SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Gaffney L.P.) "

Sökning: WFRF:(Gaffney L.P.)

  • Resultat 1-29 av 29
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Andel, B., et al. (författare)
  • β -delayed fission of isomers in Bi 188
  • 2020
  • Ingår i: Physical Review C. - 2469-9985. ; 102:1
  • 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.
  •  
2.
  • Barzakh, A., et al. (författare)
  • Large Shape Staggering in Neutron-Deficient Bi Isotopes
  • 2021
  • Ingår i: Physical Review Letters. - 0031-9007. ; 127:19
  • Tidskriftsartikel (refereegranskat)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.
  •  
3.
  • Bennett, S. A., et al. (författare)
  • Direct Determination of Fission-Barrier Heights Using Light-Ion Transfer in Inverse Kinematics
  • 2023
  • Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 130:20, s. 202501-
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate a new technique for obtaining fission data for nuclei away from β stability. These types of data are pertinent to the astrophysical r process, crucial to a complete understanding of the origin of the heavy elements, and for developing a predictive model of fission. These data are also important considerations for terrestrial applications related to power generation and safeguarding. Experimentally, such data are scarce due to the difficulties in producing the actinide targets of interest. The solenoidal-spectrometer technique, commonly used to study nucleon-transfer reactions in inverse kinematics, has been applied to the case of transfer-induced fission as a means to deduce the fission-barrier height, among other variables. The fission-barrier height of ^{239}U has been determined via the ^{238}U(d,pf) reaction in inverse kinematics, the results of which are consistent with existing neutron-induced fission data indicating the validity of the technique.
  •  
4.
  • Bree, N, et al. (författare)
  • Shape Coexistence in the Neutron-Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation.
  • 2014
  • Ingår i: Physical Review Letters. - 1079-7114. ; 112:16
  • 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.
  •  
5.
  •  
6.
  • Butler, P. A., et al. (författare)
  • Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive ^{222}Ra and ^{228}Ra Beams
  • 2020
  • Ingår i: Physical Review Letters. - 1079-7114. ; 124:4
  • Tidskriftsartikel (refereegranskat)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.
  •  
7.
  • Butler, P. A., et al. (författare)
  • The observation of vibrating pear-shapes in radon nuclei
  • 2019
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
  • Tidskriftsartikel (refereegranskat)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.
  •  
8.
  • Čolović, P., et al. (författare)
  • Population of lead isotopes in binary reactions using a Rb 94 radioactive beam
  • 2020
  • Ingår i: Physical Review C. - 2469-9985. ; 102:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We measured absolute cross sections for neutron transfer channels populated in the Rb94+Pb208 binary reaction. Cross sections have been extracted identifying directly the lead isotopes with the high efficiency MINIBALL γ-ray array coupled to a particle detector combined with a radioactive Rb94 beam delivered at Elab=6.2 MeV/nucleon by the HIE-ISOLDE facility. We observed sizable cross sections in the neutron-rich mass region, where the heavy partner acquires neutrons. A fair agreement between the measured cross sections with those from GRAZING calculations gives confidence in the cross-section predictions of more neutron-rich nuclei produced via a larger number of transferred nucleons.
  •  
9.
  • Gaffney, L. P., et al. (författare)
  • Collectivity in the light radon nuclei measured directly via Coulomb excitation
  • 2015
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:6
  • 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.
  •  
10.
  • Gaffney, L. P., et al. (författare)
  • Low-energy Coulomb excitation of 62Fe and 62Mn following in-beam decay of 62Mn
  • 2015
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:10, s. 1-9
  • 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.
  •  
11.
  • Gaffney, L. P., et al. (författare)
  • Studies of pear-shaped nuclei using accelerated radioactive beams
  • 2013
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 497:7448, s. 199-204
  • Tidskriftsartikel (refereegranskat)abstract
    • There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are 'octupole deformed', that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments were performed using accelerated beams of heavy, radioactive ions. Our data on Rn-220 and Ra-224 show clear evidence for stronger octupole deformation in the latter. The results enable discrimination between differing theoretical approaches to octupole correlations, and help to constrain suitable candidates for experimental studies of atomic electric-dipole moments that might reveal extensions to the standard model.
  •  
12.
