| 1. |
- Bree, N, et al.
(författare)
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Shape Coexistence in the Neutron-Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation.
- 2014
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Ingår i: Physical Review Letters. - 1079-7114. ; 112:16
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Tidskriftsartikel (refereegranskat)abstract
- Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.
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| 2. |
- Wrzosek-Lipska, K., et al.
(författare)
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Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes : Coulomb excitation of 182Hg, 184Hg, 186Hg and 188Hg
- 2019
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 55:8
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Tidskriftsartikel (refereegranskat)abstract
- The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass 182-188 Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 01,2+, 21,2+ and 41+ states was observed in all nuclei under study. Reduced E2 matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
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| 3. |
- Gaffney, L. P., et al.
(författare)
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Collectivity in the light radon nuclei measured directly via Coulomb excitation
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around Z = 82 and the neutron midshell at N = 104. Purpose: Evidence for shape coexistence has been inferred from a-decay measurements, laser spectroscopy, and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of Rn-202 and Rn-204 were studied by means of low-energy Coulomb excitation at the REX-ISOLDE in CERN. Results: The electric-quadrupole (E2) matrix element connecting the ground state and first excited 2(1)(+) state was extracted for both Rn-202 and Rn-204, corresponding to B(E2; 2(1)(+) -> 0(1)(+)) = 29(-8)(+8) and 43(-12)(+17) W.u., respectively. Additionally, E2 matrix elements connecting the 2(1)(+) state with the 4(1)(+) and 2(2)(+) states were determined in Rn-202. No excited 0(+) states were observed in the current data set, possibly owing to a limited population of second-order processes at the currently available beam energies. Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
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| 4. |
- Vogt, A., et al.
(författare)
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Isomers and high-spin structures in the N=81 isotones Xe-135 and Ba-137
- 2017
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Ingår i: PHYSICAL REVIEW C. - : AMER PHYSICAL SOC. - 2469-9985. ; 95:2
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Tidskriftsartikel (refereegranskat)abstract
- The high-spin structures and isomers of the N = 81 isotones Xe-135 and Ba-137 are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in Xe-136+ U-238 and (ii) Xe-136+ Pb-208 MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii) in the Xe-136+ Pt-198 MNT reaction employing the gamma-ray array GAMMASPHERE in combination with the gas-detector array CHICO, and (iv) via a B-11+ Te-130 fusion-evaporation reaction with the HORUS gamma-ray array at the University of Cologne. The high-spin level schemes of Xe-135 and Ba-137 are considerably extended to higher energies. The 2058-keV (19/2(-)) state in Xe-135 is identified as an isomer, closing a gap in the systematics along the N = 81 isotones. Its half-life is measured to be 9.0(9) ns, corresponding to a reduced transition probability of B(E2,19/2(-) -> 15/2(-)) = 0.52(6) W.u. The experimentally deduced reduced transition probabilities of the isomeric states are compared to shell-model predictions. Latest shell-model calculations reproduce the experimental findings generally well and provide guidance to the interpretation of the new levels.
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| 5. |
- Blazhev, A, et al.
(författare)
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High-energy excited states in 98 Cd
- 2010
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Ingår i: Journal of Physics: Conference Series. ; 205:1
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Tidskriftsartikel (refereegranskat)abstract
- In 98 Cd a new high-energy isomeric γ -ray transition was identified, which confirms previous spin-parity assignments and enables for the first time the measurement of the E 2 and E 4 strength for the two decay branches of the isomer. Preliminary results on the 98 Cd high-excitation level scheme are presented. A comparison to shell-model calculations as well as implications for the nuclear structure around 100 Sn are discussed.
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| 6. |
- Boutachkov, P., et al.
(författare)
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High-spin isomers in 96Ag : excitations across the Z=38 and Z=50, N=50 closed shells
- 2011
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 84:4
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in (96)Ag were populated in fragmentation of an 850-MeV/u (124)Xe beam on a 4-g/cm(2) Be target. Three new high-spin isomers were identified and the structure of the populated states was investigated. The level scheme of (96)Ag was established, and a spin parity of (13(-)), (15(+)), and (19(+)) was assigned to the new isomeric states. Shell-model calculations were performed in various model spaces, including pi nu(p(1/2), g(9/2), f(5/2), p(3/2)) and the large-scale shell-model space pi nu(gds), to account for the observed parity changing M2 and E3 transitions from the (13(-)) isomer and the E2 and E4 transitions from the (19(+)) core-excited isomer, respectively. The calculated level schemes and reduced transition strengths are found to be in very good agreement with the experiment.
