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1.
  • Reifarth, R., et al. (författare)
  • Nuclear astrophysics with radioactive ions at FAIR
  • 2016
  • Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
  • Konferensbidrag (refereegranskat)abstract
    • The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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2.
  • Antonov, A. N., et al. (författare)
  • The electron-ion scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR)-A conceptual design study
  • 2011
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087. ; 637:1, s. 60-76
  • Tidskriftsartikel (refereegranskat)abstract
    • The electron-ion scattering experiment ELISe is part of the installations envisaged at the new experimental storage ring at the International Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. It offers an unique opportunity to use electrons as probe in investigations of the structure of exotic nuclei. The conceptual design and the scientific challenges of ELISe are presented. (C) 2011 Elsevier B.V. All rights reserved.
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3.
  • Nilsson, Thomas, 1965, et al. (författare)
  • Neutron Momentum Distributions from Core Break-up Reactions of Halo Nuclei
  • 1995
  • Ingår i: Europhysics Letters. - 0295-5075 .- 1286-4854. ; 30:1, s. 19-24
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron angular distributions from violent break-up reactions of Li-11 and Be-11 have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles.
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4.
  • Aksyutina, Y., et al. (författare)
  • Study of the Be14 continuum: Identification and structure of its second 2+ state
  • 2013
  • Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:24, s. article nr. 242501-
  • Tidskriftsartikel (refereegranskat)abstract
    • The coupling between bound quantum states and those in the continuum is of high theoretical interest. Experimental studies of bound drip-line nuclei provide ideal testing grounds for such investigations since they, due to the feeble binding energy of their valence particles, are easy to excite into the continuum. In this Letter, continuum states in the heaviest particle-stable Be isotope, Be14, are studied by employing the method of inelastic proton scattering in inverse kinematics. New continuum states are found at excitation energies E*=3.54(16) MeV and E*=5.25(19) MeV. The structure of the earlier known 21+ state at 1.54(13) MeV was confirmed with a predominantly (0d5/2)2 configuration while there is very clear evidence that the 22+ state has a predominant (1s1/2, 0d 5/2) structure with a preferential three-body decay mechanism. The region at about 7 MeV excitation shows distinct features of sequential neutron decay via intermediate states in Be13. This demonstrates that the increasing availability of energetic beams of exotic nuclei opens up new vistas for experiments leading towards a new understanding of the interplay between bound and continuum states. © 2013 American Physical Society.
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5.
  • Humbert, F., et al. (författare)
  • Longitudinal and Transverse-Momentum Distributions of Li-9 Fragments from Break-up of Li-11
  • 1995
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 347:3-4, s. 198-204
  • Tidskriftsartikel (refereegranskat)abstract
    • Transverse and longitudinal momentum distributions of Li-9 fragments from Li-11 break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was measured to be sigma(-2n), = 0.26 +/- 0.02 b for the carbon target, sigma(-2n) = 0.47 +/- 0.08 b for the aluminum target and sigma(-2n), = 1.9 +/- 0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM approximate to 47 MeV/c) of the transverse and longitudinal momentum distributions of the Li-9 fragments. The physical implications of this are discussed.
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6.
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7.
  • Nilsson, Thomas, 1965, et al. (författare)
  • He-6 and neutron momentum distributions from He-8 in nuclear break-up reactions at 240 MeV/u
  • 1996
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 598:3, s. 418-434
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron and He-6 momentum distributions from He-8 break-up reactions in a C target have been measured at 240 MeV/u. The two-neutron removal cross section was found to be sigma(-2n) = 0.27 +/- 0.03 b. The nature of the momentum distributions is interpreted in some simple reaction scenarios.
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8.
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9.
