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1.
  • Alexander, T., et al. (author)
  • Isomeric Ratios in 206Hg
  • 2015
  • In: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 46:3, s. 601-605
  • Journal article (peer-reviewed)abstract
    • Hg-206 was populated in the fragmentation of an E/A = 1 GeV Pb-208 beam at GSI. It was part of a campaign to study nuclei around Pb-208 via relativistic Coulomb excitation. The observation of the known isomeric states confirmed the identification of the fragmentation products. The isomeric decays were also used to prove that the correlations between beam identification detectors and the AGATA gamma-ray tracking array worked properly and that the tracking efficiency was independent of the time relative to the prompt flash.
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2.
  • Algora, A., et al. (author)
  • Pronounced Shape Change Induced by Quasiparticle Alignment
  • 2000
  • In: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 61:3
  • Journal article (peer-reviewed)abstract
    • Mean lifetimes of high-spin states of Kr-74 have been determined using the Doppler-shift attenuation method. The high-spin states were studied using the Ca-40(Ca-40, alpha 2p) reaction at a beam energy of 160 MeV with the GASP gamma-ray spectrometer. The ground-state band and negative parity side band show the presence of three different configurations in terms of transitional quadrupole deformations. A dramatic shape change was found along the ground-state band after the S-band crossing. The deduced quadrupole deformation changes are well reproduced by cranked Woods-Saxon Strutinsky calculations.
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3.
  • Andersson, Lise-Lotte, et al. (author)
  • Classification of Superdeformed Bands in the Mass A~60 Region
  • 2008
  • In: Nuclear Physics and Astrophysics. - : AIP. - 9780735406032 ; 1072, s. 211-214
  • Conference paper (peer-reviewed)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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4.
  • Andersson, Lise-Lotte, et al. (author)
  • Comprehensive Gamma-ray Spectroscopy of Rotational Bands in the N=Z+1 Nucleus 61Zn
  • 2009
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:2
  • Journal article (peer-reviewed)abstract
    • The Zn-61(30)31 nucleus has been studied via the combined data of two fusion-evaporation reaction experiments using a Ar-36 beam and a Si-28 target foil. The experimental setups involved the Ge array GAMMASPHERE and neutron and charged particle detectors placed around the target position. The resulting level scheme comprises about 120 excited states connected via some 180 gamma-ray transitions. In total, seven rotational structures were identified up to I similar to 25 or higher and compared with predictions from cranked Nilsson-Strutinsky calculations.
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5.
  • Andersson, Lise-Lotte, et al. (author)
  • Extensive Gamma-ray Spectroscopy of Normally and Superdeformed Structures in 61Cu
  • 2008
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 36:3, s. 251-278
  • Journal article (peer-reviewed)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.
  • Andersson, Lise-Lotte, et al. (author)
  • Gamma-ray Spectroscopy of Excited States in 61Zn
  • 2006
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 30:2, s. 381-390
  • Journal article (peer-reviewed)abstract
    • The Zn-61(30)31 isotope has been produced at the Oak Ridge National Laboratory in the fusion-evaporation reaction Ca-40(Mg-24, 2pn)Zn-61 at 104 MeV. The experimental set-up allowed gamma-rays to be detected in the CLARION Ge detector array in coincidence with the detection of recoiling nuclei in the focal plane at the end of the recoil mass spectrometer. This provides a unique identification of gamma-rays belonging to Zn-61. The excited states have been explored by means of recoil-gamma gamma coincidences, and the resulting decay scheme comprises almost 70 transitions. The data reveal numerous non-yrast states and suggest a revised spin and parity assignment for a previously observed superdeformed band. The resulting decay scheme is compared to predictions from different sets of large-scale shell model calculations.
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7.
  • Andersson, Lise-Lotte, et al. (author)
  • Identification of Excited States in 61Ga: Mirror Nuclei in the Upper fp Shell
  • 2005
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:1
  • Journal article (peer-reviewed)abstract
    • In the fusion-evaporation reaction Ca-40+Mg-24 at 104 MeV beam energy, excited states have been observed for the first time in the isotope Ga-31(61)30. The experimental setup comprised the Ge array CLARION, a recoil mass spectrometer and, in its focal plane, an ionization chamber. Five transitions in Ga-61 are identified, out of which a cascade of three transitions has been established by means of recoil-gammagamma coincidences. The strong transitions at 271 keV in Ga-61 and 124 keV in Zn-61 are viewed as the "mirror" 5/2(-)-->3/2(-) ground-state transitions. The rather large energy difference of 150 keV is suggested to arise from Coulomb monopole contributions. Shell-model calculations support this interpretation.
