| 1. |
- Aksouh, F., et al.
(author)
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STUDY OF THE O-15(2p,gamma)Ne-17 CROSS SECTION BY COULOMB DISSOCIATION OF Ne-17 FOR THE rp PROCESS OF NUCLEOSYNTHESIS
- 2014
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In: Acta Physica Polonica, Series B.. - 1509-5770 .- 0587-4254. ; 45:2, s. 229-234
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Journal article (peer-reviewed)abstract
- The O-15(2p, gamma)Ne-17 cross section has been studied by the inverse reaction, the Coulomb dissociation of Ne-17. The experiment has been performed at the GSI. The Ne-17 excitation energy prior to decay has been reconstructed by using the invariant-mass method. The preliminary differential and integral Coulomb dissociation cross sections (sigma(Coul)) have been extracted, which provide a photoabsorption (sigma(photo)) and a radiative capture cross section (sigma(cap)). Additionally, important information about the Ne-17 nuclear structure will be obtained. The analysis is in progress.
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| 2. |
- Johansson, Håkan T, 1977, et al.
(author)
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The unbound isotopes He-9,He-10
- 2010
-
In: Nuclear Physics A. - Elsevier : Elsevier BV. - 0375-9474 .- 1873-1554. ; 842:1-4, s. 15-32
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Journal article (peer-reviewed)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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| 3. |
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| 4. |
- Lehr, C., et al.
(author)
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Unveiling the two-proton halo character of 17 Ne: Exclusive measurement of quasi-free proton-knockout reactions
- 2022
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 827
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Journal article (peer-reviewed)abstract
- The proton drip-line nucleus 17Ne is investigated experimentally in order to determine its two-proton halo character. A fully exclusive measurement of the 17Ne(p,2p)16F→15⁎O+p quasi-free one-proton knockout reaction has been performed at GSI at around 500 MeV/nucleon beam energy. All particles resulting from the scattering process have been detected. The relevant reconstructed quantities are the angles of the two protons scattered in quasi-elastic kinematics, the decay of 16F into 15O (including γ decays from excited states) and a proton, as well as the 15O+p relative-energy spectrum and the 16F momentum distributions. The latter two quantities allow an independent and consistent determination of the fractions of l=0 and l=2 motion of the valence protons in 17Ne. With a resulting relatively small l=0 component of only around 35(3)%, it is concluded that 17Ne exhibits a rather modest halo character only. The quantitative agreement of the two values deduced from the energy spectrum and the momentum distributions supports the theoretical treatment of the calculation of momentum distributions after quasi-free knockout reactions at high energies by taking into account distortions based on the Glauber theory. Moreover, the experimental data allow the separation of valence-proton knockout and knockout from the 15O core. The latter process contributes with 11.8(3.1) mb around 40% to the total proton-knockout cross section of 30.3(2.3) mb, which explains previously reported contradicting conclusions derived from inclusive cross sections.
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| 5. |
- Marganiec, J., et al.
(author)
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Coulomb and nuclear excitations of narrow resonances in 17Ne
- 2016
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 759, s. 200-205
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Journal article (peer-reviewed)abstract
- New experimental data for dissociation of relativistic 17Ne projectiles incident on targets of lead, carbon, and polyethylene targets at GSI are presented. Special attention is paid to the excitation and decay of narrow resonant states in 17Ne. Distributions of internal energy in the O15+p+p three-body system have been determined together with angular and partial-energy correlations between the decay products in different energy regions. The analysis was done using existing experimental data on 17Ne and its mirror nucleus 17N. The isobaric multiplet mass equation is used for assignment of observed resonances and their spins and parities. A combination of data from the heavy and light targets yielded cross sections and transition probabilities for the Coulomb excitations of the narrow resonant states. The resulting transition probabilities provide information relevant for a better understanding of the 17Ne structure.
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| 6. |
- Marganiec, J., et al.
(author)
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Coulomb breakup of 17Ne from the viewpoint of nuclear astrophysics
- 2012
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In: Proceedings of Science. - Proceedings of Science : Sissa. - 1824-8039.
