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| 7. |
- Nilsson, Sven Gösta, et al.
(författare)
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Nuclei at very high angular momentum
- 1978
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Ingår i: Proceedings of the international conference on dynamical properties of heavy-ion reactions. ; 1978, s. 37-87
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Konferensbidrag (refereegranskat)
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| 8. |
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| 9. |
- Albertsson, Martin, et al.
(författare)
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Calculated fission-fragment mass yields and average total kinetic energies of heavy and superheavy nuclei
- 2020
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 56:2
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Tidskriftsartikel (refereegranskat)abstract
- Fission-fragment mass and total-kinetic-energy (TKE) distributions following fission of even-even nuclides in the region 74 ≤ Z≤ 126 and 92 ≤ N≤ 230 , comprising 896 nuclides have been calculated using the Brownian shape-motion method. The emphasis is the region of superheavy nuclei. To show compatibility with earlier results the calculations are extended to include earlier studied regions. An island of asymmetric fission is obtained in the superheavy region, 106 ≤ Z≤ 114 and 162 ≤ N≤ 176 , where the heavy fragment is found to be close to 208Pb and the light fragment adjusts accordingly. Most experimentally observed α-decay chains of superheavy nuclei with Z> 113 terminate by spontaneous fission in our predicted region of asymmetric fission. In these cases, the pronounced large asymmetry is accompanied by a low TKE value compatible with measurements.
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| 10. |
- Andersson, C G, et al.
(författare)
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Islands of high-spin yrast isomers
- 1978
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Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 309, s. 141-176
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Tidskriftsartikel (refereegranskat)
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| 11. |
- Andreoiu, Corina, et al.
(författare)
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Competing Decay-out Mechanisms of the Yrast Superdeformed Band in 59Cu
- 2004
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 701, s. 289-294
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Konferensbidrag (refereegranskat)abstract
- This contribution reports on the decay-out of the yrast superdeformed band in 59Cu. It decays by multiple γ-ray transitions into low-spin spherical states in the first minimum of the nuclear potential in 59Cu, and, in competition, by emitting two prompt protons into a spherical state in 58Ni. For the first time in A ~ 60, the role of doorway states in the course of the decay-out is discussed
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| 12. |
- Andreoiu, Corina, et al.
(författare)
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Doorway States in the Gamma Decay-out of the Yrast Superdeformed Band in 59Cu
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:23
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Tidskriftsartikel (refereegranskat)abstract
- The decay-out process of the yrast superdeformed band in Cu-59 has been investigated. The firm determination of spin, parity, excitation energy, and configuration of the states involved in this process constitutes a unique situation for a detailed understanding of the decay-out mechanism. A theoretical model is introduced that includes a residual interaction and tunneling matrix element between bands, calculated in the configuration-dependent cranked Nilsson-Strutinsky model. This interaction causes the decay to occur via a small number of observed doorway states.
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| 13. |
- Armstrong, Jeremy, et al.
(författare)
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Interaction Blockade and Pairing in Two-Dimensional Finite Fermion Systems
- 2009
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Ingår i: Few-body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 45:2-4, s. 219-222
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Konferensbidrag (refereegranskat)abstract
- The properties of two-component fermionic quantum systems in two dimensions, such as they nowadays may be realized with cold atoms in traps, are studied within the pairing model adapted from nuclear physics. We compare the results with those of a full numerical diagonalization of the many-body Hamiltonian. The chemical potential differences, excitation energies and angular momentum spectra show that when the zero-range attractive interaction is varied in strength, strong odd-even effects, gaps and shell structure emerge.
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| 14. |
- Armstrong, J. R., et al.
(författare)
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Complexity of quantum states in the two-dimensional pairing model
- 2012
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 86:6
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Tidskriftsartikel (refereegranskat)abstract
- It is known that many-fermion systems, such as complex atoms and nuclei, reveal (at some level of excitation energy) local signatures of quantum chaos similar to the predictions of random matrix theory. Here, we study the gradual development of such signatures in a model system of up to 16 fermions interacting through short-range pairing-type forces in a two-dimensional harmonic trap. We proceed from the simplest characteristics of the level spacing distribution to the complexity of eigenstates, strength, and correlation functions. For increasing pairing strength, at first, chaotic signatures gradually appear. However, when the pairing force dominates the Hamiltonian, we see a regression towards regularity. We introduce a "phase correlator" that allows us to distinguish the complexity of a quantum state that originates from its collective nature, from the complexity originating from quantum chaos. DOI: 10.1103/PhysRevE.86.066204
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| 15. |
- Bajpeyi, Awanish, et al.