  • Aksyutina, Y., et al. (författare)
  • Structure of the unbound nucleus Be-13: One-neutron knockout reaction data from Be-14 analyzed in a holistic approach
  • 2013
  • Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 87:6
  • Tidskriftsartikel (refereegranskat)abstract
    • At the ALADIN-LAND setup at GSI the unbound nucleus Be-13 has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of Be-14 ions impinging on a liquid hydrogen target. An analysis of the data including all available information about Be-13, and in particular recent data from a similar experiment performed at RIKEN, has been performed. A consistent description is reached. It is found that the excitation spectrum is dominated by s-waves at low energy, which solves problems from previous seemingly contradictory interpretations. A possible interference between two s-states in Be-13 is also discussed. The results indicate that the ground-state wave function of Be-14 is dominated by valence neutrons in the s-shell contributing with 60-75% of the total neutron knockout cross section.
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10.
  • Aleksandrov, D., et al. (författare)
  • Halo excitations in fragmentation of He-6 at 240 MeV/u on carbon and lead targets
  • 2000
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 669:1-2, s. 51-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissociation of a 240 MeV/u beam of He-6, incident on carbon and lead targets, has been studied in kinematically complete experiments to investigate low-lying excitation modes in the halo nucleus He-6. It is shown that alignment effects characterize the inelastic scattering and allow an unambiguous assignment of the spin of a narrow resonance observed in the excitation energy spectrum. The differential cross sections for the He-6 inelastic scattering on carbon and lead targets were deduced from the measured moments of the two neutrons and the a-particle. An analysis of these distributions shows that quadrupole and, possibly, monopole excitations characterize the hadronic interaction, while the dipole mode is dominating in Coulomb dissociation. Neither theoretically predicted new resonance states in He-6 nor nuclear excitation of a dipole mode were found. Direct evidence has been obtained for strong suppression of Coulornb post-acceleration in direct Coulomb breakup in a lead target.
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11.
  • Aleksandrov, D., et al. (författare)
  • Invariant mass spectrum and alpha-n correlation function studied in the fragmentation of He-6 on a carbon target
  • 1998
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 633:2, s. 234-246
  • Tidskriftsartikel (refereegranskat)abstract
    • Momentum distributions and invariant mass spectra from the breakup of He-6 ions with an energy of 240 MeV/u interacting with a carbon target have been studied. The data were used to extract information about the reaction mechanism which is influenced by the structure of He-6. It is found that the dominant reaction mechanism is a two-step process: knock out of one neutron followed by the decay of the He-5 resonance. The shape of the (alpha+n) two-body invariant mass spectrum is interpreted as mainly reflecting the 5He ground state which is a J(pi) = 3/2(-) resonance. However, no evidence for correlations between cu particles and neutrons is observed in the momentum widths of the distributions. It is demonstrated that a combined analysis of the two-body invariant mass spectrum and an appropriate correlation function may be used to determine the properties of the intermediate resonance. (C) 1998 Elsevier Science B.V.
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12.
  • Chulkov, L. V., et al. (författare)
  • Large spin alignment of the unbound He-5 fragment after fragmentation of 240 MeV/nucleon He-6
  • 1997
  • Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 79:2, s. 201-204
  • Tidskriftsartikel (refereegranskat)abstract
    • Peripheral fragmentation of a 240 MeV/nucleon beam of the halo nucleus He-6 incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus He-5 is the dominant fragmentation mechanism and that it leads to a spin alignment of He-5 in a plane perpendicular to the He-5 momentum vector. This is expected to be a common feature for all neutron halo nuclei.
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13.
  • Johansson, Håkan T, 1977, et al. (författare)
  • The unbound isotopes He-9,He-10
  • 2010
  • Ingår i: Nuclear Physics A. - Elsevier : Elsevier BV. - 0375-9474 .- 1873-1554. ; 842:1-4, s. 15-32
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound nuclei He-9 and He-10 have been produced in proton-knockout reactions from a 280 MeV/u Li-11 beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, He-8 + n and He-8 + 2n, employing reaction models incorporating the structure of Li-11. The (8H)e + n relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of -3.17(66) fm. This spectrum also shows evidence for resonance states at 1.33(8) MeV and at 2.4 MeV above the He-8 + n threshold. It is argued that the s-state might not be the He-9 ground state. For He-8 + n + n, the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at 1.42(10) MeV (Gamma = 1.11(76) MeV) superimposed on a correlated background, or two overlapping resonances, a ground state at 1.54(11) MeV (Gamma = 1.91(41) MeV) together with an excited state at 3.99(26) MeV (Gamma = 1.64(89) MeV). The two possible interpretations are discussed. (C) 2010 Elsevier B.V. All rights reserved.