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8.
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9.
  • Andersson, T., et al. (author)
  • High-spin States in the A=39 Mirror Nuclei 39Ca and 39K
  • 1999
  • In: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 6, s. 5-8
  • Journal article (peer-reviewed)abstract
    • High-spin states of the mass A = 39 mirror pair K-39 and Ca-39 were investigated via the fusion-evaporation reaction Si-28+O-16 at 125 MeV beam energy. The GAMMASPHERE array in conjunction with the 4 pi charged-particle detector array MICROBALL and neutron detectors was used to detect gamma rays in coincidence with evaporated light particles. The results of the first high-spin study of the T-z = -1/2 nucleus Ca-39 are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d(3/2)-1f(7/2) configuration space.
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10.
  • Andreoiu, Corina, et al. (author)
  • Competing Decay-out Mechanisms of the Yrast Superdeformed Band in 59Cu
  • 2004
  • In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 701, s. 289-294
  • Conference paper (peer-reviewed)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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11.
  • Andreoiu, Corina, et al. (author)
  • Doorway States in the Gamma Decay-out of the Yrast Superdeformed Band in 59Cu
  • 2003
  • In: Physical Review Letters. - 1079-7114. ; 91:23
  • Journal article (peer-reviewed)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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12.
  • Andreoiu, Corina, et al. (author)
  • Evolution of Shapes in 59Cu
  • 2002
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 14:3, s. 317-348
  • Journal article (peer-reviewed)abstract
    • High-spin states in Cu-59 were populated using the fusion-evaporation reaction Si-28 + Ca-40 at a beam energy of 122 MeV. The Gammasphere Ge-detector array in conjunction with the 4pi charged-particle detector array Microball allowed for the detection of gamma-rays in coincidence with evaporated light particles. The resulting extensive high-spin decay scheme of Cu-59 is presented, which comprises more than 320 gamma-ray transitions connecting about 150 excited states. Their spins and parities have been assigned via directional correlations of gamma-rays emitted from oriented states. Average quadrupole moments of rotational bands have been determined from the analysis of residual Doppler shifts. Shell model calculations in the fp shell are invoked to study some of the low-spin states, while the experimental characteristics of the rotational bands are analyzed in the configuration-dependent cranked Nilsson-Strutinsky (CNS) approach.
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13.
  • Andreoiu, Corina, et al. (author)
  • First Identification of Excited States in 59Zn
  • 2002
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 15, s. 459-462
  • Journal article (peer-reviewed)abstract
    • Excited states in 59Zn were observed for the first time following the fusion-evaporation reaction 24Mg + 40Ca at a beam energy of 60 MeV. The GASP array in conjunction with the ISIS Silicon ball and the NeutronRing allowed for the detection of n-rays in coincidence with evaporated light particles. The mirror symmetry of 59Zn and 59Cu is discussed.
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14.
  • Andreoiu, Corina, et al. (author)
  • Yrast Superdeformed Band in 59Cu
  • 2000
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 62:5, s. 513011-513015
  • Journal article (peer-reviewed)abstract
    • High-spin states in 59Cu were populated using the fusion-evaporation reactions 28Si+40Ca at a beam energy of 125 MeV and 36Ar+28Si at a beam energy of 143 MeV. The Gammasphere array in conjunction with ancillary detector systems allowed for the identification of a superdeformed rotational band in 59Cu, which was firmly linked to low-spin yrast states. Using directional correlations of oriented states, a spin-parity assignment of Iπ = 25/2+ to the band head was possible. The average quadrupole moment of the band is measured to be Qt = (2.24±0.40) e b. The characteristics of the band are compared to neighboring nuclei and predictions of different mean-field theories.
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15.
