,184,186 isotopes
- 2023
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In: Physical Review C. - 2469-9985. ; 108:1
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Journal article (peer-reviewed)abstract
- Background: The mercury isotopes around N=104 are a well-known example of nuclei exhibiting shape coexistence. Mixing of configurations can be studied by measuring the monopole strength ρ2(E0), however, currently the experimental information is scarce and lacks precision, especially for the Iπ→Iπ (I≠0) transitions. Purpose: The goals of this study were to increase the precision of the known branching ratios and internal conversion coefficients, to increase the amount of available information regarding excited states in Hg182,184,186, and to interpret the results in the framework of shape coexistence using different models. Method: The low-energy structures in Hg182,184,186 were populated in the β decay of Tl182,184,186, produced at ISOLDE, CERN and purified by laser ionization and mass separation. The γ-ray and internal conversion electron events were detected by five germanium clover detectors and a segmented silicon detector, respectively, and correlated in time to build decay schemes. Results: In total, 193, 178, and 156 transitions, including 144, 140, and 108 observed for the first time in a β-decay experiment, were assigned to Hg182,184,186, respectively. Internal conversion coefficients were determined for 23 transitions, out of which 12 had an E0 component. Extracted branching ratios allowed the sign of the interference term in Hg182 as well as ρ2(E0;02+→01+) and B(E2;02+→21+) in Hg184 to be determined. By means of electron-electron coincidences, the 03+ state was identified in Hg184. The experimental results were qualitatively reproduced by five theoretical approaches, the interacting boson model with configuration mixing with two different parametrizations, the general Bohr Hamiltonian, the beyond mean-field model, and the symmetry-conserving configuration-mixing model. However, a quantitative description is lacking. Conclusions: The presence of shape coexistence in neutron-deficient mercury isotopes was confirmed and evidence for the phenomenon existing at higher energies was found. The new experimental results provide important spectroscopic input for future Coulomb excitation studies. © 2023 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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