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14.
  • Wollersheim, HJ, et al. (författare)
  • Rare ISotopes INvestigation at GSI (RISING) Using Gamma-ray Spectroscopy at Relativistic Energies
  • 2005
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 537:3, s. 637-657
  • Tidskriftsartikel (refereegranskat)abstract
    • The Rare ISotopes INvestigation at GSI project combines the former EUROBALL Ge-Cluster detectors, the MINIBALL Ge detectors, BaF2--HECTOR detectors, and the fragment separator at GSI for high-resolution in-beam gamma-ray spectroscopy measurements with radioactive beams. These secondary beams produced at relativistic energies are used for Coulomb excitation or secondary fragmentation experiments in order to explore the nuclear structure of the projectiles or projectile like nuclei by measuring de-excitation photons. The newly designed detector array is described and the performance characteristics are given. Moreover, particularities of the experimental technique are discussed.
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15.
  • Zinser, M., et al. (författare)
  • Invariant-mass spectroscopy of Li-10 and Li-11
  • 1997
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 619:1-2, s. 151-176
  • Tidskriftsartikel (refereegranskat)abstract
    • Break-up of secondary Li-11 ion beams (280 MeV/nucleon) on C and Pb targets into Li-9 and neutrons is studied experimentally. Cross sections and neutron multiplicity distributions are obtained, characterizing different reaction mechanisms. Invariant-mass spectroscopy for Li-11 and Li-10 is performed. The E1 strength distribution, deduced from electromagnetic excitation of Li-11 up to an excitation energy of 4 MeV comprises similar to 8% of the Thomas-Reiche-Kuhn energy-weighted sumrule strength. Two low-lying resonance-like structures are observed for Li-10 at decay energies of 0.21(5) and 0.62(10) MeV, the former one carrying 26(10)% of the strength and likely to be associated with an s-wave neutron decay. A strong di-neutron correlation in Li-11 can be discarded. Calculations in a quasi-particle RPA approach are compared with the experimental results for Li-10 and Li-11. (C) 1997 Elsevier Science B.V.
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16.
  • Aksyutina, Yu, et al. (författare)
  • Lithium isotopes beyond the drip line
  • 2008
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 666:5, s. 430-434
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound isotopes 10Li, 12Li and 13Li have been observed after nucleon-knockout reactions at relativistic energies with 11Li and 14Be beams impinging on a liquid hydrogen target. The channels , and were analysed in the ALADIN-LAND setup at GSI. The 10Li data confirm earlier findings, while the 12Li and 13Li nuclei were observed for the first time. The relative-energy spectrum shows that the ground state of 12Li can be described as a virtual s-state with a scattering length of -13.7(1.6) fm. A broad energy spectrum was found for the channel. Based on the assumption that the relative-energy spectrum is dominated by a correlated background presumably stemming from initial correlations in the 14Be ground-state, evidence for a 13Li resonance at 1.47(31) MeV above the threshold with a width around 2 MeV has been found.
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17.
  • Aksyutina, Yuliya, 1983, et al. (författare)
  • Properties of the 7He ground state from 8He neutron knockout
  • 2009
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 679:3, s. 191-196
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
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18.