  • Atanasova, L., et al. (author)
  • g-factor Measurements at RISING: The Cases of 127Sn and 128Sn
  • 2010
  • In: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 91:4
  • Journal article (peer-reviewed)abstract
    • We report on g-factor measurements of the 19/2(+) T-1/2 = 4.5(3) mu s isomer in Sn-127 and the 10(+) T-1/2 = 2.69(23) mu s isomer in Sn-128. These isomers were produced and spin-aligned in relativistic heavy-ion fragmentation at GSI and were selected and separated by the GSI fragment separator ( FRS). The gamma-rays of the isomeric decay were detected by the RISING gamma-ray spectrometer. The method of time-differential perturbed angular distributions was utilized. The measured g-factors, g(19/2(+); Sn-127) =-0.17(2) and g(10(+); Sn-128)=-0.20(4), are compared with shell model calculations. The measured g-factors confirm the predominantly nu h(11/2)(-2) and nu(s(1/2)(-1) h(11/2)(-2)) character of the 10(+) and 19/2(-) isomers in Sn-128 and Sn-127, respectively. The results demonstrate the feasibility of the method for similar measurements in exotic neutron-rich nuclei. Copyright (C) EPLA, 2010
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16.
  • Banu, A, et al. (author)
  • 108Sn Studied with Intermediate-energy Coulomb Excitation
  • 2005
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:6
  • Journal article (peer-reviewed)abstract
    • The unstable neutron-deficient Sn-108 isotope has been studied in inverse kinematics by intermediate-energy Coulomb excitation using the RISING/FRS experimental setup at GSI. This is the highest Z nucleus studied so far with this method. Its reduced transition probability B (E2;0(g.s.)(+)-> 2(1)(+)) has been measured for the first time. The extracted B(E2) value of 0.230(57)e(2) b(2) has been determined relative to the known value in the stable Sn-112 isotope. The result is discussed in the framework of recent large-scale shell model calculations performed with realistic effective interactions. The roles of particle-hole excitations of the Sn-100 core and of the Z=50 shell gap for the E2 polarization are investigated.
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17.
  • Becker, F, et al. (author)
  • Status of the RISING Project at GSI
  • 2005
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 25:Suppl 1, s. 719-722
  • Journal article (peer-reviewed)abstract
    • The FRS-RISING set-up at GSI uses secondary radioactive beams at relativistic energies for nuclear structure studies. At GSI the fragmentation or fission of stable primary beams up to U-238 provide secondary beams with sufficient intensity to perform gamma-ray spectroscopy. The RISING set-up is described and results of the first RISING campaign are presented. New experimental methods at relativistic energies are being investigated. Future experiments focus on state-of-the art nuclear structure physics covering exotic nuclei all over the nuclear chart.
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18.
  • Bednarczyk, P, et al. (author)
  • Status of the RISING Project at Relativistic Energies
  • 2005
  • In: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 36:4, s. 1235-1244
  • Journal article (peer-reviewed)abstract
    • The RISING project was designed to perform high-resolution gamma-ray spectroscopy with radioactive beams at GSI. Unstable beams were produced by fragmentation of relativistic heavy ion projectiles provided by the SIS synchrotron. The fragment separator FRS was used to select and to focus the exotic fragments at about 100A MeV energy on a secondary target. Various charged particle detectors enabled an event-by-event tracking of the incoming radioactive projectiles and the reaction products, thus allowing for a selection of the nuclei of interest and their velocity vector reconstruction. The gamma-ray detection system consisting of the EUROBALL Cluster Ge detectors and the large volume HECTOR BaF2 detectors measured prompt gamma-radiation from nuclei excited in the secondary target. Despite the huge Doppler shift due to the high recoil velocity (beta approximate to 40%), RISING achieved a gamma-energy resolution below 2%. The paper reviews the present status of the RISING project.
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19.
  • Berry, Tom A., et al. (author)
  • Investigation of the Δn = 0 selection rule in Gamow-Teller transitions: The β-decay of 207 Hg
  • 2019
  • In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 793, s. 271-275
  • Journal article (peer-reviewed)abstract
    • Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn=0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N>82) and Z=82 (for N>126). The level of forbiddenness of the Δn=1ν1g 9/2 →π0g 7/2 transition has been investigated from the β − decay of the ground state of 207 Hg into the single-proton-hole nucleus 207 Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g 7/2 −1 state in 207 Tl, an upper limit of 3.9×10 −3 % was obtained for the probability of this decay, corresponding to log⁡ft>8.8 within a 95% confidence limit. This is the most stringent test of the Δn=0 selection rule to date. © 2019 The Authors
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20.
