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Sökning: WFRF:(Grévy S)

  • Resultat 1-22 av 22
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1.
  • Girard-Alcindor, V., et al. (författare)
  • New narrow resonances observed in the unbound nucleus F 15
  • 2022
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 105:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the unbound F15 nucleus is investigated using the inverse kinematics resonant scattering of a radioactive O14 beam impinging on a CH2 target. The analysis of H1(O14,p)O14 and H1(O14,2p)N13 reactions allowed the confirmation of the previously observed narrow 1/2- resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2- and 3/2- resonances. The newly observed levels decay by 1p emission to the ground of O14, and by sequential 2p emission to the ground state of N13 via the 1- resonance of O14. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2- and 3/2- resonances may be collectivized by the continuum coupling to nearby 2p- and 1p-decay channels. The observed excitation function H1(O14,p)O14 and resonance spectrum in F15 are well reproduced in the unified framework of the GSM.
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2.
  • Sguazzin, M., et al. (författare)
  • Determining neutron-induced reaction cross sections through surrogate reactions at storage rings
  • 2023
  • Ingår i: Journal of Physics: Conference Series. - 1742-6588 .- 1742-6596. ; 2586:1
  • Konferensbidrag (refereegranskat)abstract
    • Determining the cross sections of neutron-induced reactions on short-lived nuclei is imperative to rate calculations in stellar nucleosynthesis and applications of nuclear physics. It is also an immense experimental challenge due to the radioactivity of the targets involved. Our goal is to circumvent this obstacle by using surrogate reactions in inverse kinematics at the heavy-ion storage rings of GSI/FAIR. We present here preliminary results from the first proof of principle experiment, where a beam of 208Pb impinged on a H2 gas jet target in the Experimental Storage Ring (ESR).
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3.
  • Sguazzin, M., et al. (författare)
  • Indirect measurements of neutron -induced reaction cross sections at heavy -ion storage rings
  • 2023
  • Ingår i: 15TH INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY, ND2022. - 2100-014X. ; 284
  • Konferensbidrag (refereegranskat)abstract
    • Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars and for applications in nuclear technology. However, their measurement is very complicated due to the radioactivity of the targets involved. We propose to circumvent this problem by using the surrogate reaction method in inverse kinematics, where the nucleus formed in the neutroninduced reaction of interest is produced by a reaction involving a radioactive heavy -ion beam and a stable, light target nucleus. The probabilities as a function of the compound -nucleus excitation energy for y -ray emission, neutron emission and fission, which can be measured with the surrogate reaction, are particularly useful to constrain model parameters and to obtain more accurate predictions of the neutron-induced reaction cross sections of interest. Yet, the full development of the surrogate method is hampered by numerous longstanding target issues, which can be solved by combining surrogate reactions with the unique and largely unexplored possibilities at heavy -ion storage rings. In this contribution, we describe the developments we are carrying out to measure for the first time simultaneously y-ray emission, neutron emission and fission probabilities at the storage rings of the GSI/FAIR facility. In particular, we will present the first results of the proof of principle experiment, which we performed in June 2022 at the Experimental Storage Ring (ESR)
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4.
  • Sguazzin, M., et al. (författare)
  • Indirect measurements of neutron-induced reaction cross sections at storage rings
  • 2023
  • Ingår i: NUCLEAR PHYSICS IN ASTROPHYSICS - X, NPA-X 2022. - : EDP Sciences. - 2100-014X. ; 279
  • Konferensbidrag (refereegranskat)abstract
    • Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars. However, their measurement is very difficult due to the radioactivity of the targets involved. We propose to circumvent this problem by using for the first time the surrogate reaction method in inverse kinematics at heavy-ion storage rings. In this contribution, we describe the developments we have done to perform surrogate-reaction studies at the storage rings of GSI/FAIR. In particular, we present the first results of the proof of principle experiment, which we conducted recently at the Experimental Storage Ring (ESR).
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5.