  • Baumann, T., et al. (författare)
  • Longitudinal momentum distributions of C-16,C-18 fragments after one-neutron removal from C-17,C-19
  • 1998
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 439:3-4, s. 256-261
  • Tidskriftsartikel (refereegranskat)abstract
    • The fragment separator FRS at GSI was used as an energy-loss spectrometer to measure the longitudinal momentum distributions of C-16,C-18 fragments after one-neutron removal reactions in C-17,C-19 impinging on a carbon target at about 910 MeV/u. The distributions in the projectile frames are characterized by a FWHM of 141 +/- 6 MeV/c for C-16 and 69 +/- 3 MeV/c for C-18. Th, results are compared with experimental data obtained at lower energies and discussed within existing theoretical models. (C) 1998 Elsevier Science B.V. AU rights reserved.
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19.
  • Chulkov, L. V., et al. (författare)
  • Three-body correlations in electromagnetic dissociation of Borromean nuclei: The He-6 case
  • 2005
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 759:1-2, s. 23-42
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissociation of He-6 on a lead target has been studied at 240 MeV/u. The four-momenta of the two neutrons in coincidence with alpha-particles have been measured and used to reconstruct the three-body energy and angular correlations in the final state. For the first time, three-body correlations were included in the analysis of the He-6 dissociation data, and compared with calculations assuming a dipole mode for the electromagnetic dissociation. In addition, the experimental data have been analyzed using a series expansion of the final transition amplitude into hyperspherical functions, showing the importance of both nn and alpha n final-state interactions. It is shown that the dissociation process is governed by a transition of one neutron from the p-shell in the 6He ground state to the s-shell in the continuum further indicating that the role of the transition through an intermediate He-5(3/2(-)) state is more important than expected. (c) 2005 Elsevier B.V. All rights reserved.
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20.
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21.
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22.
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23.
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24.
  • Markenroth, Karin, 1973, et al. (författare)
  • He-8-He-6: a comparative study of nuclear fragmentation reactions
  • 2001
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 679:3-4, s. 462-480
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissociation of 227 MeV/u He-8 in a carbon target has been studied in kinematically complete experiments. The data include the relative energy spectrum, angular distributions in the neutron knock-out channel (He-6 + n) as well as diffractive dissociation and inelastic scattering into the (He-6 + 2n) channel. The data are compared with corresponding results from the well-known halo nucleus He-6. In both cases it is found that neutron knock-out is the: dominating reaction channel. The relative energy spectrum (He-6 + n) shows a structure, which is interpreted as being due to the I-pi = 3/2(-) resonance in the He-7 ground state with about equal contribution from its I-pi = 1/2(-) spin-orbit partner. The He-7 resonance shows a spin alignment similar to that observed in He-5, but with a smaller anisotropy indicating that the structure of the He-8 ground state is more complicated than that of He-6. The data in the (He-6 + 2n) channel were used to identify resonances in the excitation energy spectrum of He-8. If the spectrum is interpreted as two overlapping resonances, the spin-parity assignment for these is found to be 2(+) and 1(-), respectively.
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25.
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26.
  • Simon, H., et al. (författare)
  • Systematic investigation of the drip-line nuclei 11Li and 14Be and their unbound subsystems 10Li and 13Be
  • 2007
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 791:3-4, s. 267-
  • Tidskriftsartikel (refereegranskat)abstract
    • Fragmentation reactions in a carbon target with beams of 11Li and 14Be at relativistic energies have been studied in a kinematically complete experiment at the ALADIN-LAND setup at GSI. Excited states in 11Li and 14Be were obtained from the data in the inelastic channel. The measured cross sections with the core nucleus in the final state show that in the 14Be case core polarization plays an important role. In the one-neutron knockout channels the measured angular correlations between fragment and neutron are asymmetric, which demonstrates the presence of states with different parities in the 11Li and 14Be ground states. For 10Li a low-lying virtual s-state, a p-state and evidence for a d-state could be extracted from the data, while the 12Be+n system shows resonances with more complicated structure.
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27.
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28.