  • Blazhev, A., et al. (author)
  • Observation of a core-excited E4 isomer in Cd-98
  • 2004
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69
  • Journal article (peer-reviewed)abstract
    • A core-excited I-pi=(12(+)) spin-gap isomer was identified in Cd-98 in an experiment at EUROBALL IV. It was found to feed the known I-pi=(8(+)) seniority isomer by an E4 transition. Half-lives of T-1/2=0.23 ((+4)(-3)) mus and 0.17 ((+6)(-4)) mus were measured for the two states at E-x=6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a Sn-100 shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, Sn-100 core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltae(pi)
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21.
  • Carroll, R.J., et al. (author)
  • Competition between Allowed and First-Forbidden β Decay: The Case of Hg 208 → Tl 208
  • 2020
  • In: Physical Review Letters. - 1079-7114. ; 125:19
  • Journal article (peer-reviewed)abstract
    • The β decay of Hg208 into the one-proton hole, one neutron-particle Tl81208127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z
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22.
  • Cederkäll, Joakim, et al. (author)
  • Sub-Barrier Coulomb Excitation of ^110Sn and Its Implications for the ^100Sn Shell Closure
  • 2007
  • In: Physical Review Letters. - 1079-7114. ; 98:17, s. 172501-
  • Journal article (peer-reviewed)abstract
    • The first excited 2+ state of the unstable isotope 110Sn has been studied in safe Coulomb excitation at 2.82 MeV/u using the MINIBALL array at the REX-ISOLDE post accelerator at CERN. This is the first measurement of the reduced transition probability of this state using this method for a neutron deficient Sn isotope. The strength of the approach lies in the excellent peak-to-background ratio that is achieved. The extracted reduced transition probability, B(E2:0+-->2+)=0.220±0.022e2b2, strengthens the observation of the evolution of the B(E2) values of neutron deficient Sn isotopes that was observed recently in intermediate-energy Coulomb excitation of 108Sn. It implies that the trend of these reduced transition probabilities in the even-even Sn isotopes is not symmetric with respect to the midshell mass number A=116 as 100Sn is approached.
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23.
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24.
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25.
  • DiJulio, Douglas, et al. (author)
  • Coulomb excitation of In-107
  • 2013
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:1
  • Journal article (peer-reviewed)abstract
    • The radioactive isotope In-107 was studied using sub-barrier Coulomb excitation at the REX-ISOLDE facility at CERN. Two gamma rays were observed during the experiment, corresponding to the low-lying 11/2(+) and 3/2(-)states. The reduced transition probability of the 11/2(+) state was determined with the semiclassical Coulomb excitation code GOSIA2. The result is discussed in comparison to large-scale shell-model calculations, previous unified-model calculations, and earlier Coulomb excitation measurements in the odd-mass In isotopes. DOI: 10.1103/PhysRevC.87.017301
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26.
  • DiJulio, Douglas, et al. (author)
  • Coulomb excitation of Sn-107
  • 2012
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 48:7
  • Journal article (peer-reviewed)abstract
    • The radioactive isotope Sn-107 was studied using Coulomb excitation at the REX-ISOLDE facility at CERN. This is the lightest odd-Sn nucleus examined using this technique. The reduced transition probability of the lowest-lying 3/2(+) state was measured and is compared to shell-model predictions based on several sets of single-neutron energies relative to Sn-100. Similar to the transition probabilities for the 2(+) states in the neutron-deficient even-even Sn nuclei, the measured value is underestimated by shell-model calculations. Part of the strength may be recovered by considering the ordering of the d(5/2) and g(7/2) single-neutron states.
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27.
  • DiJulio, Douglas, et al. (author)
  • Electromagnetic properties of vibrational bands in Er-170
  • 2011
  • In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 47:2, s. 25-
  • Journal article (peer-reviewed)abstract
    • Excited states of the nucleus Er-170 have been studied by Coulomb excitation using the GASP gamma-ray detector system at the Laboratori Nazionali di Legnaro. The ground-state band along with a low-lying K-pi = 0(+) band and gamma-vibrational band were populated during the experiment. Based on the measured gamma-ray yields, a set of interband and intraband matrix elements has been extracted using the Coulomb excitation code GOSIA. The resulting E2 matrix elements are compared to collective model predictions.
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28.