  • Illana, A., et al. (författare)
  • Coulomb excitation of 74,76Zn
  • 2023
  • Ingår i: Physical Review C. - 2469-9985. ; 108:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The first experiment using radioactive beams post-accelerated by the HIE-ISOLDE facility has enabled to obtain a precise set of B(E2) transition probabilities in neutron-rich 74,76Zn isotopes. The resulting B(E2; 2+1→0+1) values are consistent with those determined in earlier REX-ISOLDE measurements. While the B(E2; 4+1→2+1) transition probability in 76Zn is also in agreement with earlier Coulomb-excitation results, the value obtained for 74Zn is considerably lower. For the first time, a spectroscopic quadrupole moment of the 2+1 state was measured for an exotic nucleus in this mass region. A detailed comparison is presented with large-scale shell-model and Monte Carlo shell-model calculations.
  •  
13.
  • Johansen, J. G., et al. (författare)
  • Experimental study of bound states in Be-12 through low-energy Be-11(d,p)-transfer reactions
  • 2013
  • Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 88:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The bound states of Be-12 have been studied through a Be-11(d, p) Be-12 transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of Be-11 was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in Be-12. The gamma-ray detection enabled a clear identification of the four known bound states in Be-12, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from distorted wave Born approximation (DWBA) calculations and have been compared to previous experimental and theoretical results.
  •  
14.
  • Johansen, Jacob G., et al. (författare)
  • Study of bound states in 10Be by one neutron removal reactions of 11Be
  • 2017
  • Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 44:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The bound states of 10Be have been studied by removing single neutrons from 11Be nuclei. A 2.8 MeV u-1 beam of 11Be was produced at ISOLDE, CERN and directed on to both proton and deuteron targets inducing one-neutron removal reactions. Charged particles were detected to identify the two reaction channels (d, t) and (p, d), and the individual states in 10Be were identified by gamma detection. All bound states but one were populated and identified in the (d, t) reaction. The combination of REX-ISOLDE and MINIBALL allowed for a clean separation of the high-lying states in 10Be. This is the first time these states have been separated in a reaction experiment. Differential cross sections have been calculated for all the reaction channels and compared to DWBA calculations. Spectroscopic factors are derived and compared to values from the litterature. While the overall agreement between the spectrocopic factors is poor, the ratio between the ground state and the first excited state is in agreement with the previous measured ones. Furthermore, a significant population of the state is observed, which which may indicate the presence of multi-step processes at our beam energy.
  •  
15.
  • Kern, R., et al. (författare)
  • Restoring the valence-shell stabilization in Nd 140
  • 2020
  • Ingår i: Physical Review C. - 2469-9985. ; 102:4
  • Tidskriftsartikel (refereegranskat)abstract
    • A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of Nd140 using the multistep Coulomb-excitation code gosia. The absolute M1 strengths, B(M1;22+→21+)=0.033(8)μN2,B(M1;23+→21+)=0.26-0.10+0.11μN2, and B(M1;24+→21+)<0.04μN2, identify the 23+ state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of Nd140. The degree of F-spin mixing in Nd140 was quantified with the determination of the mixing matrix element VF-mix<7-7+13keV.
  •  
16.
  • Kesteloot, N., et al. (författare)
  • Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes
  • 2015
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po-196,Po-198,Po-200,Po-202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po-196,Po-198, the transitional and diagonal matrix elements of the 2(1)(+) state are determined. In Po-196,Po-198 multistep Coulomb excitation is observed, populating the 4(1)(+), 0(2)(+), and 2(2)(+) states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from Po-196 onwards. Three model descriptions are used to compare to the data. Calculations with the beyond-mean-field model, the interacting boson model, and the general Bohr Hamiltonian model show partial agreement with the experimental data. Finally, calculations with a phenomenological two-level mixing model hint at the mixing of a spherical structure with a weakly deformed rotational structure.
  •  
17.
  • Korten, W., et al. (författare)
  • Physics opportunities with the Advanced Gamma Tracking Array : AGATA
  • 2020
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 56:5
  • Forskningsöversikt (refereegranskat)abstract
    • New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4 pi instrument. AGATA is a high-resolution gamma -ray spectrometer, solely built from highly segmented high-purity Ge detectors, capable of measuring gamma rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual gamma -ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.