(författare)
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Study of the (p, γ) and (α, γ) reactions for 96,98,104Ru and 112,114,116Sn at astrophysically relevant energies
- 2017
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Ingår i: Physics of Atomic Nuclei. - 1063-7788. ; 80:3, s. 402-411
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Tidskriftsartikel (refereegranskat)abstract
- Cross section and S factor of the proton- and alpha-induced reactions have been studied for the Ruthenium and tin isotopes in the effective energy range, i.e. Gamow window. These reactions are important for developing the understanding for nucleosynthesis, particularly for the synthesis of p nuclei (p process). In this work, cross sections and S factor have been calculated through TALYS in Hauser–Feshbach formalism using nuclear densities calculated in relativistic mean field (RMF) formalism. Calculated results of cross sections, S factor and nuclear structure have been compared with existing theoretical as well as experimental results available and are found to be in good agreement.
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| 16. |
- Borgh, Magnus, et al.
(författare)
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Correlation and spin polarization in quantum dots: Local spin density functional theory revisited
- 2005
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Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 105:6, s. 817-825
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Tidskriftsartikel (refereegranskat)abstract
- Using quantum dot artificial atoms as a simple toy model, we reflect on the question of whether spin density functional theory (SDFT) can accurately describe correlation effects in low-dimensional fermion systems. Different expressions for the local density approximation of the exchange-correlation energy for the two-dimensional electron gas, such as the much-used functional of Tanatar and Ceperley, and the recent suggestion by Attaccalite et al., are compared with the results of a numerical diagonalization of the many-body Hamiltonian matrix in the limit of small electron numbers. For systems with degeneracies, as shown in the present work for the example of a spin triplet with S = 1, the direct comparison with configuration interaction (Cl) methods demonstrates that the spin representation of SDFT may, under certain circumstances, produce artificial energy splittings between states that belong to the same spin multiplet. For a singlet ground state with S = S = 0, however, the correlation functions of the Cl solutions confirm the spin-density wave states found earlier within the SDFT method.
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| 17. |
- Carlsson, Gillis, et al.
(författare)
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How to calculate α-decay rates in the future?
- 2016
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Ingår i: Nobel Symposium NS 160 - Chemistry and Physics of Heavy and Superheavy Elements. - : EDP Sciences. - 9782759890118 ; 131
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Konferensbidrag (refereegranskat)abstract
- New elements discovered during past decades have been created in fusion reactions where a lighter nucleus is collided with a heavier one. The new elements created often decay by emitting α particles. From the half-lives of the decays and the energies of the emitted particles one may extract some properties of the new elements. In this talk the recent work performed by the Lund group to model α decay starting from nuclear density-functional theory is reviewed and a possible extension is mentioned.
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| 18. |
- Christensson, J, et al.
(författare)
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Effective-interaction approach to the many-boson problem
- 2009
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934 .- 1050-2947. ; 79:1, s. 012707-
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Tidskriftsartikel (refereegranskat)abstract
- We show that the convergence behavior of the many-body numerical diagonalization scheme for strongly interacting bosons in a trap can be significantly improved by the Lee-Suzuki method adapted from nuclear physics: One can construct an effective interaction that acts in a space much smaller than the original Hilbert space. In particular for short-ranged forces and strong correlations, the method offers a good estimate of the energy and the excitation spectrum, at a computational cost several orders of magnitude smaller than that required by the standard method.
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| 19. |
- Døssing, Thomas, et al.
(författare)
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Collective enhancements in nuclear level densities
- 2019
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 55:12
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Tidskriftsartikel (refereegranskat)abstract
- Contributions to the nuclear level density from a deformed core and from surface vibrations are discussed. The influence of symmetries of the nuclear shape is highlighted by quoting and discussing analytic Fermi gas level densities for irregular, deformed and spherical shapes. A thorough evaluation of the rotational enhancement factor to the level density is carried out for 17 well deformed rare-earth nuclei. Counted experimental levels are compared to levels obtained from the combinatorial level-density model, applying the Folded-Yukawa potential with BCS quasiparticle paring. It is found that the phase space of the rotating core contributes fully to the level density at the low energies where reliable information of experimental levels exists. The analysis is inspired by recent thermal Shell Model Monte Carlo results, which are also included in the comparison. The situation at the neutron excitation energy is also discussed, together with the conditions for vibrational enhancement. Experiments aimed at investigating the fade-away of collective enhancements are briefly discussed.