  • Bhattacharyya, A., et al. (författare)
  • Neutron capture cross sections of light neutron-rich nuclei relevant for -process nucleosynthesis
  • 2021
  • Ingår i: Physical Review C. - 2469-9993 .- 2469-9985. ; 104:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning scenario. In the quest of -process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section (, ) for was inferred from the Coulomb dissociation of at intermediate energy ( MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of , , , and . The reaction cross sections were inferred indirectly through Coulomb dissociation of , , and at incident projectile energies around 400-430 MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical -process temperatures were obtained from the measured () capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, , , and are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for and but in the case of the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For , the measured cross section is about higher than the Hauser-Feshbach prediction.
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29.
  • Chakraborty, S., et al. (författare)
  • Ground-state configuration of neutron-rich Al-35 via Coulomb breakup
  • 2017
  • Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 96:3, s. 1965-
  • Tidskriftsartikel (refereegranskat)abstract
    • The ground-state configuration of Al-35 has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of similar to 403 MeV/nucleon. The measured inclusive differential CD cross section for Al-35, integrated up to 5.0 MeV relative energy between the Al-34 core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of 34Al is 29(7) mb. The differential CD cross section of Al-35 -> Al-34 + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of Al-35 could be, tentatively, 1/2+ or 3/2(+) or 5/2(+). The valence neutrons, in the ground state of Al-35, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the Al-34 core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2+ is the ground-state spin-parity of Al-35 as suggested in the literature, then the major ground-state configuration of Al-35 is a combination of Al-34(g. s.; 4(-)) circle times upsilon(p3/2) and Al-34(isomer; 1(+)) circle times upsilon(d3/2) states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.
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30.
  • Chakraborty, S., et al. (författare)
  • Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb breakup
  • 2014
  • Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 66
  • Konferensbidrag (refereegranskat)abstract
    • Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s) - νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al. © Owned by the authors, published by EDP Sciences, 2014.
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31.
  • Cortina-Gil, D., et al. (författare)
  • One-neutron knockout of O-23
  • 2005
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 25, s. 343-346
  • Konferensbidrag (refereegranskat)abstract
    • Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope O-23. The O-22 fragments produced in one-nucleon removal from O-23 at 938 MeV/nucleon in a carbon target were detected in coincidence with de-exciting gamma rays, allowing to discern between 220 ground-state and excited-states contributions. From the comparison of exclusive experimental momentum distributions for the one-neutron removal channel to theoretical momentum distributions calculated in an Eikonal model for the knockout process, and spin and parity assignment of I-pi = 1/2(+) was deduced for the 230 ground state. This result solved the existent experimental discrepancy.
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32.
  • Datta, U., et al. (författare)
  • Direct experimental evidence for a multiparticle-hole ground state configuration of deformed Mg-33
  • 2016
  • Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 94:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich Mg-33 isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part similar to(70 +/- 13)% of the cross section is observed to populate the excited states of Mg-32 after the Coulomb breakup of Mg-33. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s(1/2) and p(3/2) orbitals. These experimental findings suggest a significant reduction and merging of sd-pf shell gaps at N similar to 20 and 28. The ground state configuration of Mg-33 is predominantly a combination of Mg-32(3.0,3.5MeV; 2(-), 1(-)) circle times nu(s1/2), Mg-32(2.5MeV; 2(+)) circle times nu(p3/2), and Mg-32(0; 0(+)) circle times nu(p3/2). The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N = 20.
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33.
  • Meister, Mikael, 1969, et al. (författare)
  • High-energy breakup of 8B
  • 2003
  • Ingår i: Nucl. Phys. A. ; 718, s. 431-433
  • Konferensbidrag (refereegranskat)
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34.
