| 1. |
- 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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| 2. |
- Almosly, W., et al.
(författare)
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Charged-current neutrino and antineutrino scattering off Cd-116 described by Skyrme forces
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:2, s. 024308-
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Tidskriftsartikel (refereegranskat)abstract
- We perform calculations of the cross sections for charged-current neutrino and antineutrino scattering off Cd-116 using ten different Skyrme interactions, at energies typical of supernova neutrinos. We use the quasiparticle random-phase approximation in its charged-changing mode (pnQRPA) to construct the required nuclear wave functions for the participant initial and final states. We compare the results of these calculations with the results of calculations based on the Bonn one-boson-exchange potential. The response of Cd-116 to supernova neutrinos is calculated by folding the obtained cross sections with suitably parametrized Fermi-Dirac distributions of the electron-neutrino and electron-antineutrino energies.
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| 3. |
- Almosly, W., et al.
(författare)
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Theoretical estimates of supernova-neutrino cross sections for the stable even-even lead isotopes : Charged-current reactions
- 2016
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Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 94:4
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Tidskriftsartikel (refereegranskat)abstract
- A detailed study of the charged-current supernova electron neutrino and electron antineutrino scattering off the stable even-mass lead isotopes A=204, 206, and 208 is reported in this work. The proton-neutron quasiparticle random-phase approximation (pnQRPA) is adopted to construct the nuclear final and initial states. Three different Skyrme interactions are tested for their isospin and spin-isospin properties and then applied to produce (anti)neutrino-nucleus scattering cross sections for (anti)neutrino energies below 80 MeV. Realistic estimates of the nuclear responses to supernova (anti)neutrinos are computed by folding the computed cross sections with a two-parameter Fermi-Dirac distribution of the electron (anti)neutrino energies. The computed cross sections are compared with earlier calculations and the analyses are extended to take into account the effects coming from the neutrino oscillations.
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| 4. |
- Andersson, Lise-Lotte, et al.
(författare)
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Classification of Superdeformed Bands in the Mass A~60 Region
- 2008
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Ingår i: Nuclear Physics and Astrophysics. - : AIP. - 9780735406032 ; 1072, s. 211-214
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Konferensbidrag (refereegranskat)abstract
- The experimental knowledge of the Cu-61(29)32 and Zn-61(30)31 nuclei has been largely extended via the joint results from three experiments. The fusion-evaporation reaction used a Ar-36 beam and a Si-28 target foil to produce the two nuclei via the evaporation of either three protons (Cu-61) or two protons and a neutron (Zn-61). The experimental set-ups comprised the Ge-array GAMMASPHERE as well as neutron and charged-particle detectors placed around the target position. The resulting level schemes include around ten rotational superdeformed structures in each isotope. Most of them are linked to normally deformed states and in many cases spins and parities of the low-lying states in each structure have been determined. The collective structures are compared with results from configuration dependent Cranked Nilsson-Strutinsky calculations. The different structures are in general well understood from the calculation but the results do also suggest modifications of the standard Nilsson parameters in the mass A similar to 60 region.
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| 5. |
- Andersson, Lise-Lotte, et al.
(författare)
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Extensive Gamma-ray Spectroscopy of Normally and Superdeformed Structures in 61Cu
- 2008
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 36:3, s. 251-278
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Tidskriftsartikel (refereegranskat)abstract
- A largely extended experimental knowledge of the Cu-61(29)32 nucleus has been obtained from three experiments. Excited states in Cu-61 were produced via the fusion-evaporation reaction Si-28(Ar-36, 3p)Cu-61. In addition to the Ge array GAMMASPHERE, neutron and charged-particle detectors placed around the target position were used for high-performance particle spectroscopy. The constructed level scheme includes more than 160 energy levels and 320 gamma-ray transitions belonging to both normally deformed as well as superdeformed rotational structures. The multipolarities have been determined for the gamma-ray transitions and as a result spin-parity assignments are given for nearly all energy levels. Experimental results in the normally deformed region are compared with predictions from large-scale shell model calculations. The collective structures are compared with results from cranked Nilsson-Strutinsky calculations. The results reveal the need to modify the standard Nilsson parameters in the mass A similar to 60 region.
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| 6. |
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| 7. |
- Carlsson, Gillis, et al.