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| 20. |
- Døssing, T, et al.
(författare)
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Decay-Out Of Superdeformed Bands By Coupling To Ordered Or Chaotic Spectra
- 2005
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 764:1, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- Different treatments of the decay-out of superdeformed bands are reviewed, focusing on the role of the normally deformed doorway states to which the superdeformed band primarily couples at decay-out. A schematic description based on sparse GOE matrices is formulated for the normally deformed states including one doorway state. This allows for a gradual change of the normally deformed spectrum from an ordered to a chaotic situation by means of the effective dimensionality parameter. It is found that the distribution of the small normally deformed admixtures into the superdeformed band, through which it decays, depends sensitively on the effective dimensionality parameter. Analyzing the measured distribution of transition strength of decay-out gamma-ray lines in 194Hg, it is concluded that the spectrum of normally deformed states is closer to the chaotic than the ordered situation at the energy and angular momentum of the superdeformed band. ©2005 American Institute of Physics
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| 21. |
- Døssing, T, et al.
(författare)
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Order to Chaos Properties of the Decay-out Gamma Rays from Superdeformed Bands
- 2004
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. ; 701, s. 164-168
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Tidskriftsartikel (refereegranskat)abstract
- Based on GOE sparse matrices, a model for decay-out of superdeformed bands is formulated, with focus on the degree of chaoticity of the spectrum of normally deformed states, to which the superdeformed band couples at decay-out. By means of the effective dimensionality parameter, the spectrum may be varied between the two limiting situations of complete order and complete chaos. The model is applied to the measured distribution of transition strength of decay-out gamma-ray lines in 194Hg, and it is found that the normally deformed states should be closer to the chaotic than the ordered situation, with GOE-type spectral correlations extending over at least 10 levels. ©2004 American Institute of Physics
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| 22. |
- Forsberg, U., et al.
(författare)
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Recoil-α-fission and recoil-α-α-fission events observed in the reaction 48Ca + 243Am
- 2016
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 953, s. 117-138
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Tidskriftsartikel (refereegranskat)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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| 23. |
- Forsberg, Ulrika, et al.
(författare)
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Spectroscopic Tools Applied to Element Z = 115 Decay Chains
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X .- 2101-6275. - 9782759811755 - 9782759811762 ; 66, s. 02036-02036
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Konferensbidrag (refereegranskat)abstract
- Nuclides that are considered to be isotopes of element Z = 115 were produced in the reaction 48Ca + 243Am at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt. The detector setup TASISpec was used. It was mounted behind the gas-filled separator TASCA. Thirty correlated α-decay chains were found, and the energies of the particles were determined with high precision. Two important spectroscopic aspects of the offline data analysis are discussed in detail: the handling of digitized preamplified signals from the silicon strip detectors, and the energy reconstruction of particles escaping to upstream detectors relying on pixel-by-pixel dead-layer thicknesses.
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| 24. |
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| 25. |
- Forssen, Christian, 1974, et al.
(författare)
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The Ab Initio No-core Shell Model
- 2009
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 45:2, s. 111-
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Konferensbidrag (refereegranskat)abstract
- This contribution reviews a number of applications of the ab initio no-core shell model (NCSM) within nuclear physics and beyond. We will highlight a nuclear-structure study of the A = 12 isobar using a chiral NN + 3NF interaction. In the spirit of this workshop we will also mention the new development of the NCSM formalism to describe open channels and to approach the problem of nuclear reactions. Finally, we will illustrate the universality of the many-body problem by presenting the recent adaptation of the NCSM effective-interaction approach to study the many-boson problem in an external trapping potential with short-range interactions.This article is based on the presentation by C. Forssén at the Fifth Workshop on Critical Stability, Erice, Sicily.
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| 26. |
- Grönqvist, Johan, et al.