  • DiJulio, Douglas, et al. (author)
  • Excitation strengths in Sn-109: Single-neutron and collective excitations near Sn-100
  • 2012
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 86:3
  • Journal article (peer-reviewed)abstract
    • A set of B(E2) values for the low-lying excited states in the radioactive isotope Sn-109 were deduced from a Coulomb excitation experiment. The 2.87-MeV/u radioactive beam was produced at the REX-ISOLDE facility at CERN and was incident on a secondary Ni-58 target. The B(E2) values were determined using the known 2(+) -> 0(+) reduced transition probability in Ni-58 as normalization with the semiclassical Coulomb excitation code GOSIA2. The transition probabilities are compared to shell-model calculations based on a realistic nucleon-nucleon interaction and the predictions of a simple core-excitation model. This measurement represents the first determination of multiple B(E2) values in a light Sn nucleus using the Coulomb excitation technique with low-energy radioactive beams. The results provide constraints for the single-neutron states relative to Sn-100 and also indicate the importance of both single-neutron and collective excitations in the light Sn isotopes.
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29.
  • DiJulio, Douglas, et al. (author)
  • Shell model based Coulomb excitation gamma-ray intensity calculations in Sn-107
  • 2012
  • In: Physica Scripta. - 0031-8949. ; T150
  • Journal article (peer-reviewed)abstract
    • In this work, we present recent shell model calculations, based on a realistic nucleon-nucleon interaction, for the light Sn-107,Sn-109 nuclei. By combining the calculations with the semi-classical Coulomb excitation code GOSIA, a set of gamma-ray intensities has been generated. The calculated intensities are compared with the data from recent Coulomb excitation studies in inverse kinematics at the REX-ISOLDE facility with the nucleus Sn-107. The results are discussed in the context of the ordering of the single-particle orbits relative to Sn-100.
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30.
  • DiJulio, Douglas, et al. (author)
  • Sub-barrier Coulomb excitation of Sn-107
  • 2012
  • In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 381, s. 012073-012073
  • Conference paper (peer-reviewed)abstract
    • A Coulomb excitation experiment in inverse kinematics has been carried out at the REX-ISOLDE facility in order to study the properties of low-lying excited states in Sn-107. The measured gamma ray spectrum has been compared with predicted gamma ray spectra from a combined shell-model and GOSIA analysis. In this approach, a set of matrix elements, generated within the shell-model framework, based on a realistic nucleon-nucleon interaction and a set of single-particle energies relative to Sn-100, is used as input. Comparison between the calculated and predicted spectra can be used to help identify the placement of the single-neutron states in Sn-101. In particular, the results can potentially provide clues on the ordering of the two lowest-lying orbits; the g(7/2) and d(5/2) states.
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31.
  • 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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32.
  • du Rietz, Rickard, et al. (author)
  • Effective Charges in the fp Shell
  • 2004
  • In: Physical Review Letters. - 1079-7114. ; 93:22
  • Journal article (peer-reviewed)abstract
    • Following the heavy-ion fusion-evaporation reaction S-32+Mg-24 at 95 MeV beam energy the lifetimes of analogue states in the T-z=+/-1/2 A=51 mirror nuclei Fe-51 and Mn-51 have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p)similar to1.15e and epsilon(n)similar to0.80e.
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33.
  • du Rietz, Rickard, et al. (author)
  • Investigation of High-spin States in 53Fe
  • 2005
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:1
  • Journal article (peer-reviewed)abstract
    • The fusion-evaporation reactions Si-28(S-32,1 alpha 2p1n)Fe-53 at 125 MeV and Mg-24(S-32,2p1n)Fe-53 at a 95-MeV beam energy were used to investigate excited states in Fe-53. The combination of the Gammasphere Ge detector array and ancillary devices led to the construction of an extensive level scheme comprising some 90 transitions connecting 40 states. The lifetime of the yrast 25/2(-) state and upper limits for the lifetimes of a number of additional states were determined using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The experimental results are compared to large-scale shell-model calculations using different sets of two-body matrix elements. In particular, predictions on electromagnetic decay properties such as lifetimes, branching ratios, and mixing ratios are studied in detail.
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34.
  • Ekman, Jörgen, et al. (author)
  • Core Excited States in the A=51 Mirror Nuclei
  • 2004
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:5
  • Journal article (peer-reviewed)abstract
    • Three previously unknown high-energy gamma-ray transitions between 4.2 and 5.4 MeV were identified in the T-z=-1/2 nucleus Fe-51 following the fusion-evaporation reaction S-32(Si-28, 2alpha1n)Fe-51. These transitions represent decays of core excited states. The gamma rays were detected in the Ge detector array Gammasphere combined with the neutron detector system Neutron Shell and the charged-particle array Microball. The three transitions are related to the mirror transitions in the T-z= + 1 /2 nucleus Mn-51, and the resulting mirror-energy difference diagram is discussed with predictions from large-scale shell-model calculations.