  • Markenroth, Karin, 1973, et al. (författare)
  • Crossing the dripline to N-11 using elastic resonance scattering
  • 2000
  • Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 6203:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The level structure of the unbound nucleus N-11 has been studied by C-10+p elastic resonance scattering in inverse geometry with the LISE3 spectrometer at GANIL, using a C-10 beam with an energy of 9.0 MeV/ nucleon. An additional measurement was done at the A1200 spectrometer at MSU. The excitation function above the C-10+p threshold has been determined up to 5 MeV. A potential-model analysis revealed three resonance states at energies 1.27(-0.05)(+0.18) MeV (Gamma = 1.44 +/- 0.2 MeV), 2.01(-0.05)(+0.15) MeV (Gamma = 0.84 +/- 0.2 MeV), and 3.75 +/- 0.05 MeV (Gamma = 0.60 +/- 0.05 MeV) with the spin-parity assignments I-pi=1/2+,1/2,-,5/2+, respectively. Hence, N-11 is shown to have a ground state parity inversion completely analogous to its mirror partner Be-11. A narrow resonance in the excitation function at 4.33 +/- 0.05 MeV was also observed and assigned spin parity 3/2-.
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6.
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7.
  • Axelsson, L., et al. (författare)
  • Study of the unbound nucleus 11N by elastic resonance scattering
  • 1996
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 2469-9985 .- 2469-9993. ; 54:4, s. 1511-1514
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonances in the unbound nucleus 11N have been studied, using the resonance scattering reaction 10C+p. The data give evidence for three states above the 10C+p threshold with energies 1.30, 2.04, and 3.72 MeV. These states can be interpreted, in a potential-model analysis, as the ground state and the first two excited states with spin-parity 1 / 2+, 1 / 2-, and 5 / 2+ arising from the shell-model orbitals 1s1 / 2, 0p1 / 2, and 0d5 / 2. A narrow state superposed on a broad structure found at higher energy could be interpreted as the mirror state of the 3 / 2- in 11Be shifted down in energy. This shift would suggest a large radius of the potential.
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8.
  • Caceres, L., et al. (författare)
  • Nuclear structure studies of F-24
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 92:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the F-24 nucleus has been studied at GANIL using the beta decay of O-24 and the in-beam.-ray spectroscopy from the fragmentation of Na-27,Na-28, Ne-25,Ne-26, and Mg-29,Mg-30 nuclei. Combining these complementary experimental techniques, the level scheme of F-24 has been constructed up to 3.6 MeV by means of particle-gamma and particle-gamma gamma coincidence relations. Experimental results are compared to shell-model calculations using the standard USDA and USDB interactions as well as ab initio valence-space Hamiltonians calculated from the in-medium similarity renormalization group based on chiral two- and three-nucleon forces. Both methods reproduce the measured level spacings well, and this close agreement allows unidentified spins and parities to be consistently assigned.
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9.
  • Sarmiento Pico, Luis, et al. (författare)
  • Elucidating the nature of the proton radioactivity and branching ratio on the first proton emitter discovered 53mCo
  • 2023
  • Ingår i: Nature Communications. - 2041-1723. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • The observation of a weak proton-emission branch in the decay of the 3174keV 53mCo isomeric state marked the discovery of proton radioactivity in atomic nuclei in 1970. Here we show, based on the partial half-lives and the decay energies of the possible proton-emission branches, that the exceptionally high angular momentum barriers, lp = 9 and lp = 7, play a key role in hindering the proton radioactivity from 53mCo, making them very challenging to observe and calculate. Indeed, experiments had to wait decades for significant advances in accelerator facilities and multi-faceted state-of-the-art decay stations to gain full access to all observables. Combining data taken with the TASISpec decay station at the Accelerator Laboratory of the University of Jyväskylä, Finland, and the ACTAR TPC device on LISE3 at GANIL, France, we measured their branching ratios as bp1 = 1.3(1)% and bp2 = 0.025(4)%. These results were compared to cutting-edge shell-model and barrier penetration calculations. This description reproduces the order of magnitude of the branching ratios and partial half-lives, despite their very small spectroscopic factors.