(författare)
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Strain in semiconductor core-shell nanowires
- 2009
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 106:5
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Tidskriftsartikel (refereegranskat)abstract
- We compute strain distributions in core-shell nanowires of zinc blende structure. We use both continuum elasticity theory and an atomistic model, and consider both finite and infinite wires. The atomistic valence force-field (VFF) model has only few assumptions. But it is less computationally efficient than the finite-element (FE) continuum elasticity model. The generic properties of the strain distributions in core-shell nanowires obtained based on the two models agree well. This agreement indicates that although the calculations based on the VFF model are computationally feasible in many cases, the continuum elasticity theory suffices to describe the strain distributions in large core-shell nanowire structures. We find that the obtained strain distributions for infinite wires are excellent approximations to the strain distributions in finite wires, except in the regions close to the ends. Thus, our most computationally efficient model, the FE continuum elasticity model developed for infinite wires, is sufficient, unless edge effects are important. We give a comprehensive discussion of strain profiles. We find that the hydrostatic strain in the core is dominated by the axial strain-component, epsilon(ZZ). We also find that although the individual strain components have a complex structure, the hydrostatic strain shows a much simpler structure. All in-plane strain components are of similar magnitude. The nonplanar off-diagonal strain components (epsilon(XZ) and epsilon(YZ)) are small but nonvanishing. Thus the material is not only stretched and compressed but also warped. The models used can be extended for the study of wurtzite nanowire structures, as well as nanowires with multiple shells.
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| 27. |
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| 28. |
- Juodagalvis, A., et al.
(författare)
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Cranked Nilsson-Strutinsky vs the spherical shell model: A comparative study of pf-shell nuclei
- 2006
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Ingår i: Physical Review C: covering nuclear physics. ; 73, s. 1-044327
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Tidskriftsartikel (refereegranskat)abstract
- A comparative study is performed of a deformed mean field theory, represented by the cranked Nilsson-Strutinsky (CNS) model and the spherical shell model. Energy spectra, occupation numbers, B(E2) values, and spectroscopic quadrupole moments in the light pf-shell nuclei are calculated in the two models and compared. The result is also compared to available experimental data which are generally well described by the shell model. Although the Nilsson-Strutinsky calculation does not include pairing, both the subshell occupation numbers and quadrupole properties are found to be rather similar in the two models. It is also shown that "unpaired" shell model calculations produce energies similar to those from the CNS. The role of the pairing energy in the description of backbending and signature splitting in odd-mass nuclei is also discussed.
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| 29. |
- Juodagalvis, Andrius, et al.
(författare)
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Pairing and signature splitting in pf-shell nuclei
- 2006
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Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 198-199
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Tidskriftsartikel (refereegranskat)abstract
- A comparative study of light pf shell nuclei using cranked Nilsson-Strutinsky model and the spherical shell model indicates that some of the signature splitting between the partner bands in odd-A nuclei originates from a gradual decrease in the contents of the pairing energy as spin increases.
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| 30. |
- Karlsson, Lennart B., et al.
(författare)
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Identical bands in superdeformed nuclei
- 1998
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 416:1-2, s. 16-22
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Tidskriftsartikel (refereegranskat)abstract
- Using the configuration constrained, cranked Nilsson-Strutinsky model, we point to a mechanism that could explain why identical bands are much more likely to occur in superdeformed than in normal-deformed nuclei. The role of the high-N orbitals in the superdeformed configuration is stressed, and correlated with the observed peaks in the fractional change distribution of the script J sign(2) moment of inertia. Also (fractional) changes of the electric quadrupole moment due to changes of the high-N content are discussed.
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| 31. |
- Kohler, Heiner, et al.
(författare)
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Coupling coefficient distribution in the doorway mechanism
- 2010
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- In many-body and other systems, the physics situation often allows one to interpret certain, distinct states by means of a simple picture. In this interpretation, the distinct states are not eigenstates of the full Hamiltonian. Hence, there is an interaction that makes the distinct states act as doorways into background states which are modeled statistically. The crucial quantities are the overlaps between the eigenstates of the full Hamiltonian and the doorway states, that is, the coupling coefficients occurring in the expansion of true eigenstates in the simple model basis. Recently, the distribution of the maximum coupling coefficients was introduced as a new, highly sensitive statistical observable. In the particularly important regime of weak interactions, this distribution is very well approximated by the fidelity distribution, defined as the distribution of the overlap between the doorway states with interaction and without interaction. Using a random matrix model, we calculate the latter distribution exactly for regular and chaotic background states in the cases of preserved and fully broken time-reversal invariance. We also perform numerical simulations and find excellent agreement with our analytical results.
