| 1. |
- Johnson, Calvin W., et al.
(author)
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White paper: From bound states to the continuum
- 2020
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In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:12
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Research review (peer-reviewed)abstract
- This white paper reports on the discussions of the 2018 Facility for Rare Isotope Beams Theory Alliance (FRIB-TA) topical program ‘From bound states to the continuum: Connecting bound state calculations with scattering and reaction theory’. One of the biggest and most important frontiers in nuclear theory today is to construct better and stronger bridges between bound state calculations and calculations in the continuum, especially scattering and reaction theory, as well as teasing out the influence of the continuum on states near threshold. This is particularly challenging as many-body structure calculations typically use a bound state basis, while reaction calculations more commonly utilize few-body continuum approaches. The many-body bound state and few-body continuum methods use different language and emphasize different properties. To build better foundations for these bridges, we present an overview of several bound state and continuum methods and, where possible, point to current and possible future connections.
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| 2. |
- Koszorús, Agota, et al.
(author)
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Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32
- 2021
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In: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 17:4, s. 439-443
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Journal article (peer-reviewed)abstract
- Nuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 (refs. 1–3) in the calcium region, whereas the unexpectedly large increases in the charge radii4,5 open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with β-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond N = 32. Here we provide a charge radius measurement of 52K. It does not show a signature of magic behaviour at N = 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd–even variations in charge radii but not the notable increase beyond N = 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd–even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory.
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| 3. |
- Rudolph, Dirk, et al.
(author)
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Rotational Bands in the Doubly Magic Nucleus 56Ni
- 1999
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In: Physical Review Letters. - 1079-7114. ; 82:19, s. 3763-3766
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Journal article (peer-reviewed)abstract
- Structures of the medium- to high-spin states in the doubly magic nucleus Ni-56 have been investigated using the reaction Si-28(Ar-36, 2 alpha) and the gamma-ray spectrometer Gammasphere in conjunction with the 4 pi charged-particle detector array Microball. Two well-deformed rotational bands have been identified. There is evidence that one of the bands, which is identical to a sequence in the odd-odd neighbor Cu-58, partially decays via proton emission into the ground state of Co-55. Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data.
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| 4. |
- Ekstrom, A., et al.
(author)
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Accurate nuclear radii and binding energies from a chiral interaction
- 2015
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 91:5
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Journal article (peer-reviewed)abstract
- With the goal of developing predictive ab initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLOsat, yield accurate binding energies and radii of nuclei up to Ca-40, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective J(pi) = 3(-) states in O-16 and 40Ca are described accurately, while spectra for selected p- and sd-shell nuclei are in reasonable agreement with experiment.
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| 5. |
- Ekstrom, A., et al.
(author)
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Optimized Chiral Nucleon-Nucleon Interaction at Next-to-Next-to-Leading Order
- 2013
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:19, s. Art. no. 192502-
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Journal article (peer-reviewed)abstract
- We optimize the nucleon-nucleon interaction from chiral effective field theory at next-to-next-to-leading order (NNLO). The resulting new chiral force NNLOopt yields chi(2) approximate to 1 per degree of freedom for laboratory energies below approximately 125 MeV. In the A = 3, 4 nucleon systems, the contributions of three-nucleon forces are smaller than for previous parametrizations of chiral interactions. We use NNLOopt to study properties of key nuclei and neutron matter, and we demonstrate that many aspects of nuclear structure can be understood in terms of this nucleon-nucleon interaction, without explicitly invoking three-nucleon forces.
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| 6. |
- Forsberg, U., et al.
(author)
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Recoil-α-fission and recoil-α-α-fission events observed in the reaction 48Ca + 243Am
- 2016
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In: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 953, s. 117-138
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Journal article (peer-reviewed)abstract
- Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z=115, two recoil-α-fission and five recoil-α-α-fission events were observed. The latter five chains are similar to four such events reported from experiments performed at the Dubna gas-filled separator, and three such events reported from an experiment at the Berkeley gas-filled separator. The four chains observed at the Dubna gas-filled separator were assigned to start from the 2n-evaporation channel 289115 due to the fact that these recoil-α-α-fission events were observed only at low excitation energies. Contrary to this interpretation, we suggest that some of these recoil-α-α-fission decay chains, as well as some of the recoil-α-α-fission and recoil-α-fission decay chains reported from Berkeley and in this article, start from the 3n-evaporation channel 288115.