  • Rahaman, A., et al. (författare)
  • Coulomb breakup of neutron-rich Na-29,Na-30 isotopes near the island of inversion
  • 2017
  • Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 44:4, s. 045101-
  • Tidskriftsartikel (refereegranskat)abstract
    • First results are reported on the ground state configurations of the neutron-rich Na-29,Na-30 isotopes, obtained via Coulomb dissociation (CD) measurements. The invariant mass spectra of these nuclei have been obtained through measurement of the four-momenta of all decay products after Coulomb excitation of those nuclei on a Pb-208 target at energies of 400-430 MeV/nucleon using the FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated inclusive CD cross-sections (CD) of 89 (7) mb and 167 (13) mb for one neutron removal from Na-29 and Na-30, respectively, have been extracted up to an excitation energy of 10 MeV. The major part of one neutron removal, CD cross-sections of those nuclei populate the core, in its ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of Na-29 (3/2(+)) and Na-30 (2(+)) is the d-orbital with a small contribution from the s-orbital, which are coupled with the ground state of the core. One of the major components of the ground state configurations of these nuclei are Na-28(gs)(1(+)) circle times v(s,d) and Na-29(gs)(3/2(+)) circle times v(s,d), respectively. The ground state spin and parity of these nuclei obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the s and d orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with shell model calculation using the MCSM suggests a lower limit of around 4.3 MeV of the sd-pf shell gap in Na-30.
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35.
  • Rahaman, A., et al. (författare)
  • Study of ground state wave-function of the Neutron-rich 29,30Na isotopes through coulomb breakup
  • 2014
  • Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 66
  • Konferensbidrag (refereegranskat)abstract
    • Coulomb breakup of unstable neutron rich nuclei 29,30Na around the 'island of inversion' has been studied at energy around 434 MeV/nucleon and 409 MeV/nucleon respectively. Four momentum vectors of fragments, decay neutron from excited projectile and γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence. For these nuclei, the low-lying dipole strength above one neutron threshold can be explained by direct breakup model. The analysis for Coulomb breakup of 29,30Na shows that large amount of the cross section yields the 28Na, 29Na core in ground state. The predominant ground-state configuration of 29,30Na is found to be 28Na(g.s) νs1/2 and 29Na(g.s) νs1/2,respectively. © Owned by the authors, published by EDP Sciences, 2014.
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36.
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37.
  • Andreyev, A. N., et al. (författare)
  • alpha-decay of the new isotope Po-187 : Probing prolate structures beyond the neutron mid-shell at N=104
  • 2006
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 73:4, s. 044324-
  • Tidskriftsartikel (refereegranskat)abstract
    • The new neutron-deficient isotope Po-187 has been identified in the complete fusion reaction Ti-46+Sm-144 -> Po-187+3n at the velocity filter SHIP. Striking features of the Po-187 alpha decay are the strongly-hindered decay to the spherical ground state and unhindered decay to a surprisingly low-lying deformed excited state at 286 keV in the daughter nucleus Pb-183. Based on the potential energy surface calculations, the Po-187 ground state and the 286 keV excited state in Pb-183 were interpreted as being of prolate origin. The systematic deviation of the alpha-decay properties in the lightest odd-A Po isotopes relative to the smooth behavior in the even-A neighbors is discussed. Improved data for the decay of Bi-187(m,g) were also obtained.
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38.
  • Andreyev, A. N., et al. (författare)
  • New microsecond isomers in Bi-189,Bi-190
  • 2001
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 10:2, s. 129-133
  • Tidskriftsartikel (refereegranskat)abstract
    • New microsecond isomers in the neutron-deficient isotopes Bi-189g,Bi-190 have been identified after in-flight separation by the velocity filter SHIP. The evaporation residues were identified on the basis of delayed recoil-gamma /X-ray, recoil-gamma /X-ray-alpha and excitation function measurements. The systematics of the [pi 1i(13/2)]13/2(+) excited states in the odd-mass Bi nuclei is discussed.
  •  
39.