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| 32. |
- Kohler, Heiner, et al.
(författare)
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Exact fidelity and full fidelity statistics in regular and chaotic surroundings
- 2010
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 81:5
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Tidskriftsartikel (refereegranskat)abstract
- For a prepared state exact expressions for the time-dependent mean fidelity as well as for the mean inverse participation ratio are obtained analytically. The prepared state is taken as an eigenstate of the unperturbed system, and the studied fidelity is identical to the survival probability. The full distribution functions of fidelity in the long-time limit and of inverse participation ratio are studied numerically and analytically. Surprising features such as fidelity revival and nonergodicity are observed. The roles of the coupling coefficients and of complexity of background are studied as well.
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| 33. |
- Kohler, Heiner, et al.
(författare)
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Survival probability of a doorway state in regular and chaotic environments
- 2010
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:21
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the survival probability of a special state which couples randomly to a regular or chaotic environment. The environment is modeled by a suitably chosen random matrix ensemble. The exact results exhibit non-perturbative features as revival of probability and non-ergodicity. The role of background complexity and coupling complexity is discussed as well.
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| 34. |
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| 35. |
- Moller, Peter, et al.
(författare)
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Heavy-element fission barriers
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:6
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Forskningsöversikt (refereegranskat)abstract
- We present calculations of fission properties for heavy elements. The calculations are based on the macroscopic-microscopic finite-range liquid-drop model with a 2002 parameter set. For each nucleus we have calculated the potential energy in three different shape parametrizations: (1) for 5 009 325 different shapes in a five-dimensional deformation space given by the three-quadratic-surface parametrization, (2) for 10 850 different shapes in a three-dimensional deformation space spanned by epsilon(2), epsilon(4), and gamma in the Nilsson perturbed-spheroid parametrization, supplemented by a densely spaced grid in epsilon(2), epsilon(3), epsilon(4), and epsilon(6) for axially symmetric deformations in the neighborhood of the ground state, and (3) an axially symmetric multipole expansion of the shape of the nuclear surface using beta(2), beta(3), beta(4), and beta(6) for intermediate deformations. For a fissioning system, it is always possible to define uniquely one saddle or fission threshold on the optimum trajectory between the ground state and separated fission fragments. We present such calculated barrier heights for 1585 nuclei from Z=78 to Z=125. Traditionally, actinide barriers have been characterized in terms of a "double-humped" structure. Following this custom we present calculated energies of the first peak, second minimum, and second peak in the barrier for 135 actinide nuclei from Th to Es. However, for some of these nuclei which exhibit a more complex barrier structure, there is no unique way to extract a double-humped structure from the calculations. We give examples of such more complex structures, in particular the structure of the outer barrier region near Th-232 and the occurrence of multiple fission modes. Because our complete results are too extensive to present in a paper of this type, our aim here is limited: (1) to fully present our model and the methods for determining the structure of the potential-energy surface, (2) to present fission thresholds for a large number of heavy elements, (3) to compare our results with the two-humped barrier structure deduced from experiment for actinide nuclei, and (4) to compare to additional fission-related data and other fission models..
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| 36. |
- Olofsson, Henrik, et al.
(författare)
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Semiclassical Theory of Bardeen-Cooper-Schrieffer Pairing-Gap Fluctuations
- 2008
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Ingår i: Physical Review Letters. - 1079-7114. ; 100:3
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Tidskriftsartikel (refereegranskat)abstract
- uperfluidity and superconductivity are genuine many-body manifestations of quantum coherence. For finite-size systems the associated pairing gap fluctuates as a function of size or shape. We provide a theoretical description of the zero temperature pairing fluctuations in the weak-coupling BCS limit of mesoscopic systems characterized by order or chaos dynamics. The theory accurately describes experimental observations of nuclear superfluidity (regular system), predicts universal fluctuations of superconductivity in small chaotic metallic grains, and provides a global analysis in ultracold Fermi gases.
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| 37. |
- Puig von Friesen, Marc, et al.