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35.
  • Ekman, Jörgen, et al. (author)
  • Evidence for a 1g9/2 Rotational Band in 51Mn
  • 2002
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 66:5, s. 513011-513015
  • Journal article (peer-reviewed)abstract
    • A terminating rotational band has been identified in Mn-51 following the Si-28(S-32,2alpha1p)Mn-51 fusion-evaporation reaction at 130 MeV beam energy. Spins and tentative positive parities of the band members are assigned based on angular distribution and correlation measurements of transitions, which connect the rotational structure with previously known yrast states. Configuration-dependent cranked Nilsson-Strutinsky calculations suggest a configuration of the band, which comprises one particle in the 1g(9/2) intruder orbit.
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36.
  • Ekman, Jörgen, et al. (author)
  • Gamma-ray Spectroscopy of Core-excited States in 51Mn
  • 2004
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:1
  • Journal article (peer-reviewed)abstract
    • The level scheme of Mn-51 has been investigated using the Si-28(S-32 2alpha1p)Mn-51 fusion-evaporation reaction at 125 MeV beam energy. The gamma rays were detected in the Ge-detector array Gammasphere, which was coupled to the 4pi-charged-particle detector Microball and the Neutron Shell for the coincident detection of evaporated particles. Over 100 new gamma-ray transitions connecting some 50 excited states have been identified. Most of the states are built on particle-hole excitations across the shell gaps at particle number N=Z=28. The rich experimental data allows for a 'comprehensive comparison of core-excited states with results from large-scale shell-model calculations, which are known to provide excellent predictions for the lower-lying yrast and near-yrast levels in 1f(7/2) nuclei.
  •  
37.
  • Ekman, Jörgen, et al. (author)
  • Mirror Symmetry in the Upper fp Shell
  • 2005
  • In: Modern Physics Letters A. - : World Scientific Publishing. - 0217-7323 .- 1793-6632. ; 20:39, s. 2977-2992
  • Research review (peer-reviewed)abstract
    • A detailed investigation of the contribution from Coulomb effects to the observed mirror energy difference diagrams in nuclei in the lower part of the upper fp shell is presented by means of large-scale shell-model calculations.
  •  
38.
  • Ekman, Jörgen, et al. (author)
  • News on Mirror Nuclei in the sd and fp Shells
  • 2005
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 25:Suppl 1, s. 363-366
  • Journal article (peer-reviewed)abstract
    • Novel experimental results on mirror nuclei in the sd and fp shells are presented. Their respective Mirror Energy Difference (MED) diagrams are interpreted by means of large-scale shell-model calculations. A unique way of extracting effective charges from isospin symmetry studies is also discussed.
  •  
39.
  • Ekman, Jörgen, et al. (author)
  • The A=51 Mirror Nuclei 51Fe and 51Mn
  • 2000
  • In: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 9, s. 13-17
  • Journal article (peer-reviewed)abstract
    • Eighteen previously unknown gamma -ray transitions were identified in the T-z = -1/2 nucleus Fe-51 following the fusion-evaporation reaction S-32(Si-28,2 alpha 1n)Fe-51. The lever scheme reaches the fully aligned I-pi = 27/2(-) terminating state of the five holes in the f(7/2) shell. The 17/2(-) state was found to be isomeric, and the lifetime was measured to be 2.87 ns. The mirror symmetry of Fe-51 and Mn-51 is discussed, and the level scheme of Fe-51 is compared to shell-model calculations.
  •  
40.
  • Ekman, Jörgen, et al. (author)
  • Unusual Isospin-Breaking and Isospin-mixing Effects in the A=35 Mirror Nuclei
  • 2004
  • In: Physical Review Letters. - 1079-7114. ; 92:13
  • Journal article (peer-reviewed)abstract
    • Excited states have been studied in Ar-35 following the O-16(Mg-24,1alpha1n)Ar-35 fusion-evaporation reaction at 60 MeV using the Ge-detector array GASP. A comparison with the mirror nucleus Cl-35 shows two remarkable features: (i) A surprisingly large energy difference for the 13/2(-) states, in which the hitherto overlooked electromagnetic spin-orbit term is shown to play a major role, and (ii) a very different decay pattern for the 7/2(-) states, which provides direct evidence of isospin mixing.