(författare)
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Calculating the nuclear mass in the very high angular momentum regime
- 2006
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 74:1
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Tidskriftsartikel (refereegranskat)abstract
- Macroscopic-microscopic methods are applied in the high-spin regime to calculate the nuclear binding energy ("mass") as a function of proton number, neutron number, and angular momentum. Masses at high spin are calculated using the cranked Nilsson-Strutinsky model together with two different liquid drop models, the Lublin-Strasbourg drop model and the finite range liquid drop model. When comparisons are made with experimental data, a similar agreement between theory and experiment is obtained as for ground-state masses.
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| 8. |
- Carlsson, Gillis, et al.
(författare)
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Calculations of nuclear masses at finite angular momenta
- 2006
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Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 130-133
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Tidskriftsartikel (refereegranskat)abstract
- The macroscopic-microscopic method to calculate nuclear masses is extended into the high-spin regime in order to calculate the nuclear binding energy as a function of proton number, neutron number and angular momentum. We describe the method and exemplify it on recent experimental data.
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| 9. |
- Carlsson, Gillis, et al.
(författare)
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Collective vibrational states within the fast iterative quasiparticle random-phase approximation method
- 2012
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- An iterative method we previously proposed to compute nuclear strength functions [Toivanen et al., Phys. Rev. C 81, 034312 (2010)] is developed to allow it to accurately calculate properties of individual nuclear states. The approach is based on the quasiparticle random-phase approximation (QRPA) and uses an iterative non-Hermitian Arnoldi diagonalization method where the QRPA matrix does not have to be explicitly calculated and stored. The method gives substantial advantages over conventional QRPA calculations with regards to the computational cost. The method is used to calculate excitation energies and decay rates of the lowest-lying 2(+) and 3(-) states in Pb, Sn, Ni, and Ca isotopes using three different Skyrme interactions and a separable Gaussian pairing force.
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| 10. |
- Carlsson, Gillis, et al.
(författare)
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Fluctuating parts of nuclear ground-state correlation energies
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions. Purpose: Investigate the influence of higher-order correlation effects on nuclear binding energies using Skyrme's effective interaction. Methods: A cutoff in relative momenta is introduced to remove ultraviolet divergencies caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation and second-order many-body perturbation theory. Result: Contributions to the correlation energies are evaluated for several isotopic chains and an attempt is made to disentangle which parts give rise to fluctuations that may be difficult to incorporate on the HFB level. The dependence of the results on the cutoff is also investigated. Conclusions: The improved interaction allows explicit summations of perturbation series, which is useful for the description of some nuclear observables. However, refits of the interaction parameters are needed to obtain more quantitative results.
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| 11. |
- 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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| 12. |
- Carlsson, Gillis, et al.
(författare)
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Low-lying states in near-magic odd-odd nuclei and the effective interaction
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:5
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Tidskriftsartikel (refereegranskat)abstract
- The iterative quasiparticle random-phase approximation (QRPA) method we previously developed [Phys. Rev. C 81, 034312 (2010); 86, 024303 (2012); 86, 014307 (2012)] to accurately calculate properties of individual nuclear states is extended so that it can be applied for nuclei with odd numbers of neutrons and protons. The approach is based on the proton-neutron QRPA (pnQRPA) and uses an iterative non-Hermitian Arnoldi diagonalization method where the QRPA matrix does not have to be explicitly calculated and stored. The method is used to calculate excitation energies of proton-neutron multiplets for several nuclei. The influence of a pairing interaction in the T = 0 channel is studied.
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| 13. |
- Carlsson, Gillis, et al.
(författare)
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Many-particles-plus-rotor description of magnetic bands at high spin
- 2006
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 74:4
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Tidskriftsartikel (refereegranskat)abstract
- The high-spin parts of shears bands observed in Pb-198,Pb-199 are described by coupling several valence particles to a deformed rotor core. To give the model enough freedom so that both the proton and the neutron spin vectors can find their preferred direction, the use of five to six valence particles and holes is found to be necessary. Effective parameters characterizing the rotor are deduced from the cranking model. The method is described and results are presented concerning transition probabilities and energies in the high-spin regime for several rotational bands in Pb-199. The possible termination of the rotational bands is also discussed.