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10.
  • Stanoiu, M., et al. (författare)
  • Disappearance of the N=14 shell gap in the carbon isotopic chain
  • 2008
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 78:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of C-17-20(6) nuclei was investigated by means of the in-beam gamma-ray spectroscopy technique using fragmentation reactions of radioactive beams. Based on particle-gamma and particle-gamma gamma coincidence data, level schemes are constructed for the neutron-rich C17-20 nuclei. The systematics of the first excited 2(+) states in the carbon isotopes is extended for the first time to A = 20 showing that in contrast to the case of the oxygen isotopes, the N = 14 subshell closure disappears. Experimental results are compared with shell-model calculations. Agreement between them is found only if a reduced neutron-neutron effective interaction is used. Implications of this reduced interaction in some properties of weakly bound neutron-rich Carbon are discussed.
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11.
  • Stanoiu, M., et al. (författare)
  • Study of drip line nuclei through two-step fragmentation
  • 2004
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 20:1, s. 95-96
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the structure of light neutron-rich nuclei around N = 16 by employing the in-beam gamma-ray spectroscopy technique using the fragmentation of secondary beams of Ne-25,Ne-26, Na-27,Na-28 and Mg-29,Mg-30 isotopes. This secondary-beam cocktail was obtained by the fragmentation of a 36 S beam at 77.5 MeV.A by the SISSI/GANIL facility. By a second-step fragmentation, we have measured gamma-ray-residue coincidences in C17-20 and O-23,O-24 and described the obtained levels in the framework of the shell model.
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12.
  • Stanoiu, M., et al. (författare)
  • Study of neutron rich carbon and oxygen nuclei up to drip line
  • 2004
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 746, s. 135C-139C
  • Tidskriftsartikel (refereegranskat)abstract
    • In-beam gamma-spectroscopy using fragmentation reactions of radioactive beams have been performed in order to study the structure of excited states in neutron rich oxygen and carbon isotopes. For the produced fragments, gamma-ray energies, intensities and gamma-gamma coincidences have been measured. The experiment was performed at GANIL. New gamma-lines have been identified and placed in level schemes for C17-20. The non observation of any gamma-ray in O-23,O-24 suggests that their first excited states lie above the neutron threshold. These results are discussed in the framework of shell model calculations.
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13.
  • Vajta, Zs., et al. (författare)
  • Excited states in the neutron-rich nucleus F-25
  • 2014
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:5, s. 054323-
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the nucleus F-25(9) was investigated through in-beam. gamma-ray spectroscopy of the fragmentation of Ne-26 and Na-27,Na-28 ion beams. Based on the particle-gamma and particle-gamma gamma coincidence data, a level scheme was constructed and compared with shell model and coupled-cluster calculations. Some of the observed states were interpreted as quasi-single-particle states built on top of the closed-shell nucleus O-24, while the others were described as states arising from coupling of a single proton to the 2(broken vertical bar) core excitation of O-24.
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14.
  • Stanoiu, M., et al. (författare)
  • Spectroscopy of (26)F
  • 2012
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 85:1, s. 017303-
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the weakly bound (26)(9)F(17) odd-odd nucleus, produced from (27,28)Na nuclei, has been investigated at GANIL by means of the in-beam gamma-ray spectroscopy technique. A single gamma-line is observed at 657(7) keV in (26)(9)F which has been ascribed to the decay of the excited J = 2(+) state to the J = 1(+) ground state. The possible presence of intruder negative parity states in (26)F is also discussed.
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15.
  • Axelsson, L., et al. (författare)
  • Deriving the angular variation of p(parallel to)-distributions for halo neutrons with robust statistics
  • 2001
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 679:3-4, s. 215-230
  • Tidskriftsartikel (refereegranskat)abstract
    • The longitudinal neutron momentum distribution from core breakup of Li-11 and Be-11 have been measured at 29.9 MeV/u and 38.5 MeV/u, respectively. Separate measurements on Li-9 and Be-10 allowed extraction of the halo neutron distribution. The shapes of the distributions are analyzed using robust and descriptive statistics, For both isotopes the shape is changing with angle. (C) 2001 Elsevier Science B.V. All rights reserved.