  •  
41.
  • Ekström, Andreas, et al. (author)
  • 0(gs)+ -->2(1)+ transition strengths in 106Sn and 108Sn.
  • 2008
  • In: Physical Review Letters. - 1079-7114. ; 101:1
  • Journal article (peer-reviewed)abstract
    • The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.
  •  
42.
  • Ekström, Andreas, et al. (author)
  • Coulomb excitation of Sn-110 using REX-ISOLDE
  • 2006
  • In: Physica Scripta. - 1402-4896 .- 0031-8949. ; T125, s. 190-191
  • Conference paper (peer-reviewed)abstract
    • In this paper, we report the preliminary result from the first Coulomb excitation experiment at REX-ISOLDE (Habs et al 1998 Nucl. Instrum. Methods B 139 128) using neutron-deficient Sn-beams. The motivation of the experiment is to deduce the reduced transition probability, B(E2; 2(+) -> 0(+)), for the sequence of neutron deficient, unstable, even-even Sn- isotopes from Sn-110 to ultimately Sn-110. Safe Coulomb excitation using a radioactive beam opens up a new path to study the lifetime of the first excited 2(+) state in these isotopes. The de-excitation path following fusion-evaporation reactions will for the even-even Sn isotopes pass via an isomeric 6(+) state, located at higher energy, which thus hampers measurements of the lifetime of the first excited state using, e. g., recoil-distance methods. For this reason the reduced transition probability of the first excited 2(+) state has remained unknown in this chain of isotopes although the B(E2) value of the stable isotope Sn-112 was measured approximately 30 years ago (see, e. g., Stelson et al 1970 Phys. Rev. C 2 2015). Our experiment is thus the first to accomplish a measurement of this quantity in Sn-110. It is believed that the determination of the B(E2) value in Sn-110 will indicate the turnover point from a trend of increasing B(E2) values for the heavier isotopes to a trend characterized by less collectivity. Our first preliminary result indicates that this assumption may well be correct.
  •  
43.
  • Ekström, Andreas, et al. (author)
  • Coulomb excitation of the odd-odd isotopes In-106,In-108
  • 2010
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 44:3, s. 355-361
  • Journal article (peer-reviewed)abstract
    • The low-lying states in the odd-odd and unstable isotopes In-106,In-108 have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN. With the additional data provided here the pi g(9/2)(-1) circle times nu d(5/2) and pi g(9/2)(-1) circle times nu g7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed gamma-ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction. The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the excitation pattern of the two isotopes. The calculations exclude a 6(+) ground state in In-106. This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results, it is also concluded that the ordering of the isomeric and ground state in In-108 is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367 keV in In-106 is also reported.
  •  
44.
  • Ekström, Andreas, et al. (author)
  • Determination of the isomeric fraction in a postaccelerated radioactive ion beam using the coupled decay-chain equations
  • 2010
  • In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 614:2, s. 303-307
  • Journal article (peer-reviewed)abstract
    • A method based on the coupled decay-chain equations for extracting the isotopic and the isomeric composition of a postaccelerated radioactive ion beam is presented and demonstrated on a data set from a Coulomb excitation experiment. This is the first attempt of analyzing the content of a postaccelerated radioactive ion beam using this technique. The beam composition is required for an absolute normalization of the measurement. The strength of the method, as compared to present online-based methods, lies in the determination of the isomeric fraction of a partially isomeric beam using all data accumulated during the experiment. We discuss the limitations and sensitivity of the method with respect to the gamma-ray detection efficiency and the accumulated flux. (C) 2010 Elsevier B.V. All rights reserved.
  •  
45.