  •  
18.
  • Martel, I., et al. (författare)
  • An innovative Superconducting Recoil Separator for HIE-ISOLDE
  • 2023
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : ELSEVIER. - 0168-583X .- 1872-9584. ; 541, s. 176-179
  • Tidskriftsartikel (refereegranskat)abstract
    • The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the “Isolde Superconducting Recoil Separator” (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.
  •  
19.
  • Morrison, L., et al. (författare)
  • Dealing with contaminants in Coulomb excitation of radioactive beams
  • 2020
  • Ingår i: 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK. - : IOP Publishing. - 1742-6588. ; 1643
  • Konferensbidrag (refereegranskat)abstract
    • Data analysis of the Coulomb excitation experiment of the exotic 206Hg nucleus, recently performed at CERN's HIE-ISOLDE facility, needs to account for the contribution to target excitation due to the strongly-present beam contaminant 130Xe. In this paper, the contamination subtraction procedure is presented.
  •  
20.
  • Morrison, L., et al. (författare)
  • Quadrupole and octupole collectivity in the semi-magic nucleus 20680Hg126
  • 2023
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 838
  • Tidskriftsartikel (refereegranskat)abstract
    • The first low-energy Coulomb-excitation measurement of the radioactive, semi-magic, two proton-hole nucleus 206Hg, was performed at CERN's recently-commissioned HIE-ISOLDE facility. Two γ rays depopulating low-lying states in 206Hg were observed. From the data, a reduced transition strength B(E2; 2+1 → 0+1) = 4.4(6) W.u. was determined, the first such value for an N=126 nucleus south of 208Pb, which is found to be slightly lower than that predicted by shell-model calculations. In addition, a collective octupole state was identified at an excitation energy of 2705 keV, for which a reduced B(E3) transition probability of 30+10-30 W.u. was extracted. These results are crucial for understanding both quadrupole and octupole collectivity in the vicinity of the heaviest doubly-magic nucleus 208Pb, and for benchmarking a number of theoretical approaches in this key region. This is of particular importance given the paucity of data on transition strengths in this region, which could be used, in principle, to test calculations relevant to the astrophysical r-process.
  •  
21.
  • Morrison, L., et al. (författare)
  • Quadrupole deformation of Xe 130 measured in a Coulomb-excitation experiment
  • 2020
  • Ingår i: Physical Review C. - 2469-9985. ; 102:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-lying states in the isotope Xe130 were populated in a Coulomb-excitation experiment performed at CERN's HIE-ISOLDE facility. The magnitudes and relative signs of seven E2 matrix elements and one M1 matrix element coupling five low-lying states in Xe130 were determined using the semiclassical coupled-channel Coulomb-excitation least-squares search code gosia. The diagonal E2 matrix elements of both the 21+ and 41+ states were extracted for the first time. The reduced transition strengths are in line with those obtained from previous measurements. Experimental results were compared with the general Bohr Hamiltonian with the microscopic input from mean-field theory utilizing universal nuclear energy density functional (UNEDF0), shell-model calculations using the GCN50:82 and SN100PN interactions, and simple phenomenological models (Davydov-Filippov and γ-soft). The extracted shape parameters indicate triaxial-prolate deformation in the ground-state band. In general, good agreement between theoretical predictions and experimental values was found, while neither phenomenological model was found to provide an adequate description of Xe130.
  •  
22.
  • Parr, E., et al. (författare)
  • Single-particle states and parity doublets in odd- Z Ac 221 and Pa 225 from α -decay spectroscopy
  • 2022
  • Ingår i: Physical Review C. - 2469-9985. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-lying states in the odd-Z isotopes Ac13289221 and Pa13491225 have been studied using α-particle and αγ-coincidence spectroscopy in the Pa225→Ac221→Fr217 decay chain. Ground-state spin and parity assignments of Iπ = 5/2- are proposed for both Ac221 and Pa225, with the odd proton occupying the ω = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In Ac221, excited states in the bands based on the ω = 5/2 and ω = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-A members of the isotope chains down to N = 132 for Ac and N = 134 for Pa, before reaching the transitional region at N = 130.
  •  
23.