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| 7. |
- Forssen, Christian, 1974, et al.
(author)
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Living on the edge of stability, the limits of the nuclear landscape
- 2013
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In: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; T152:T152, s. 014022-
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Journal article (peer-reviewed)abstract
- A first-principles description of nuclear systems along the drip lines presents a substantial theoretical and computational challenge. In this paper, we discuss the nuclear theory roadmap, some of the key theoretical approaches, and present selected results with a focus on long isotopic chains. An important conclusion, which consistently emerges from these theoretical analyses, is that three-nucleon forces are crucial for both global nuclear properties and detailed nuclear structure, and that many-body correlations due to the coupling to the particle continuum are essential as one approaches particle drip lines. In the quest for a comprehensive nuclear theory, high performance computing plays a key role.
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| 8. |
- Hagen, G., et al.
(author)
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Neutron and weak-charge distributions of the Ca-48 nucleus
- 2016
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In: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 12:2, s. 186-190
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Journal article (peer-reviewed)abstract
- What is the size of the atomic nucleus? This deceivably simple question is difficult to answer. Although the electric charge distributions in atomic nuclei were measured accurately already half a century ago, our knowledge of the distribution of neutrons is still deficient. In addition to constraining the size of atomic nuclei, the neutron distribution also impacts the number of nuclei that can exist and the size of neutron stars. We present an ab initio calculation of the neutron distribution of the neutron-rich nucleus Ca-48. We show that the neutron skin (difference between the radii of the neutron and proton distributions) is significantly smaller than previously thought. We also make predictions for the electric dipole polarizability and the weak form factor; both quantities that are at present targeted by precision measurements. Based on ab initio results for Ca-48, we provide a constraint on the size of a neutron star.
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| 9. |
- Satula, Wojtek, et al.
(author)
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Isospin Mixing in Nuclei around N similar or equal to Z and the Superallowed beta-decay
- 2011
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In: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 42:3-4, s. 415-425
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Journal article (peer-reviewed)abstract
- Theoretical approaches that use one-body densities as dynamical variables, such as Hartree-Fock or the density functional theory (DFT), break isospin symmetry both explicitly, by virtue of charge-dependent interactions, and spontaneously. To restore the spontaneously broken isospin symmetry, we implemented the isospin-projection scheme on top of the Skyrme-DFT approach. This development allows for consistent treatment of isospin mixing in both ground and exited nuclear states. In this study, we apply this method to evaluate the isospin impurities in ground states of even-even and odd-odd N similar or equal to Z nuclei. By including simultaneous isospin and angular-momentum projection, we compute the isospin-breaking corrections to the 0(+) -> 0(+) superallowed beta-decay.
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| 10. |
- Shi, Yue, et al.
(author)
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Structure of Superheavy Nuclei Along Decay Chains of Element 115
- 2014
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:1
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Journal article (peer-reviewed)abstract
- A recent high-resolution α, X-ray, and γ-ray coincidence-spectroscopy experiment offered the first glimpse of excitation schemes of isotopes along α-decay chains of Z=115. To understand these observations and to make predictions about shell structure of superheavy nuclei below 288-115, we employ two complementary mean-field models: the self-consistent Skyrme energy density functional approach and the macroscopic-microscopic Nilsson model. We discuss the spectroscopic information carried by the new data. In particular, candidates for the experimentally observed E1 transitions in Mt276 are proposed. We find that the presence and nature of low-energy E1 transitions in well-deformed nuclei around Z=110,N=168 strongly depends on the strength of the spin-orbit coupling; hence, it provides an excellent constraint on theoretical models of superheavy nuclei. To clarify competing theoretical scenarios, an experimental search for E1 transitions in odd-A systems Mt277, Hs275, and Ds277 is strongly recommended.
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