(författare)
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Quantum chaos and regularity in ultracold Fermi gases
- 2007
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - : American Physical Society. - 1539-3755 .- 1550-2376. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- Quantum fluctuation of the energy is studied for an ultracold gas of interacting fermions trapped in a three-dimensional potential. Periodic-orbit theory is explored, and energy fluctuations are studied versus the particle number for generic regular and chaotic systems, as well as for a system defined by a harmonic confinement potential. Temperature effects on the energy fluctuations are investigated.
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| 38. |
- Radionov, Sergey, et al.
(författare)
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Nuclear friction and quantum mechanical diffusion
- 2005
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:6
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Tidskriftsartikel (refereegranskat)abstract
- We study dissipative properties of the motion of a slow nuclear collective variable weakly coupled to a complex quantum environment formed by the fast nucleonic degrees of freedom. The fast quantum mechanical subsystem is treated within the random matrix approach, where the complexity of the nucleonic degrees of freedom's motion can be changed by a parameter from regular to fully chaotic. Classical dynamics is assumed for the slow variable, and the equation of motion is determined from conservation of the total energy of the nuclear many-body system. We show that the macroscopic equation of motion for the collective variable is subject to a memory-dependent friction force, with a retardation defined by the chaoticity of the fast nucleonic environment.
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| 39. |
- Radionov, Sergey, et al.
(författare)
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Regularity and chaos in interacting two-body systems
- 2004
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Ingår i: Physical Review E. - 1063-651X. ; 70:3
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Tidskriftsartikel (refereegranskat)abstract
- We study classical and quantum chaos for two interacting particles on the plane. This is the simplest nontrivial case which sheds light on chaos in interacting many-body systems. The system consists of a confining one-body potential, assumed to be a deformed harmonic oscillator, and a two-body interaction of Coulomb type. In general, the dynamics is mixed with regular and chaotic trajectories. The relative roles of the one-body field and the two-body interaction are investigated. Chaos sets in as the strength of the two-body interaction increases. However, the degree of chaoticity strongly depends on the shape of the one-body potential and, for some shapes of the harmonic oscillator, the dynamics remains regular for all values of the two-body interaction. Scaling properties are found for the classical as well as for the quantum mechanical problem.
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| 40. |
- Ragnarsson, Ingemar, et al.
(författare)
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Complete Spectroscopy in High-spin Cranking Calculations
- 2004
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 20:1, s. 35-36
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Tidskriftsartikel (refereegranskat)abstract
- Exact and approximate quantum numbers of the cranked Nilsson-Strutinsky (CNS) formalism are exploited to calculate excited bands in fixed configurations with the energy of the individual bands minimized with respect to deformation for all spin values. The formalism is applied to Cu-59, where all bands which appear important in the decay out of the superdeformed band are calculated.
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| 41. |
- Ragnarsson, Ingemar, et al.
(författare)
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Excited Bands in Fixed CNS Configurations
- 2003
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 656, s. 205-210
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Konferensbidrag (refereegranskat)abstract
- Exact and approximate quantum numbers of the cranked Nilsson-Strutinsky (CNS) formalism are exploited to calculate excited bands in fixed configurations with the energy of the individual bands minimized with respect to deformation for all spin values. The formalism is illustrated to calculate all bands which appear important in the decay out of the superdeformed band in 59Cu
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| 42. |
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| 43. |
- Randrup, Jørgen, et al.
(författare)
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Fission dynamics with microscopic level densities
- 2018
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Ingår i: Scientific Workshop on "Nuclear Fission and the Emission of Prompt Neutrons and Gamma Rays", THEORY 2017. - : EDP Sciences. - 9782759890316 ; 169
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Konferensbidrag (refereegranskat)abstract
- Working within the Langevin framework of nuclear shape dynamics, we study the dependence of the evolution on the degree of excitation. As the excitation energy of the fissioning system is increased, the pairing correlations and the shell effects diminish and the effective potential-energy surface becomes ever more liquid-drop like. This feature can be included in the treatment in a formally well-founded manner by using the local level densities as a basis for the shape evolution. This is particularly easy to understand and implement in the Metropolis treatment where the evolution is simulated by means of a random walk on the five-dimensional lattice of shapes for which the potential energy has been tabulated. Because the individual steps between two neighboring lattice sites are decided on the basis of the ratio of the statistical weights, what is needed is the ratio of the local level densities for those shapes, evaluated at the associated local excitation energies. For this purpose, we adapt a recently developed combinatorial method for calculating level densities which employs the same single-particle levels as those that were used for the calculation of the pairing and shell contributions to the macroscopic-microscopic deformation-energy surface. For each nucleus under consideration, the level density (for a fixed total angular momentum) is calculated microscopically for each of the over five million shapes given in the three-quadratic-surface parametrization. This novel treatment, which introduces no new parameters, is illustrated for the fission fragment mass distributions for selected uranium and plutonium cases.