  • Rosiak, D., et al. (författare)
  • Enhanced Quadrupole and Octupole Strength in Doubly Magic Sn 132
  • 2018
  • Ingår i: Physical Review Letters. - 0031-9007. ; 121:25
  • Tidskriftsartikel (refereegranskat)abstract
    • The first 2+ and 3- states of the doubly magic nucleus Sn132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb206 target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0g.s.+→21+, 0g.s.+→31-, and 21+→31- in Sn132. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2;0g.s.+→21+) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of Sn132.
  •  
24.
  • Scheck, M., et al. (författare)
  • Do nuclei go pear-shaped? Coulomb excitation of Rn-220 and Ra-224 at REX-ISOLDE (CERN)
  • 2015
  • Ingår i: Cgs15 - Capture Gamma-ray Spectroscopy and Related Topics. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 93, s. 01038-01038
  • Konferensbidrag (refereegranskat)abstract
    • The IS475 collaboration conducted Coulomb-excitation experiments with post-accelerated radioactive Rn-220 and Ra-224 beams at the REX-ISOLDE facility. The beam particles (E-beam: 2.83 MeV/u) were Coulomb excited using Ni-60, Cd-14, and Sn-120 scattering targets. De-excitation gamma-rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured gamma-ray yields. The extracted < 3 parallel to E3 parallel to 0(+)> matrix element allows for the conclusion that, while Rn-220 represents an octupole vibrational system, Ra-224 has already substantial octupole correlations in its ground state. This finding has i(m)plications for the search of CP-violating Schiff moments in the atomic systems of the adjacent odd-mass nuclei.
  •  
25.
  • Seidlitz, M., et al. (författare)
  • Coulomb excitation of Na-29,Na-30: Mapping the borders of the island of inversion
  • 2014
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Nuclear shell evolution in neutron-rich Na nuclei around N = 20 was studied by determining reduced transition probabilities, i.e., B(E2) and B(M1) values, in order to map the border of the island of inversion. To this end Coulomb-excitation experiments, employing radioactive Na-29,Na-30 beams with a final beam energy of 2.85 MeV/nucleon, were performed at REX-ISOLDE, CERN. De-excitation gamma rays were detected by the MINIBALL gamma-ray spectrometer in coincidence with scattered particles in a segmented Si detector. Transition probabilities to excited states were deduced. The measured B(E2) values agree well with shell-model predictions, supporting the idea that in the Na isotopic chain the ground-state wave function contains significant intruder admixture already at N = 18, with N = 19 having an almost pure two-particle-two-hole deformed ground-state configuration.
  •  
26.
  • Spagnoletti, P., et al. (författare)
  • Coulomb excitation of Rn 222
  • 2022
  • Ingår i: Physical Review C. - 2469-9985. ; 105:2
  • Tidskriftsartikel (refereegranskat)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.
  •  
27.
  • Stryjczyk, M., et al. (författare)
  • Decay studies of the long-lived states in Tl 186
  • 2020
  • Ingår i: Physical Review C. - 2469-9985. ; 102:2
  • Tidskriftsartikel (refereegranskat)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.
  •  
28.
  • Warr, N., et al. (författare)
  • The Miniball spectrometer
  • 2013
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 49:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The Miniball germanium detector array has been operational at the REX (Radioactive ion beam EXperiment) post accelerator at the Isotope Separator On-Line facility ISOLDE at CERN since 2001. During the last decade, a series of successful Coulomb excitation and transfer reaction studies have been performed with this array, utilizing the unique and high-quality radioactive ion beams which are available at ISOLDE. In this article, an overview is given of the technical details of the full Miniball setup, including a description of the.-ray and particle detectors, beam monitoring devices and methods to deal with beam contamination. The specific timing properties of the REX-ISOLDE facility are highlighted to indicate the sensitivity that can be achieved with the full Miniball setup. The article is finalized with a summary of some physics highlights at REX-ISOLDE and the utilization of the Miniball germanium detectors at other facilities.
  •  
29.
  • Wrzosek-Lipska, K., et al. (författare)
  • Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes : Coulomb excitation of 182Hg, 184Hg, 186Hg and 188Hg
  • 2019
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 55:8
  • 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.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-29 av 29

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy