| 1. |
- Akkoyun, S., et al.
(author)
-
AGATA - Advanced GAmma Tracking Array
- 2012
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087 .- 1872-9576. ; 668, s. 26-58
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Journal article (peer-reviewed)abstract
- The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector- response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. © 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Reifarth, R., et al.
(author)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
-
In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
-
Conference paper (peer-reviewed)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 3. |
- Hadynska-Klek, K., et al.
(author)
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Quadrupole collectivity in Ca-42 from low-energy Coulomb excitation with AGATA
- 2018
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In: Physical Review C. - : AMER PHYSICAL SOC. - 2469-9985 .- 2469-9993. ; 97:2
-
Journal article (peer-reviewed)abstract
- ACoulomb-excitation experiment to study electromagnetic properties of Ca-42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. gamma rays from excited states in Ca-42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca-42, including the diagonal E2 matrix elements of 2(1)(+) and 2(2)(+) states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 0(1),(+)(2) and 2(1,2)(+) states, as well as triaxiality for 0(1,2)(+) states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca-42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca-42.
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| 4. |
- Hadynska-Klek, K., et al.
(author)
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Superdeformed and Triaxial States in Ca-42
- 2016
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 117:6
-
Journal article (peer-reviewed)abstract
- Shape parameters of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca-42 were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. Experimental evidence for superdeformation of the band built on 0(2)(+) has been obtained and the role of triaxiality in the A similar to 40 mass region is discussed. Furthermore, the potential of Coulomb excitation as a tool to study superdeformation has been demonstrated for the first time.
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| 5. |
- Hadynska-Klek, K., et al.
(author)
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Towards The Determination Of Superdeformation In Ca-42
- 2013
-
In: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 44:3, s. 617-625
-
Journal article (peer-reviewed)abstract
- The Coulomb excitation experiment to study electromagnetic structure of low-lying states in Ca-42 with a focus on a possible superdeformation in this nucleus was performed at the Laboratori Nazionali di Legnaro in Italy. Preliminary values of the determined quadrupole deformation parameters for both the ground state band and the presumed superdeformed band are presented.
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| 6. |
- Jentschel, M., et al.
(author)
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EXILL - a high-efficiency, high-resolution setup for gamma-spectroscopy at an intense cold neutron beam facility
- 2017
-
In: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 12
-
Journal article (peer-reviewed)abstract
- In the EXILL campaign a highly efficient array of high purity germanium (HPGe) detectors was operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of gamma-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10(8) ns(-1)cm(2) at the target position and negligible neutron halo. The targetwas surrounded by an array of eight to ten anti-Compton shielded EXOGAMClover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr3:(Ce) detectors from the FATIMA collaboration. The detectorswere arranged in an array of rhombicuboctahedron geometry, providing the possibility to carry out very precise angular correlation and directional-polarization correlation measurements. The triggerless acquisition system allowed a signal collection rate of up to 6 x 10(5) Hz. The data allowed to set multi-fold coincidences to obtain decay schemes and in combination with the FATIMA array of LaBr3:(Ce) detectors to analyze half-lives of excited levels in the pico-to microsecond range. Precise energy and efficiency calibrations of EXILL were performed using standard calibration sources of Ba-133, Co-60 and Eu-152 as well as data from the reactions Al-27(n, gamma)Al-28 and Cl-35(n,gamma)Cl-36 in the energy range from 30 keV up to 10MeV.
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| 7. |
- Mason, P, et al.
(author)
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Octupole signatures in Ba-124,Ba-125
- 2005
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In: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1729-S1733
-
Journal article (peer-reviewed)abstract
- The gamma decay of the nuclei Ba-121,Ba-125 has been investigated with the EUROBALL array, using the reaction Ni-64+Ni-64 at E-beam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus Ba-125, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J(pi) = 3(-) level of the nucleus Ba-124 has been identified for the first time. Its excitation energy is in very good agreement with a prediction based on a microscopic model including octupole interactions.
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| 8. |
- Modamio, V., et al.
(author)
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Lifetime measurements in neutron-rich Co-63,Co-65 isotopes using the AGATA demonstrator
- 2013
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In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:4, s. 044326-
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Journal article (peer-reviewed)abstract
- Lifetimes of the low-lying (11/2(-)) states in Co-63,Co-65 have been measured employing the recoil distance doppler shift method (RDDS) with the AGATA gamma-ray array and the PRISMA mass spectrometer. These nuclei were populated via a multinucleon transfer reaction by bombarding a U-238 target with a beam of Ni-64. The experimental B(E2) reduced transition probabilities for Co-63,Co-65 are well reproduced by large-scale shell-model calculations that predict a constant trend of the B(E2) values up to the N = 40 Co-67 isotope.
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| 9. |
- Ciemala, M., et al.
(author)
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Testing ab initio nuclear structure in neutron-rich nuclei : Lifetime measurements of second 2(+) state in C-16 and O-20
- 2020
-
In: Physical Review C. - : AMER PHYSICAL SOC. - 2469-9985 .- 2469-9993. ; 101:2
-
Journal article (peer-reviewed)abstract
- To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2(+) state in neutron-rich O-20, tau(2(2)(+)) = 150(-30)(+80) fs, and an estimate for the lifetime of the second 2(+) state in C-16 have been obtained for the first time. The results were achieved via a novel Monte Carlo technique that allowed us to measure nuclear state lifetimes in the tens-to-hundreds of femtoseconds range by analyzing the Doppler-shifted gamma-transition line shapes of products of low-energy transfer and deep-inelastic processes in the reaction O-18 (7.0 MeV/u) + Ta-181. The requested sensitivity could only be reached owing to the excellent performances of the Advanced gamma-Tracking Array AGATA, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The experimental lifetimes agree with predictions of ab initio calculations using two- and three-nucleon interactions, obtained with the valence-space in-medium similarity renormalization group for O-20 and with the no-core shell model for C-16. The present measurement shows the power of electromagnetic observables, determined with high-precision gamma spectroscopy, to assess the quality of first-principles nuclear structure calculations, complementing common benchmarks based on nuclear energies. The proposed experimental approach will be essential for short lifetime measurements in unexplored regions of the nuclear chart, including r-process nuclei, when intense beams, produced by Isotope Separation On-Line (ISOL) techniques, become available.
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| 10. |
- Goldkuhle, A., et al.
(author)
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Lifetime measurements in Ti-52,Ti-54 to study shell evolution toward N=32
- 2019
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 100:5
-
Journal article (peer-reviewed)abstract
- Lifetimes of the excited states in the neutron-rich Ti-52,Ti-54 nuclei, produced in a multinucleon-transfer reaction, were measured by employing the Cologne plunger device and the recoil-distance Doppler-shift method. The experiment was performed at the Grand Accelerateur National d'Ions Lourds facility by using the Advanced Gamma Tracking Array for the gamma-ray detection, coupled to the large-acceptance variable mode spectrometer for an event-by-event particle identification. A comparison between the transition probabilities obtained from the measured lifetimes of the 2(1)(+) to 8(1)(+) yrast states in Ti-52,Ti-54 and that from the shell-model calculations based on the well-established GXPF1A, GXPF1B, and KB3G fp shell interactions support the N = 32 subshell closure. The B(E2) values for Ti-52 determined in this work are in disagreement with the known data, but are consistent with the predictions of the shell-model calculations and reduce the previously observed pronounced staggering across the even-even titanium isotopes.
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| 11. |
- Louchart, C., et al.
(author)
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Collective nature of low-lying excitations in Zn-70,Zn-72,Zn-74 from lifetime measurements using the AGATA spectrometer demonstrator
- 2013
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:5
-
Journal article (peer-reviewed)abstract
- Background: Neutron-rich nuclei with protons in the fp shell show an onset of collectivity around N=40. Spectroscopic information is required to understand the underlying mechanism and to determine the relevant terms of the nucleon-nucleon interaction that are responsible for the evolution of the shell structure in this mass region. Methods: We report on the lifetime measurement of the first 2(+) and 4(+) states in Zn-70,Zn-72 ,Zn-74 and the first 6(+) state in Zn-72 using the recoil distance Doppler shift method. The experiment was carried out at the INFN Laboratory of Legnaro with the AGATA demonstrator, first phase of the Advanced Gamma Tracking Array of highly segmented, high-purity germanium detectors coupled to the PRISMA magnetic spectrometer. The excited states of the nuclei of interest were populated in the deep inelastic scattering of a Ge-76 beam impinging on a U-238 target. Results: The maximum of collectivity along the chain of Zn isotopes is observed for Zn-72 at N=42. An unexpectedly long lifetime of 20(-5.2)(+1.8) ps was measured for the 4(+) state in Zn-74. Conclusions: Our results lead to small values of the B(E2;4(1)(+) -> 21(+))/B(E2;2(1)(+->)0(1)(+)) ratio for Zn-72,Zn-74, suggesting a significant noncollective contribution to these excitations. These experimental results are not reproduced by state-of-the-art microscopic models and call for lifetime measurements beyond the first 2(+) state in heavy zinc and nickel isotopes.
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| 12. |
- Wuttke, Matthias, et al.
(author)
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A catalog of genetic loci associated with kidney function from analyses of a million individuals
- 2019
-
In: Nature Genetics. - : NATURE PUBLISHING GROUP. - 1061-4036 .- 1546-1718. ; 51:6, s. 957-972
-
Journal article (peer-reviewed)abstract
- Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through transancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these,147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.
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| 13. |
- Avigo, R., et al.
(author)
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Low-lying electric dipole gamma-continuum for the unstable Fe-62,64 nuclei : Strength evolution with neutron number
- 2020
-
In: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 811
-
Journal article (peer-reviewed)abstract
- The gamma-ray emission from the nuclei Fe-62,Fe-64 following Coulomb excitation at bombarding energy of 400-440 AMeV was measured with special focus on E1 transitions in the energy region 4-8 MeV. The unstable neutron-rich nuclei Fe-62,Fe-64 were produced at the FAIR-GSI laboratories and selected with the FRS spectrometer. The gamma decay was detected with AGATA. From the measured gamma-ray spectra the summed E1 strength is extracted and compared to microscopic quasi-particle phonon model calculations. The trend of the E1 strength with increasing neutron number is found to be fairly well reproduced with calculations that assume a rather complex structure of the 1(-) states (three-phonon states) inducing a strong fragmentation of the E1 nuclear response below the neutron binding energy.
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| 14. |
- Biswas, S., et al.
(author)
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Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich(51)( 122-)(131)Sb isotopes
- 2019
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 99:6
-
Journal article (peer-reviewed)abstract
- Background: Levels fulfilling the seniority scheme and relevant isomers are commonly observed features in semimagic nuclei; for example, in Sn isotopes (Z = 50). Seniority isomers in Sn, with dominantly pure neutron configurations, directly probe the underlying neutron-neutron (vv) interaction. Furthermore, an addition of a valence proton particle or hole, through neutron-proton (v pi) interaction, affects the neutron seniority as well as the angular momentum. Purpose: Benchmark the reproducibility of the experimental observables, like the excitation energies (E-x) and the reduced electric-quadrupole transition probabilities [B(E2)], with the results obtained from shell-model interactions for neutron-rich Sn and Sb isotopes with N < 82. Study the sensitivity of the aforementioned experimental observables to the model interaction components. Furthermore, explore from a microscopic point of view the structural similarity between the isomers in Sn and Sb, and thus the importance of the valence proton. Methods: The neutron-rich Sb122-131 isotopes were produced as fission fragments in the reaction Be-9(U-238, f) with 6.2 MeV/u beam energy. A unique setup, consisting of AGATA, VAMOS++, and EXOGAM detectors, was used which enabled the prompt-delayed gamma-ray spectroscopy of fission fragments in the time range of 100 ns to 200 mu s. Results: New isomers and prompt and delayed transitions were established in the even-A Sb122-131 isotopes. In the odd-A Sb122-131 isotopes, new prompt and delayed gamma-ray transitions were identified, in addition to the confirmation of the previously known isomers. The half-lives of the isomeric states and the B(E2) transition probabilities of the observed transitions depopulating these isomers were extracted. Conclusions: The experimental data was compared with the theoretical results obtained in the framework of large-scale shell-model (LSSM) calculations in a restricted model space. Modifications of several components of the shell-model interaction were introduced to obtain a consistent agreement with the excitation energies and the B(E2) transition probabilities in neutron-rich Sn and Sb isotopes. The isomeric configurations in Sn and Sb were found to be relatively pure. Furthermore, the calculations revealed that the presence of a single valence proton, mainly in the g(7/2) orbital in Sb isotopes, leads to significant mixing (due to the v pi interaction) of (i) the neutron seniorities (upsilon(v)) and (ii) the neutron angular momentum (I-v). The above features have a weak impact on the excitation energies, but have an important impact on the B(E2) transition probabilities. In addition, a constancy of the relative excitation energies irrespective of neutron seniority and neutron number in Sn and Sb was observed.
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| 15. |
- Boso, A., et al.
(author)
-
Isospin dependence of electromagnetic transition strengths among an isobaric triplet
- 2019
-
In: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 797
-
Journal article (peer-reviewed)abstract
- Electric quadrupole matrix elements, M-p, for the J(pi) = 2(+) -> 0(+), Delta T = 0, T = 1 transitions across the A = 46 isobaric multiplet Cr-46-V-46-Ti-46 have been measured at GSI with the FRS-LYCCA-AGATA setup. This allows direct insight into the isospin purity of the states of interest by testing the linearity of M-p with respect to T-z. Pairs of nuclei in the T = 1 triplet were studied using identical reaction mechanisms in order to control systematic errors. The M-p values were obtained with two different methodologies: (i) a relativistic Coulomb excitation experiment was performed for Cr-46 and Ti-46; (ii) a "stretched target" technique was adopted here, for the first time, for lifetime measurements in V-46 and Ti-46. A constant value of M-p across the triplet has been observed. Shell-model calculations performed within the fp shell fail to reproduce this unexpected trend, pointing towards the need of a wider valence space. This result is confirmed by the good agreement with experimental data achieved with an interaction which allows excitations from the underlying sd shell. A test of the linearity rule for all published data on complete T = 1 isospin triplets is presented. (C) 2019 The Author(s). Published by Elsevier B.V.
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| 16. |
- Cederwall, B., et al.
(author)
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Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru-88
- 2020
-
In: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 124:6
-
Journal article (peer-reviewed)abstract
- The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide Ru-88(44)44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in Ru-88 were populated via the Fe-54(Ar-36, 2n gamma)Ru-88* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. The observed gamma-ray cascade is assigned to Ru-88 using clean prompt gamma-gamma-2-neutron coincidences in anticoincidence with the detection of charged particles, confirming and extending the previously assigned sequence of low-lying excited states. It is consistent with a moderately deformed rotating system exhibiting a band crossing at a rotational frequency that is significantly higher than standard theoretical predictions with isovector pairing, as well as observations in neighboring N > Z nuclides. The direct observation of such a "delayed" rotational alignment in a deformed N = Z nucleus is in agreement with theoretical predictions related to the presence of strong isoscalar neutron-proton pair correlations.
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| 17. |
- Clement, E., et al.
(author)
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Conceptual design of the AGATA 1 π array at GANIL
- 2017
-
In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 855, s. 1-12
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Journal article (peer-reviewed)abstract
- The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This setup exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam γ-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy γ rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on simulations, expected performances of the AGATA l π array are presented.
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| 18. |
- Delafosse, C., et al.
(author)
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Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region : A Hint from Lifetime Measurements
- 2018
-
In: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:19
-
Journal article (peer-reviewed)abstract
- Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution.
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| 19. |
- Fernández, A., et al.
(author)
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Reinterpretation of excited states in 212Po: Shell-model multiplets rather than α-cluster states
- 2021
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 104:5
-
Journal article (peer-reviewed)abstract
- A γ-ray spectroscopic study of 212Po was performed at the Grand Accélérateur National d'Ions Lourds, using the inverse kinematics α-transfer reaction 12C(208Pb,212Po)8Be and the AGATA spectrometer. A careful analysis based on γγ coincidence relations allowed us to establish 14 new excited states in the energy range between 1.9 and 3.3 MeV. None of these states, however, can be considered as candidates for the levels with spins and parities of 1− and 2− and excitation energies below 2.1 MeV, which have been predicted by recent α-cluster model calculations. A systematic comparison of the experimentally established excitation scheme of 212Po with shell-model calculations was performed. This comparison suggests that the six states with excitation energies (spins and parities) of 1744 (4−), 1751 (8−), 1787 (6−), 1946 (4−), 1986 (8−), and 2016 (6−) keV, which previously were interpreted as α-cluster states, may in fact be of positive parity and belong to low-lying shell-model multiplets. This reinterpretation of the structure of 212Po is supported by experimental information with respect to the linear polarization of γ rays, which suggests a magnetic character of the 432-keV γ ray decaying from the state at an excitation energy of 1787 keV to the 6+ yrast state, and exclusive reaction cross sections.
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| 20. |
- Girard-Alcindor, V., et al.
(author)
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New narrow resonances observed in the unbound nucleus F 15
- 2022
-
In: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 105:5
-
Journal article (peer-reviewed)abstract
- The structure of the unbound F15 nucleus is investigated using the inverse kinematics resonant scattering of a radioactive O14 beam impinging on a CH2 target. The analysis of H1(O14,p)O14 and H1(O14,2p)N13 reactions allowed the confirmation of the previously observed narrow 1/2- resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2- and 3/2- resonances. The newly observed levels decay by 1p emission to the ground of O14, and by sequential 2p emission to the ground state of N13 via the 1- resonance of O14. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2- and 3/2- resonances may be collectivized by the continuum coupling to nearby 2p- and 1p-decay channels. The observed excitation function H1(O14,p)O14 and resonance spectrum in F15 are well reproduced in the unified framework of the GSM.
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| 21. |
- John, P. R., et al.
(author)
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Shape evolution in the neutron-rich osmium isotopes : Prompt gamma-ray spectroscopy of Os-196
- 2014
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 90:2, s. 021301-
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Journal article (peer-reviewed)abstract
- The shape transition in the neutron-rich Os isotopes is studied by investigating the neutron-rich Os-196 nucleus through in-beam gamma-ray spectroscopy using a two-proton transfer reaction from a Pt-198 target to a Se-82 beam. The beam-like recoils were detected and identified with the large-acceptance magnetic spectrometer PRISMA, and the coincident gamma rays were measured with the advanced gamma tracking array (AGATA) demonstrator. The de-excitation of the low-lying levels of the yrast-band of Os-196 were identified for the first time. The results are compared with state-of-the-art beyond-mean-field calculations, performed for the even-even Os188-198 isotopes. The new results suggest a smooth transition in the Os isotopes from a more axial rotational behavior towards predominately vibrational nuclei through triaxial configurations. An almost perfect gamma-unstable/triaxial rotor yrast band is predicted for Os-196 which is in agreement with the experimentally measured excited states.
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| 22. |
- Korten, W., et al.
(author)
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Physics opportunities with the Advanced Gamma Tracking Array : AGATA
- 2020
-
In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 56:5
-
Research review (peer-reviewed)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.
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| 23. |
- Pellegri, L., et al.
(author)
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Pygmy dipole resonance in Sn-124 populated by inelastic scattering of O-17
- 2014
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 738, s. 519-523
-
Journal article (peer-reviewed)abstract
- The gamma decay from the high-lying states of Sn-124 was measured using the inelastic scattering of O-17 at 340 MeV. The emitted gamma rays were detected with high resolution with the AGATA demonstrator array and the scattered ions were detected in two segmented Delta E-E silicon telescopes. The angular distribution was measured both for the gamma rays and the scattered O-17 ions. An accumulation of E1 strength below the particle threshold was found and compared with previous data obtained with (gamma,gamma') and (alpha,alpha'gamma) reactions. The present results of elastic scattering, and excitation of E2 and E1 states were analysed using the DWBA approach. From this comprehensive description the isoscalar component of the 1-excited states was extracted. The obtained values are based on the comparison of the data with DWBA calculations including a form factor deduced using a microscopic transition density.
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| 24. |
- Perez-Vidal, R. M., et al.
(author)
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Evidence of Partial Seniority Conservation in the pi g9/2 Shell for the N=50 Isotones
- 2022
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 129:11
-
Journal article (peer-reviewed)abstract
- The reduced transition probabilities for the 4+1 -2+1 and 2+1 -0+1 transitions in 92Mo and 94Ru and for the 4+1 -2+1 and 6+1 -4+1 transitions in 90Zr have been determined in this experiment making use of a multinucleon transfer reaction. These results have been interpreted on the basis of realistic shell-model calculations in the f5=2, p3=2, p1=2, and g9=2 proton valence space. Only the combination of extensive lifetime information and large scale shell-model calculations allowed the extent of the seniority conservation in the N = 50 g9=2 orbital to be understood. The conclusion is that seniority is largely conserved in the first 71g9=2 orbital.
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| 25. |
- Polettini, M., et al.
(author)
-
Decay studies in the A∼225 Po-Fr region from the DESPEC campaign at GSI in 2021
- 2022
-
In: Il Nuovo Cimento. - : Società Italiana di Fisica. - 2037-4909. ; 45:5
-
Journal article (peer-reviewed)abstract
- The HISPEC-DESPEC collaboration aims at investigating the structure of exotic nuclei formed in fragmentation reactions with decay spectroscopy measurements, as part of the FAIR Phase-0 campaign at GSI. This paper reports on first results of an experiment performed in spring 2021, with a focus on beta-decaystudies in the Po-Fr nuclei in the 220 < A <230 island of octupole deformation exploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques are being employed, giving an insight into this difficult-to-reach region.
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| 26. |
- Ralet, D., et al.
(author)
-
Evidence of octupole-phonons at high spin in Pb-207
- 2019
-
In: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 797
-
Journal article (peer-reviewed)abstract
- A lifetime measurement of the 19/2(-) state in Pb-207 has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb-208 beam impinging on a Mo-100 enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt gamma rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3, 19/2(-) -> 13/2(+)) = 40(8) W.u. is the first indication of the octupole phonon at high spin in Pb-207. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb-207 is compatible with the contributions from single-phonon and single particle E3 as well as E3 strength arising from the double-octupole-phonon 6(+) state, all adding coherently. A crucial aspect of the coupling model, namely the strong mixing between single-hole and the phonon-hole states, is confirmed in a realistic shell-model calculation. Crown Copyright (C) 2019 Published by Elsevier B.V.
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| 27. |
- Sahin, E., et al.
(author)
-
Shell evolution beyond N=40 : Cu-69,Cu-71,Cu-73
- 2015
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:3
-
Journal article (peer-reviewed)abstract
- The level structure of the neutron-rich Cu-69, Cu-71, and Cu-73 isotopes has been investigated by means of multinucleon transfer reactions. The experiment was performed at Laboratori Nazionali di Legnaro using the AGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states in Cu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrix elements for transitions from excited states in Cu-69,Cu-71,Cu-73 nuclei are used to assess the collective or single-particle character of these states. The results are compared with predictions of large-scale shell-model calculations, giving further insight into the evolution of the proton pf shell as neutrons fill the 1g(9/2) orbital.
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| 28. |
- Yadav, R. B., et al.
(author)
-
Identification of triaxial strongly deformed bands in Hf-168
- 2008
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:4
-
Journal article (peer-reviewed)abstract
- Possible decay pathways associated with three candidates for triaxial strongly deformed (TSD) bands in Hf-168 have been investigated. The spin and excitation energy of the strongest band, TSD1, were determined approximately based on gamma-ray coincidence relationships. Discrete links were established for the second band. The overall agreement between the observed properties of the bands and cranking calculations using the ULTIMATE CRANKER code provides strong support for an interpretation where band TSD1 is associated with a TSD minimum, (epsilon(2),gamma)similar to(0.43,20(degrees)), involving the pi(i(13/2))(2) and the nu(j(15/2)) high-j orbitals. This constitutes the first identification of a TSD band in Hf isotopes, which has been long-predicted by theoretical studies. The second band is understood as being associated with a near-prolate shape and a deformation enhanced with respect to the normal deformed bands. It is proposed to be built on the pi(i(13/2)h(9/2))circle times nu(i(13/2))(2) configuration.
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| 29. |
- Axelsson, A, et al.
(author)
-
Excited superdeformed band in Eu-143
- 1999
-
In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 6:2, s. 175-183
-
Journal article (peer-reviewed)abstract
- A new superdeformed band has been discovered in a EUROBALL experiment and assigned to Eu-143. It has a maximum intensity of 35% of the Eu-143 yrast superdeformed band and the transition energies of the two bands are very similar. Based on comparison with cranked shell model calculations the new band is tentatively assigned the high-N intruder configuration pi 6(2)nu 7(0) and the parity and signature quantum numbers (pi, alpha) = (-1, +1/2). In addition to the already known high-energy transition at 3361 keV another discrete line at 2715 keV was found to be in coincidence with the yrast superdeformed band. However, it was not possible to connect the decay out of either of the superdeformed bands to, known normally deformed states.
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| 30. |
- Axelsson, A, et al.
(author)
-
Excited superdeformed band in Eu-143
- 1999
-
In: EUROPEAN PHYSICAL JOURNAL A. - : SPRINGER VERLAG. - 1434-6001. ; 6:2, s. 175-183
-
Journal article (other academic/artistic)abstract
- A new superdeformed band has been discovered in a EUROBALL experiment and assigned to Eu-143. It has a maximum intensity of 35% of the Eu-143 yrast superdeformed band and the transition energies of the two bands are very similar. Based on comparison with
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| 31. |
- Cederwall, Bo, 1964-, et al.
(author)
-
Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru 88
- 2020
-
In: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 124:6
-
Journal article (peer-reviewed)abstract
- The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide 88Ru has been measured using the combination of the Advanced Gamma Tracking Array (AGATA)spectrometer, the NEDA, and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in 88 Ru were populated via the 54 Feð 36 Ar; 2nγÞ 88 Ru fusion-evaporationreaction at the Grand Accélérateur National d’Ions Lourds (GANIL) accelerator complex. The observed γ-ray cascade is assigned to 88 Ru using clean prompt γ-γ-2-neutron coincidences in anticoincidence with the detection of charged particles, confirming and extending the previously assigned sequence of low-lying excited states. It is consistent with a moderately deformed rotating system exhibiting a band crossing at a rotational frequency that is significantly higher than standard theoretical predictions with isovector pairing, as well as observations in neighboring N > Z nuclides. The direct observation of such a “delayed” rotational alignment in a deformed N 1⁄4 Z nucleus is in agreement with theoretical predictions related to the presence of strong isoscalar neutron-proton pair correlations.
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| 32. |
- Ceruti, S., et al.