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| 7. |
- DiJulio, Douglas, et al.
(författare)
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Coulomb excitation of In-107
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:1
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Tidskriftsartikel (refereegranskat)abstract
- The radioactive isotope In-107 was studied using sub-barrier Coulomb excitation at the REX-ISOLDE facility at CERN. Two gamma rays were observed during the experiment, corresponding to the low-lying 11/2(+) and 3/2(-)states. The reduced transition probability of the 11/2(+) state was determined with the semiclassical Coulomb excitation code GOSIA2. The result is discussed in comparison to large-scale shell-model calculations, previous unified-model calculations, and earlier Coulomb excitation measurements in the odd-mass In isotopes. DOI: 10.1103/PhysRevC.87.017301
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| 8. |
- Ekström, Andreas, et al.
(författare)
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Electric quadrupole moments of the 2(1)(+) states in Cd-100,Cd-102,Cd-104
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
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Tidskriftsartikel (refereegranskat)abstract
- Using the REX-ISOLDE facility at CERN the Coulomb excitation cross sections for the 0(gs)(+)-> 2(1)(+) transition in the beta-unstable isotopes Cd-100,Cd-102,Cd-104 have been measured for the first time. Two different targets were used, which allows for the first extraction of the static electric quadrupole moments Q(2(1)(+)) in Cd-102,Cd-104. In addition to the B(E2) values in Cd-102,Cd-104, a first experimental limit for the B(E2) value in Cd-100 is presented. The data was analyzed using the maximum likelihood method. The provided probability distributions impose a test for theoretical predictions of the static and dynamic moments. The data are interpreted within the shell-model using realistic matrix elements obtained from a G-matrix renormalized CD-Bonn interaction. In view of recent results for the light Sn isotopes the data are discussed in the context of a renormalization of the neutron effective charge. This study is the first to use the reorientation effect for post-accelerated short-lived radioactive isotopes to simultaneously determine the B(E2) and the Q(2(1)(+)) values.
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| 9. |
- Generalov, A., et al.
(författare)
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Strong spin-orbit coupling in the noncentrosymmetric Kondo lattice
- 2018
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Ingår i: Physical Review B. - 2469-9950. ; 98:11
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Tidskriftsartikel (refereegranskat)abstract
- Strong spin-orbit coupling (SOC) in combination with a lack of inversion symmetry and exchange magnetic interaction proves to be a sophisticated instrument allowing efficient control of the spin orientation, energy and trajectories of two-dimensional (2D) electrons and holes trapped at surfaces or interfaces. Exploiting Kondo-related phenomena and crystal-electric-field effects at reduced dimensionalities opens new opportunities to handle their spin-dependent properties offering novel functionalities. We consider here a 2D Kondo lattice represented by a Si-Ir-Si-Yb (SISY) surface block of the heavy-fermion material YbIr2Si2. We show that the Kondo interaction with 4f moments allows finely tuning the group velocities of the strongly spin-polarized carriers in 2D itinerant states of this noncentrosymmetric system. To unveil the peculiarities of this interaction, we used angle-resolved photoemission measurements complemented by first-principles calculations. We established that the strong SOC of the Ir atoms induces spin polarization of the 2D states in SISY block, while the 2D lattice of Yb 4f moments acts as a source for coherent f-d interplay. The strong SOC and lack of inversion symmetry turn out to lead not only to the anticipated Rashba-like splitting of the 2D states, but also to spin splitting of the 4f Kramers doublets. They couple temperature-dependently to the spin-polarized 2D states and thereby guide the properties of the latter.
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| 10. |
- Nara Singh, B. S., et al.
(författare)
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Exotic Nuclear Studies Around and Below A=100
- 2011
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Ingår i: 4th International Conference on Proton Emitting Nuclei and Related Topics, PROCON2011. - : AIP. - 9780735409835 ; 1409, s. 19-24
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Konferensbidrag (refereegranskat)abstract
- A RISING experiment with an aim to study exotic Cd nuclei was carried out at GSI-FRS facility. Some preliminary results from this experiment are presented here. In particular, the β decay of 96Cd to 96Ag revealed the existence of a high spin isomer predicted a few decades ago. In this context, the structures of both these nuclei are discussed. Shell model calculations using the Gross-Frenkel interaction are used to interpret the results.
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