  • Ekström, Andreas, et al. (author)
  • Electric quadrupole moments of the 2(1)(+) states in Cd-100,Cd-102,Cd-104
  • 2009
  • In: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
  • Journal article (peer-reviewed)abstract
    • Using the REX-ISOLDE facility at CERN the Coulomb excitation cross sections for the 0(gs)(+)-> 2(1)(+) transition in the beta-unstable isotopes Cd-100,Cd-102,Cd-104 have been measured for the first time. Two different targets were used, which allows for the first extraction of the static electric quadrupole moments Q(2(1)(+)) in Cd-102,Cd-104. In addition to the B(E2) values in Cd-102,Cd-104, a first experimental limit for the B(E2) value in Cd-100 is presented. The data was analyzed using the maximum likelihood method. The provided probability distributions impose a test for theoretical predictions of the static and dynamic moments. The data are interpreted within the shell-model using realistic matrix elements obtained from a G-matrix renormalized CD-Bonn interaction. In view of recent results for the light Sn isotopes the data are discussed in the context of a renormalization of the neutron effective charge. This study is the first to use the reorientation effect for post-accelerated short-lived radioactive isotopes to simultaneously determine the B(E2) and the Q(2(1)(+)) values.
  •  
46.
  • Ekström, Andreas, et al. (author)
  • Sub-barrier Coulomb excitation of Sn-106,Sn-108,Sn-110
  • 2008
  • In: Frontiers in Nuclear structure, Astrophysics and Reactions - Finustar 2, AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. ; 1012, s. 296-299
  • Conference paper (peer-reviewed)abstract
    • The reduced transition probabilities between the first excited 2(+) state and the 0(+) ground state, B(E2; 0(+) -> 2(+)), have been measured in Sn-106,Sn-108,Sn-110 using sub-barrier Coulomb excitation in inverse kinematics at REX-ISOLDE. The results are, B(E2;0(+) -> 2(+)) = 0.220(22),0.226(17), and 0.228(32) e(2)b(2), for Sn-110, Sn-108, and Sn-106, respectively. The results for Sn-106,Sn-108 are preliminary. De-excitation gamma-rays were detected by the MINIBALL Ge-array. The B(E2) reveals detailed information about the nuclear wave function. A shell model prediction based on an effective CD-Bonn interaction in the nu(0g(7/2),2s, 1d, 0h(11/2)) model space using e(eff)(nu) =1.0 e follows the experimental values for the neutron rich Sn isotopes, but fails to reproduce the results presented here.
  •  
47.
  •  
48.
  • Fahlander, Claes (author)
  • Discovery of Superheavy Elements
  • 2019
  • In: Nuclear Physics News. - : Informa UK Limited. - 1061-9127 .- 1931-7336. ; 29:1, s. 3-4
  • Journal article (other academic/artistic)
  •  
49.
  • Fahlander, Claes (author)
  • Engaging local industry in the development of basic research infrastructure and instrumentation - The case of HIE-ISOLDE and ESS Scandinavia
  • 2016
  • In: Latin American Symposium on Nuclear Physics and Applications, LASNPA 2015. - : Author(s). - 9780735414112 ; 1753
  • Conference paper (peer-reviewed)abstract
    • Two world-class research facilities, the European Spallation Source, ESS, and the light-source facility MAX-IV, are being built in southern Sweden. They will primarily, when completed, be used for research in the fields of material sciences, life sciences, medicine and pharmacology. Their construction and the operation and maintenance of them for many years will create new business opportunities for companies in Europe in general and in Sweden, Denmark and Norway in particular in many different sectors. A project, CATE, Cluster for Accelerator Technology, was set up with the aim to strengthen the skills of companies in the Öresund-Kattegat-Skagerrak region in Scandinavia in the field of accelerator technology such that they will become competitive and be able to take advantage of the potential of these two research facilities. CATE was strategically important and has helped to create partnerships between companies and new business opportunities in the region.
  •  
50.
  • Fahlander, Claes, et al. (author)
  • Evolution and Destruction of Shapes in 59Cu
  • 2002
  • In: Challenges of Nuclear Structure. Proceedings of the 7th International Spring Seminar on Nuclear Physics. - 9810247257 ; , s. 393-400
  • Conference paper (peer-reviewed)abstract
    • An extensive high-spin level scheme has been established in 59Cu using a heavy-ion fusion evaporation reaction and the GAMMASPHERE multidetector array in conjunction with MICROBALL. Next to the spherical states at low excitation energy a large number of regular sequences of high-energy γ-ray transitions have been observed, which form rotational bands with various degree of deformation. For the yrast superdeformed band about 90% of the intensity of the discrete γ decay-out, distributed over about 30 decay paths, is known, which allows for a detailed study of this decay-out process. Two of the deformed bands were found to decay by prompt proton emission into two different spherical states of 58Ni, in direct competition with the γ decay-out process
  •  
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