(author)
-
Isospin Mixing in Zr-80 : From Finite to Zero Temperature
- 2015
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 115:22
-
Journal article (peer-reviewed)abstract
- The isospin mixing was deduced in the compound nucleus Zr-80 at an excitation energy of E* = 54 MeV from the gamma decay of the giant dipole resonance. The reaction Ca-40 + Ca-40 at E-beam = 136 MeV was used to form the compound nucleus in the isospin I = 0 channel, while the reaction Cl-37 + Ca-44 at E-beam = 95 MeV was used as the reference reaction. The. rays were detected with the AGATA demonstrator array coupled with LaBr3:Ce detectors. The temperature dependence of the isospin mixing was obtained and the zero-temperature value deduced. The isospin-symmetry-breaking correction delta(C) used for the Fermi superallowed transitions was extracted and found to be consistent with beta-decay data.
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| 33. |
- Clement, E., et al.
(author)
-
Spectroscopic quadrupole moments in 124Xe
- 2023
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 107:1
-
Journal article (peer-reviewed)abstract
- Background: The Xe isotopic chain with four valence protons above the Z = 50 shell closure is an ideal laboratory for the study of the evolution of nuclear deformation. At the N = 82 shell closure, 136Xe presents all characteristics of a doubly closed shell nucleus with a spherical shape. In the very neutron-deficient isotopes close to N = 50, the alpha-decay chain of Xe was investigated to probe the radioactive decay properties near the drip-line and the magicity of 100Sn. Additionally, the Xe isotopes present higher order symmetries in the nuclear deformation such as the octupole degree of freedom near N = 60 and N = 90 or O(6) symmetry in stable isotopes.Purpose: The relevance of the O(6) symmetry has been investigated by measuring the spectroscopic quadrupole moment of the first excited states in 124Xe. In the O(6) symmetry limit, the spectroscopic quadrupole moment of collective states is expected to be null.Method: A stable 124Xe beam with energies of 4.03A MeV and 4.11A MeV was used to bombard a natW target at the GANIL facility. Excited states were populated via the safe Coulomb excitation reaction. The collision of the heavy ions with a large Z at low energy make this reaction sensitive to the diagonal E2 matrix element of the excited states. The recoils were detected in the VAMOS++ magnetic spectrometer and the gamma rays in the AGATA tracking array. The least squares fitting code GOSIA was used for the analysis to extract both E2 and M1 transitional and E2 diagonal matrix elements.Results: The rotational ground state band was populated up to the 8+1 state as well as the 2+2 and 4+2 states. Using high precision spectroscopic data to constrain the GOSIA fit, the spectroscopic quadrupole moments of the 2+1 , 4+1 , and 6+1 states were determined for the first time.Conclusions: The spectroscopic quadrupole moments were found to be negative, large, and constant in the ground state band underlining the prolate axially deformed ground state band of 124Xe. The present experimental data confirm that the is broken in 124Xe.
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| 34. |
- Crespi, F. C. L., et al.
(author)
-
1(-) and 2(+) discrete states in Zr-90 populated via the (O-17, O-17 'gamma) reaction
- 2015
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:2
-
Journal article (peer-reviewed)abstract
- 2(+) and 1(-) states in Zr-90 were populated via the (O-17, O-17 'gamma) reaction at 340 MeV. The gamma decay was measured with high resolution using the AGATA (advanced gamma tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2(+), 3(,)(-) and 1(-) states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1(-) state at 6.424 MeV. The comparison of the present (17O, 17O 'gamma) data with existing (gamma,gamma') and (p, p') data in the corresponding region of the gamma continuum (6-11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy.
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| 35. |
- Crespi, F. C. L., et al.
(author)
-
Isospin Character of Low-Lying Pygmy Dipole States in Pb-208 via Inelastic Scattering of O-17 Ions
- 2014
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:1, s. 012501-
-
Journal article (peer-reviewed)abstract
- The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1(-) excited states from 4 to 8 MeV.
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| 36. |
- Klintefjord, M., et al.
(author)
-
Measurement of lifetimes in Fe-62,Fe-64, Co-61,Co-63, and Mn-59
- 2017
-
In: PHYSICAL REVIEW C. - 2469-9985. ; 95:2
-
Journal article (peer-reviewed)abstract
- Lifetimes of the 4(1)(+) states in Fe-62,Fe-64 and the 11/2(1)(-) states in Co-61,Co-63 and Mn-59 were measured at the Grand Accelerateur National d'Ions Lourds (GANIL) facility by using the Advanced Gamma Tracking Array (AGATA) and the large-acceptance variable mode spectrometer (VAMOS++). The states were populated through multinucleon transfer reactions with a U-238 beam impinging on a Ni-64 target, and lifetimes in the picosecond range were measured by using the recoil distance Doppler shift method. The data show an increase of collectivity in the iron isotopes approaching N = 40. The reduction of the subshell gap between the nu 2p(1/2) and nu 1g(9/2) orbitals leads to an increased population of the quasi-SU(3) pair (nu 1g(9/2), nu 2d(5/2)), which causes an increase in quadrupole collectivity. This is not observed for the cobalt isotopes withN < 40 for which the neutron subshell gap is larger due to the repulsive monopole component of the tensor nucleon-nucleon interaction. The extracted experimental B(E2) values are compared with large-scale shell-model calculations and with beyond-mean-field calculations with the Gogny D1S interaction. A good agreement between calculations and experimental values is found, and the results demonstrate in particular the spectroscopic quality of the Lenzi, Nowacki, Poves, and Sieja (LNPS) shell-model interaction.
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| 37. |
- Lieder, R M, et al.
(author)
-
Gamma-ray tracking arrays
- 2001
-
In: PROGRESS IN PARTICLE AND NUCLEAR PHYSICS, VOL 46. ; , s. 399-407
-
Conference paper (peer-reviewed)abstract
- The next generation of 4 pi arrays for high-precision gamma -ray spectroscopy will involve "gamma -ray tracking front-end on digital signal processing techniques, which allows to extract energy, timing and spatial information on the interactions of a gamma -ray in the Ge detector by pulse shape analysis of its signals. Utilizing the information on the positions of the interaction points and the energies released at each point the tracks of the gamma -rays in a Ge shell can be reconstructed in three dimensions.