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| 44. |
- Rontani, Massimo, et al.
(författare)
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Cold Fermionic Atoms in Two-Dimensional Traps: Pairing versus Hund's Rule
- 2009
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Ingår i: Physical Review Letters. - 1079-7114. ; 102:6, s. 1-060401
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Tidskriftsartikel (refereegranskat)abstract
- The microscopic properties of few interacting cold fermionic atoms confined in a two-dimensional (2D) harmonic trap are studied by numerical diagonalization. For repulsive interactions, a strong shell structure dominates, with Hund's rule acting at its extreme for the midshell configurations. In the attractive case, odd-even oscillations due to pairing occur simultaneously with deformations in the internal structure of the ground states, as seen from pair correlation functions.
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| 45. |
- Rudolph, Dirk, et al.
(författare)
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58Ni: An Unpaired Band Crossing at New Heights of Angular Momentum for Rotating Nuclei
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 96:9
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Ni-58 have been investigated by means of the fusion-evaporation reaction Si-28(S-32,2p)Ni-58 at 130 MeV beam energy. Discrete-energy levels are observed in Ni-58 at record-breaking 42 MeV excitation energy and angular momenta in excess of 30h. The states form regular rotational bands with unprecedented high rotational frequencies. A comparison with configuration dependent cranked Nilsson-Strutinsky calculations reveals an exceptional two-band crossing scenario, the interaction strength of which is strongly shape dependent.
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| 46. |
- Rudolph, Dirk, et al.
(författare)
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Alpha-Photon Coincidence Spectroscopy Along Element 115 Decay Chains
- 2014
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Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 45, s. 263-272
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Tidskriftsartikel (refereegranskat)abstract
- Produced in the reaction 48Ca+243Am, thirty correlated α-decay chains were observed in an experiment conducted at the GSI Helmholzzentrum für Schwerionenforschung, Darmstadt, Germany. The decay chains are basically consistent with previous findings and are considered to originate from isotopes of element 115 with mass numbers 287, 288, and 289. A set-up aiming specifically for high-resolution charged particle and photon coincidence spectroscopy was placed behind the gas-filled separator TASCA. For the first time, γ rays as well as X-ray candidates were observed in prompt coincidence with the α-decay chains of element 115.
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| 47. |
- Rudolph, Dirk, et al.
(författare)
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Editorial
- 2016
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Ingår i: Nobel Symposium NS 160 – Chemistry and Physics of Heavy and Superheavy Elements : EPJ Web of Conferences - EPJ Web of Conferences. - : EDP Sciences. - 9782759890118 ; 131, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 48. |
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| 49. |
- Rudolph, Dirk, et al.
(författare)
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Selected Spectroscopic Results on Element 115 Decay Chains
- 2015
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 303:2, s. 1185-1190
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Tidskriftsartikel (refereegranskat)abstract
- Thirty correlated alpha-decay chains were observed in an experiment studying the fusion-evaporation reaction 48Ca + 243Am at the GSI Helmholtzzentrum f¨ur Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution alpha-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the ‘Island of Stability’ with unprecedented experimental precision.
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| 50. |
- Rudolph, Dirk, et al.
(författare)
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Spectroscopy of Element 115 Decay Chains
- 2013
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Ingår i: Physical Review Letters. - 1079-7114. ; 111:11
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Tidskriftsartikel (refereegranskat)abstract
- A high-resolution , X-ray and gamma-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated alpha-decay chains were detected following the fusion-evaporation reaction 48Ca + 243Am. The observations are consistent with previous assignments of similar decay chains to originate from element Z = 115. For the first time, precise spectroscopy allows the derivation of excitation schemes of isotopes along the decay chains starting with elements Z > 112. Comprehensive Monte-Carlo simulations accompany the data analysis. Nuclear structure models provide a first level interpretation.
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