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| 14. |
- Carlsson, Gillis
(författare)
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Models for Rotating Nuclei - Cranking and Rotor + Particles Coupling
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation investigates properties of rotating atomic nuclei. Studies are performed using the cranking model and in the particles + rotor model. Properties studied are energy spectra and electromagnetic transition probabilities. The thesis also investigates the use of different liquid drop models at high spin values and studies the use of the particle + rotor approximation for the description of different 'exotic' ways of rotating. The dissertation comprises six original papers, which are presented following an introduction to the fields of research and the methods used and the systems studied. Paper I investigates the use of different meanfield parameters for the description of experimental high-spin states in 86Nb. A better agreement with experimental data could be found, however some experimental features proved hard to explain. In Paper II new experimental data on high-spin states in 58Ni was presented and compared with cranking calculations. A good agreement with calculation led to a clear interpretation of all observed states. The interaction and transitions between two of the rotational bands are analyzed and found to be sensitive to the deformation of the nucleus. In Paper III the average pairing energy is removed from the parameters of the liquid-drop model by performing a refitt to nuclear groundstate masses. The modified model is then used to calculate the total energy of the nucleus at high-spin values. Two different models are compared and one is found to be more reliable for light nuclei. In Paper IV the usual particle plus rotor model is extended to incorporate an arbitrary number of particles coupled to the rotor. This model is then used to describe the so called shears bands where states are formed by the coupling of perpendicular neutron and proton spin vectors. The same model is employed in Paper V for the description of collective wobbling excitations in nuclei. In Paper VI, new experimental data on quadrupole transitions in 142Gd are presented. These data are compared to the result of cranking calculations employing a monopole pairing interaction. Based on the calculations the relatively small transition probabilities are interpreted as being the result of the rotation taking place around the longest principal axis of the mass distribution.
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| 15. |
- Carlsson, Gillis, et al.
(författare)
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Nuclear binding energy at high spin
- 2006
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 831, s. 60-64
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Konferensbidrag (refereegranskat)abstract
- A method to calculate absolute values of the total nuclear binding energy in the high-spin regime is briefly described. Applications to test the position of specific orbitals are examplified on Z = 36 Kr isotopes with N = 36 - 38. Calculated binding energies of possible configurations for one dipole band in 199Pb are compared with experiment
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| 16. |
- Carlsson, Gillis, et al.
(författare)
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Nuclear shell structure and rotational bands in Nb-86
- 2004
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:2
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Tidskriftsartikel (refereegranskat)abstract
- The high spin structures in Nb-86 are analyzed using the cranked Nilsson-Strutinsky model. Energy versus spin curves as well as deformations and electric transition quadrupole moments are considered. It is concluded that different single-particle parameters compared with the standard values lead to better agreement with recent experimental results.
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| 17. |
- Carlsson, Gillis
(författare)
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Structure of wobbling excitations in Lu-163
- 2007
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 16:2, s. 634-642
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Tidskriftsartikel (refereegranskat)abstract
- Using a many-particles plus rotor model, wobbling excitations built on top of a triaxial superdeformed band in Lu-163 are investigated. By extracting all parameters for the rotor from a mean field calculation a good correspondence with calculations based on the random-phase approximation is achieved.
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| 18. |
- 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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| 19. |
- 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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| 20. |
- Gellanki, Jnaneswari, et al.
(författare)
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Comparative Study of Rotational Bands in the A~60 Mass Region: Modification of Nilsson Parameters
- 2014
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:2
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Tidskriftsartikel (refereegranskat)abstract
- The large number of high-spin bands that have been observed in A=56-62 nuclei are analyzed systematically within the cranked Nilsson-Strutinsky approach. Optimized Nilsson single-particle parameters are derived from investigations of energy differences between experimental and calculated rotational bands. Specifically, the relative energies of bands in neighboring nuclei whose configurations differ by having a high-j orbital either filled or empty are analyzed. The level schemes calculated with the new Nilsson parameters are compared with those using standard Nilsson parameters. Some configuration assignments are revised.
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| 21. |
- Kardan, Azam, et al.
(författare)
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Interpretation of normal-deformed bands in Lu 167
- 2020
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Ingår i: Physical Review C. - 2469-9985. ; 101:1
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Tidskriftsartikel (refereegranskat)abstract
- With the aim to get a general understanding of rotational bands in the deformed rare-earth region or in deformed nuclei in general, the observed normal-deformed rotational structures in Lu167 are interpreted within the unpaired and paired cranked Nilsson-Strutinsky formalisms, cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov. Particular attention is devoted to the band crossings. For this nucleus with the Fermi surface high up in the h11/2 shell, we conclude that except for the paired AB and BC crossings in configurations with an even and odd number of i13/2 neutrons, respectively, the observed band crossings can be understood within the unpaired formalism. Especially, it means that above the AB and BC crossings, the evolution with spin is described as a gradual alignment of the spin vectors of the particles outside closed shells. Consequently, the configurations can be characterized by the number of particles occupying open j shells or groups of j shells. In the present study, we revise the interpretation of some experimental bands and also the nature of the crossings while some previous configuration assignments are confirmed.