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| 38. |
- Litzinger, J., et al.
(author)
-
Transition probabilities in neutron-rich Se-80,Se-82 and the role of the nu g(9/2) orbital
- 2018
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 97:4
-
Journal article (peer-reviewed)abstract
- Transition probabilities of intermediate-spin yrast and non-yrast excitations in Se-80,Se-82 were investigated in a recoil distance Doppler-shift (RDDS) experiment performed at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. The Cologne Plunger device for deep inelastic scattering was used for the RDDS technique and was combined with the AGATA Demonstrator array for the gamma-ray detection and coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In Se-80, the level lifetimes of the yrast (6(1)(+)) and (8(1)(+)) states and of a non-yrast band feeding the yrast 4(1)(+) state are determined. A spin and parity assignment of the head of this sideband is discussed based on the experimental results and supported by large-scale shell-model calculations. In Se-82, the level lifetimes of the yrast 6(1)(+) state and the yrare 4(2)(+) state and lifetime limits of the yrast (10(1)(+)) state and of the 5(1)(-) state are determined. Although the experimental results contain large uncertainties, they are interpreted with care in terms of large-scale shell-model calculations using the effective interactions JUN45 and jj44b. The excited states' wave functions are investigated and discussed with respect to the role of the neutron g(9/2) orbital.
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| 39. |
- Litzinger, J., et al.
(author)
-
Transition probabilities in neutron-rich Se-84,Se-86
- 2015
-
In: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 92:6
-
Journal article (peer-reviewed)abstract
- Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se-84,Se-86 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the gamma-ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In Se-86 the level lifetime of the yrast 2(1)(+) state and an upper limit for the lifetime of the 4(1)(+) state are determined for the first time. The results of Se-86 are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in Se-86 are calculated. In semimagic Se-84 level lifetimes of the yrast 4(1)(+) and 6(1)(+) states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B(E2; 2(1)(+) -> 0(1)(+)) and B(E2; 6(1)(+) -> 4(1)(+)) fairly well and point out problems in reproducing the experimental B(E2; 4(1)(+) -> 2(1)(+)).
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| 40. |
- Liu, Xiaoyu, et al.
(author)
-
Evidence for enhanced neutron-proton correlations from the level structure of theN = Z + 1 nucleus 87Tc
-
In: PHYSICAL REVIEW C.
-
Journal article (other academic/artistic)abstract
- The low-lying excited states in the neutron-deficient N = Z + 1 nucleus 8743 Tc 44 have been studiedvia the fusion-evaporation reaction 54 Fe( 36 Ar, 2n1p) 87 Tc at the Grand Accélérateur National d’IonsLourds (GANIL), France. The AGATA spectrometer was used in conjunction with the auxiliaryNEDA, Neutron Wall, and DIAMANT detector arrays to measure coincident prompt γ-rays, neutrons, and charged particles emitted in the reaction. A level scheme of 87 Tc from the (9/2 +g.s. ) state to the (33/2 +)statewasestablishedbasedon6mutuallycoincidentγ-ray transitions. The con-1structed level structure exhibits a rotational behavior with a sharp back bending at ~ω ≈ 0.50 MeV. A decrease in alignment frequency and increase in alignment sharpness in the odd-mass isotonic chains around N = 44 is proposed as an effect of the enhanced isoscalar neutron-proton interactions in odd-mass nuclei when approaching the N = Z line.
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| 41. |
- Liu, X., et al.
(author)
-
Evidence for enhanced neutron-proton correlations from the levelstructure of the N= Z+ 1 nucleus 8743Tc44
- 2021
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 104:2
-
Journal article (peer-reviewed)abstract
- The low-lying excited states in the neutron-deficient N = Z + 1 nucleus (87)(43)Tcc(44) have been studied via the fusion-evaporation reaction Fe-54(Ar-36, 2n1p)Tc-87 at the Grand Accelerateur National d'Ions Lourds (GANIL), France. The AGATA spectrometer was used in conjunction with the auxiliary NEDA, Neutron Wall, and DIAMANT detector arrays to measure coincident prompt gamma rays, neutrons, and charged particles emitted in the reaction. A level scheme of Tc-87 from the (9/2(g.s.)(+)) state to the (33/2(1)(+)) state was established based on six mutually coincident gamma-ray transitions. The constructed level structure exhibits a rotational behavior with a sharp backbending at (h) over bar omega approximate to 0.50 MeV. A decrease in alignment frequency and increase in alignment sharpness in the odd-mass isotonic chains around N = 44 is proposed as an effect of the enhanced isoscalar neutron-proton interactions in odd-mass nuclei when approaching the N = Z line.
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| 42. |
- Liu, Xiaoyu, et al.
(author)
-
Evidence for spherical-oblate shape coexistence in Tc-87
- 2022
-
In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 106:3
-
Journal article (peer-reviewed)abstract
- Excited states in the neutron-deficient nucleus Tc-87 have been studied via the fusion-evaporation reaction 54Fe(36Ar, 2n1p) Tc-87 at 115 MeV beam energy. The AGATA gamma-ray spectrometer coupled to the DIAMANT, NEDA, and Neutron Wall detector arrays for light-particle detection was used to measure the prompt coincidence of gamma rays and light particles. Six transitions from the deexcitation of excited states belonging to a new band in Tc-87 were identified by comparing gamma-ray intensities in the spectra gated under different reaction channel selection conditions. The constructed level structure was compared with the shell model and total Routhian surface calculations. The results indicate that the new band structure in 87Tc is built on a spherical configuration, which is different from that assigned to the previously identified oblate yrast rotational band.