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Conference paper (peer-reviewed)abstract
- By the Coulomb breakup of 17Ne, the time-reversed reaction 15O(2p,γ)17Ne has been studied. This reaction might play an important role in the rp process, as a break-out reaction of the hot CNO cycle. The secondary 17Ne ion beam with an energy of 500 MeV/nucleon has been dissociated in a Pb target. The reaction products have been detected with the LAND-R3B experimental setup at GSI. The preliminary differential and integral Coulomb dissociation cross section sCoul has been determined, which then will be converted into a photo-absorption cross section sphoto, and a two-proton radiative capture cross section σcap. Additionally, information about the structure of the 17Ne, a potential two-proton halo nucleus, will be received. The analysis is in progress. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
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| 7. |
- Marganiec, J., et al.
(author)
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Studies of continuum states in (16) Ne using three-body correlation techniques
- 2015
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 51:1, s. 1-9
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Journal article (peer-reviewed)abstract
- Two-proton decay of the unbound nucleus Ne-16 , produced in one-neutron knockout from a 500 MeV/u Ne-17 beam, has been studied at GSI. The ground state, at a resonance energy 1.388(15) MeV, ( MeV) above the O-14 +p+p threshold, and two narrow resonances at MeV and 7.57(6) MeV have been investigated. A comparison of the energy difference between the first excited 2(+) state and the 0(+) ground state in Ne-16 with its mirror nucleus C-16 reveals a small Thomas-Ehrman shift (TES) of keV. A trend of the TES for the T = 2 quintet is obtained by completing the known data with a prediction for F-16 obtained from an IMME analysis. The decay mechanisms of the observed three resonances were revealed from an analysis of the energy and angular correlations of the O-14 +p+p decay products. The ground state decay can be considered as a genuine three-body (democratic) mode and the excited states decay sequentially via states in the intermediate nucleus F-15 , the 3.22 MeV state predominantly via the F-15 ground-state resonance, while the 7.57 MeV state decays via the 5/2(+) resonance in F-15 at 2.8 MeV above the O-14 +p+p threshold. Further, from an analysis of angular correlations, the spin-parity of the 7.57 MeV state has been determined as and assigned as the third 2(+) state in Ne-16 based on a comparison with C-16.
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| 8. |
- Reifarth, R., et al.
(author)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Conference paper (peer-reviewed)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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| 9. |
- Wamers, F., et al.
(author)
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Diverse mechanisms in proton knockout reactions from the Borromean nucleus Ne-17
- 2023
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In: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 59
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Journal article (peer-reviewed)abstract
- Nucleon knockout experiments using beryllium or carbon targets reveal a strong dependence of the quenching factors, i.e., the ratio (Rs) of theoretical to the experimental spectroscopic factors (C2S), on the proton-neutron asymmetry in the nucleus under study. However, this dependence is greatly reduced when a hydrogen target is used. To understand this phenomenon, exclusive H-1(Ne-17, 2p F-16) and inclusive C-12(Ne-17, 2p 1(6)F)X, 1(2)C(Ne-17, F-16)X as well as 1H(Ne-17,(16) F)X(X-denotes undetected reaction products) reactions with F-16 in the ground and excited states were anal- ysed. The longitudinal momentum distribution of F-16 and the correlations between the detached protons were studied. In the case of the carbon target, there is a significant deviation from the predictions of the eikonal model. The eikonal approximation was used to extract spectroscopic factor values (CS)-S-2. The experimental (CS)-S-2 value obtained with C target is markedly lower than that for H target. This is interpreted as rescattering due to simultaneous nucleon knockout from both reaction partners, Ne-17 and C-12.
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| 10. |
- Wamers, F., et al.
(author)
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First Observation of the Unbound Nucleus Ne-15
- 2014
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 112:13
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Journal article (peer-reviewed)abstract
- We report on the first observation of the unbound proton-rich nucleus Ne-15. Its ground state and first excited state were populated in two-neutron knockout reactions from a beam of 500 MeV/u Ne-17. The Ne-15 ground state is found to be unbound by 2.522(66) MeV. The decay proceeds directly to O-13 with simultaneous two-proton emission. No evidence for sequential decay via the energetically allowed 2(-) and 1(-) states in F-14 is observed. The Ne-15 ground state is shown to have a strong configuration with two protons in the (sd) shell around O-13 with a 63(5)% (1s(1/2))(2) component.
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