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| 22. |
- Lantz, Victor, et al.
(författare)
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Deep learning for inverse problems in quantum mechanics
- 2021
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Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 121:9
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Tidskriftsartikel (refereegranskat)abstract
- Inverse problems are important in quantum mechanics and involve such questions as finding which potential give a certain spectrum or which arrangement of atoms give certain properties to a molecule or solid. Inverse problems are typically very hard to solve and tend to be very compute intense. We here show that neural networks can easily solve inverse problems in quantum mechanics. It is known that a neural network can compute the spectrum of a given potential, a result which we reproduce. We find that the (much harder) inverse problem of computing the correct potential that gives a prescribed spectrum is equally easy for a neural network. We extend previous work where neural networks were used to find the electronic many-particle density given a potential by considering the inverse problem. That is, we show that neural networks can compute the potential that gives a prescribed many-electron density.
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| 23. |
- Ma, Hai-Liang, et al.
(författare)
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Interpretation of the high spin states in Lu-161: A paired and unpaired study
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:1
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Tidskriftsartikel (refereegranskat)abstract
- A paired cranked Nilsson-Strutinsky-Bogoliubov (CNSB) model is presented, which employs the same method to calculate the liquid-drop energy and moment of inertia as the unpaired cranked Nilsson-Strutinsky (CNS) model. In the CNSB model, the energy minimization is carried out in the mesh of pairing gaps Delta and Fermi levels lambda as well as deformation parameters. The high spin states in Lu-161 are then investigated with the CNSB and CNS models. The terminating structure shows a striking similarity with these two models. Combining the CNSB and CNS models, a complete understanding of high spin structures, including the normal deformed (ND) and triaxial strongly deformed (TSD) bands and observed side bands in Lu-161, is achieved. It appears that the only important paired crossings are the first i(13/2) neutron crossing and the first h(11/2) proton crossing. For the description of the unpaired high spin crossings, it is important to be able to distinguish between the pseudospin partners in the proton N = 4 shell, (d(5/2), g(7/2)) and (d(3/2), s(1/2)). The yrast bands are predicted to terminate, which explains the structure of a TSD-like band X2. A band crossing at I approximate to 36.5 for the TSD band in Lu-161, unique within the chain of even-N Lu isotopes, is well described by the CNSB model.
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| 24. |
- Masiteng, P. L., et al.
(författare)
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Close near-degeneracy in a pair of four-quasiparticle bands in Tl-194
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 83-88
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Tidskriftsartikel (refereegranskat)abstract
- A pair of rotational bands associated with the pi h(9/2) circle times nu i(13/2)(-1) configuration at lower spins and with the pi h(9/2) circle times nu i(13/2)(-3) configuration at higher spins is found in Tl-194. The two 4-quasiparticle bands show exceptionally close near-degeneracy in the excitation energies. Furthermore close similarity is also found in their alignments and B(M1)/B(E2) reduced transition probability ratios. Such close near-degeneracy probably indicates chiral geometry in the angular momentum space. (c) 2013 Elsevier B.V. All rights reserved.
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| 25. |
- Moeller, P., et al.
(författare)
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Axial and reflection asymmetry of the nuclear ground state
- 2008
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Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier BV. - 0092-640X. ; 94:5, s. 758-780
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Tidskriftsartikel (refereegranskat)abstract
- More than a decade ago we published a calculation of nuclear ground-state masses and deformations in Atomic Data and Nuclear Data Tables [P. Moller, J.R. Nix, W.D. Myers, W.J. Swiatecki, At. Data Nucl. Data Tables 59 (1995) 185]. In this study, triaxial nuclear shapes were not considered. We have now enhanced our model and studied the influence of triaxial shape degrees of freedom on the nuclear ground-state potential-energy (mass) and ground-state shape. It turns out that a few hundred nuclei are affected to a varying degree with the largest effect, about 0.7 MeV, occurring near Ru-108. We provide here a table of the calculated effects of triaxial shape degrees of freedom. Although axial-asymmetry effects were not considered in the 1995 mass calculation, it did study the effects of reflection-asymmetric shape degrees of freedom (epsilon(3)) on nuclear masses. However, the magnitude of the effect was not tabulated. Here, we provide such a table. In addition we calculate the effect in a much improved fashion: we search a four-dimensional deformation space (epsilon(2), epsilon(3), epsilon(4), and epsilon(6)). This is now possible because the computational resources available to us today are more than 100,000 times better than at the time we calculated the mass table published in 1995. (C) 2008 Elsevier Inc. All rights reserved.
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