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| 43. |
- Siciliano, M., et al.
(author)
-
Pairing-quadrupole interplay in the neutron-deficient tin nuclei : First lifetime measurements of low-lying states in Sn-106,Sn-108
- 2020
-
In: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 806
-
Journal article (peer-reviewed)abstract
- The lifetimes of the low-lying excited states 2(+) and 4(+) have been directly measured in the neutron-deficient Sn-106,Sn-108 isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted gamma rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the B(E2; 2(1)(+) -> 0(g.s)(+)) values and it describes well the experimental pattern for Sn104-114 ; the B(E2;(+)(4) -> 2(1)(+)) values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in Sn-108.
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| 44. |
- Valiente-Dobon, J. J., et al.
(author)
-
Conceptual design of the AGATA 2 pi array at LNL
- 2023
-
In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1049
-
Journal article (peer-reviewed)abstract
- The Advanced GAmma Tracking Array (AGATA) has been installed at Laboratori Nazionali di Legnaro (LNL), Italy. In this installation, AGATA will consist, at the beginning, of 13 AGATA triple clusters (ATCs) with an angular coverage of 1n,and progressively the number of ATCs will increase up to a 2 pi angular coverage. This setup will exploit both stable and radioactive ion beams delivered by the Tandem-PIAVE-ALPI accelerator complex and the SPES facility. The new implementation of AGATA at LNL will be used in two different configurations, firstly one coupled to the PRISMA large-acceptance magnetic spectrometer and lately a second one at Zero Degrees, along the beam line. These two configurations will allow us to cover a broad physics program, using different reaction mechanisms, such as Coulomb excitation, fusion-evaporation, transfer and fission at energies close to the Coulomb barrier. These setups have been designed to be coupled with a large variety of complementary detectors such as charged particle detectors, neutron detectors, heavy-ion detectors, high-energy gamma-ray arrays, cryogenic and gasjet targets and the plunger device for lifetime measurements. We present in this paper the conceptual design, characteristics and performance figures of this implementation of AGATA at LNL.
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| 45. |
- Benzoni, G., et al.
(author)
-
First Measurement of Beta Decay Half-lives in Neutron-rich Tl and Bi Isotopes
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 715:4-5, s. 293-297
-
Journal article (peer-reviewed)abstract
- Neutron-rich isotopes around lead, beyond N = 126, have been studied exploiting the fragmentation of an uranium primary beam at the FRS-RISING setup at GSI. For the first time beta-decay half-lives of Bi-219 and Tl-211,Tl-212,Tl-213 isotopes have been derived. The half-lives have been extracted using a numerical simulation developed for experiments in high-background conditions. Comparison with state of the art models used in r-process calculations is given, showing a systematic underestimation of the experimental values, at variance from close-lying nuclei. (c) 2012 Elsevier B.V. All rights reserved.
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| 46. |
- Bracco, A, et al.
(author)
-
Search for the GDR built on superdeformed nuclei
- 2000
-
In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; T88, s. 182-188
-
Journal article (peer-reviewed)abstract
- An experiment aiming at finding evidence for gamma-decay of the giant dipole resonance built on superdeformed nuclear states has been made using the EUROBALL gamma-detector array coupled to the large BaF2 detectors of the HECTOR system. The reaction Pd-11
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| 47. |
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| 48. |
- Doornenbal, P., et al.
(author)
-
RISING: Gamma‐ray Spectroscopy with Radioactive Beams at GSI
- 2007
-
In: AIP Conference Proceedings. - : AIP. - 0094-243X. - 9780735413283 ; 891, s. 99-107
-
Conference paper (peer-reviewed)abstract
- The Rare Isotope Spectroscopic INvestigation at GSI (RISING) project is a major pan‐European collaboration. Its physics aims are the studies of exotic nuclear matter with abnormal proton‐to‐neutron ratios compared with naturally occurring isotopes. RISING combines the FRagment Separator (FRS) which allows relativistic energies and projectile fragmentation reactions with EUROBALL Ge Cluster detectors for γ spectroscopic research. The RISING setup can be used in two different configurations. Either the nuclei of interest are investigated after being stopped or the heavy ions hit a secondary target at relativistic energies and the thereby occurring excitations are studied. For the latter case, MINIBALL Ge detectors and the HECTOR array are used in addition. Example achievements of the Fast Beam setup are presented and compared to various shell model calculations, while for the Stopped Beam setup initial results are shown.
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| 49. |
- Gottardo, A., et al.
(author)
-
Isomeric Decay Spectroscopy of the 217Bi Isotope
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:3
-
Journal article (peer-reviewed)abstract
- The structure of the neutron-rich bismuth isotope 217Bi has been studied for the first time. The fragmentation of a primary 238U beam at the FRS-RISING setup at GSI was exploited to perform γ-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t1/2=3 μs isomer were observed, allowing one to establish the low-lying structure of 217Bi. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.
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| 50. |
- Gottardo, A., et al.
(author)
-
Isomers in Neutron-rich Lead Isotopes Populated via the Fragmentation of 238U at 1 GeV A
- 2011
-
In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 312
-
Journal article (peer-reviewed)abstract
- Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a 238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structure of neutron-rich nuclei around the Z=82 shell closure. Some preliminary results are reported in this paper.
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