  • Andreyev, A. N., et al. (författare)
  • Shape-changing particle decays of Bi-185 and structure of the lightest odd-mass Bi isotopes
  • 2004
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69:5, s. 054308-
  • Tidskriftsartikel (refereegranskat)abstract
    • Proton and alpha decay of the proton-rich nuclide Bi-185 has been restudied in more detail in the complete fusion reaction Nb-93(Mo-95, 3n)Bi-185 at the velocity filter SHIP. The observed decay pattern of Bi-185 and of the heavier odd-mass isotopes Bi-187,Bi-189,Bi-191,Bi-193 are interpreted based on potential-energy surface calculations. It is shown that the experimental systematics of the particle decays and of the excited states in these nuclei (where known) can be explained by the prolate-oblate shape co-existence at low excitation energy. The observed state in Bi-185 is proposed to be of prolate nature, which is in contrast with the previously proposed oblate interpretation.
  •  
40.
  • Andreyev, A. N., et al. (författare)
  • The discovery of a prolate-oblate-spherical shape triple of spin 0(+) states in the atomic nucleus Pb-186
  • 2001
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 682, s. 482C-486C
  • Tidskriftsartikel (refereegranskat)abstract
    • Two excited J(pi)=0(+) states in Pb-186 populated in the a-decay of Po-190 have been identified through alpha -particle/conversion electron coincidences in an experiment at the velocity filter SHIP. The parent Po-190 nuclei have been produced in the Nd-142(Cr-52,4n)Po-190 complete fusion reaction, alpha -particle energies and branching ratios have been measured and hindrance factors were deduced. The observed states have been interpreted as the band heads of the known prolate and (yet unobserved) oblate rotational bands in Pb-186.
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41.
  • Faestermann, T, et al. (författare)
  • Decay studies of N approximate to Z nuclei from Sr-75 to Sn-102
  • 2002
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 15:1-2, s. 185-188
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron deficient nuclei near Sn-100 have been produced by fragmentation of a 1 (.) A GeV Sn-112 beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector measured the total energy of emitted beta(+)-particles. gamma-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei Rh-90, Ag-94 and In-98 we observed for the first time fast beta-decays, compatible with superallowed Fermi transitions and confirmed such decays for 78y, 82 Nb and Tc. We have also observed 'long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from _Zr up to addition we find the proton drip line nucleus Y-77 to decay dominantly via beta-decay, To study the Gamov-Teller strength in the beta-decay near the doubly magic Sn-102 we measured the half-life, beta- and gamma-spectrum of Sn-102. We propose a level scheme for the daughter nuclide In-102 and deduce the Qamov-Teller strength (B-GT = 4.0 +/- 0.6). This is one of the largest values known.
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42.
  • Van de Vel, K., et al. (författare)
  • Fine structure in the alpha decay of Po-188,Po-192
  • 2003
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 68:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The alpha decay of Po-188,Po-192 has been reexamined in order to probe the 0(+) states in the daughter nuclei Pb-184,Pb-188 that can be associated with coexisting spherical, oblate, and/or prolate configurations. Improved values were measured for the excitation energy and the feeding alpha -decay intensity of the 0(2)(+) state in Pb-184,Pb-188 and conflicting results on the 0(3)(+) state in Pb-188 were clarified. All known cases of fine structure in the alpha decay of the even-even Po nuclei are reviewed. The reduced alpha-decay width systematics combined with potential-energy-surface calculations confirm the onset of deformation in the ground state of the polonium nuclei around the neutron midshell. An isomeric state with a half-life of 580(100)ns has been identified in Po-192 .
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43.
  • Van de Vel, K., et al. (författare)
  • Prolate structures in Po-189 and Pb-185
  • 2005
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 24:1, s. 57-62
  • Tidskriftsartikel (refereegranskat)abstract
    • The 3/2(-) isomer in Pb-185 and states above it have been populated in the α-decay of Po-189. The observed α-decay strengths to and the electromagnetic decay properties of the excited states in Pb-185 have been combined with Potential Energy Surface and Particle-Plus-Rotor calculations to propose configuration assignments. It is suggested that the α-decaying isomer of Po-189 is of prolate origin and that the prolate configuration becomes very low in energy in Pb-185.
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