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16.
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17.
  • De Oliveira Santos, F., et al. (författare)
  • Study of 19Na at SPIRAL
  • 2005
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 24:2, s. 237-247
  • Tidskriftsartikel (refereegranskat)abstract
    • The excitation function for the elastic-scattering reaction p( 18 Ne, p) 18 Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19 Na. In addition, two-proton emission events have been identified and are discussed.
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18.
  • Giovinazzo, J., et al. (författare)
  • 4D-imaging of drip-line radioactivity by detecting proton emission from 54mNi pictured with ACTAR TPC
  • 2021
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Proton radioactivity was discovered exactly 50 years ago. First, this nuclear decay mode sets the limit of existence on the nuclear landscape on the neutron-deficient side. Second, it comprises fundamental aspects of both quantum tunnelling as well as the coupling of (quasi)bound quantum states with the continuum in mesoscopic systems such as the atomic nucleus. Theoretical approaches can start either from bound-state nuclear shell-model theory or from resonance scattering. Thus, proton-radioactivity guides merging these types of theoretical approaches, which is of broader relevance for any few-body quantum system. Here, we report experimental measurements of proton-emission branches from an isomeric state in 54mNi, which were visualized in four dimensions in a newly developed detector. We show that these decays, which carry an unusually high angular momentum, ℓ = 5 and ℓ = 7, respectively, can be approximated theoretically with a potential model for the proton barrier penetration and a shell-model calculation for the overlap of the initial and final wave functions.
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19.
  • Giovinazzo, J., et al. (författare)
  • Proton 3D tracking and emission time from a short-lived isomer with ACTAR TPC
  • 2022
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1042
  • Tidskriftsartikel (refereegranskat)abstract
    • An experiment was conducted at the GANIL/LISE3 facility to produce the 10+ isomer of 54Ni and measure its proton radioactivity decay branches. The proton detection was achieved with the ACTAR TPC device that enabled the separation of the small signal of the emitted proton from the large signal of the implanted ion, while the decay half-life is of the order of 150 ns. From the measured data, the emitted proton track length and the decay time of the ion can be extracted simultaneously. The full proton radioactivity pattern could be established, with two emission branches and their relative branching ratio. Data processing and analysis that allowed to identify and separate the ion and the proton signals in order to reconstruct the particles trajectories and decay time are detailed. The evaluation of the detection efficiency for the proton radioactivity branches based on a full simulation is described.
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20.
  • Grevy, S., et al. (författare)
  • Core-breakup reactions of the halo nuclei Be-11 and Li-11: momentum distributions and shadow effects
  • 1999
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 650:1, s. 47-61
  • Tidskriftsartikel (refereegranskat)abstract
    • The halo nuclei Be-11 and Li-11 have been studied in core-breakup reactions where the halo neutrons are expected to be released without a major distortion due to the reaction. The widths of the halo-neutron momentum distributions have been extracted in coincidence with He fragments, Gamma = 32 +/- 4 MeV/c, and Li fragments, Gamma = 42 +/- 4 MeV/c for Be-11 and with He fragments, Gamma =42+/-6 MeV/c for Li-11. The Be-11 breakup gives a very low neutron multiplicity of 0.38+/-0.09 which is a manifestation of the shadowing of the neutron in the core-breakup reaction. This value can be understood from a simple theoretical calculation, which also accounts for the observed transverse momentum widths at small angles. (C) 1999 Elsevier Science B.V.
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21.
  • Marques, F. M., et al. (författare)
  • Neutrons from the breakup of C-19
  • 1996
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 381:4, s. 407-412
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutrons arising from the breakup of a 30 MeV/nucleon C-19 beam on a tantalum target have been measured using the 98 element array DEMON. A narrow, forward peaked neutron angular distribution, with a corresponding momentum spread considerably smaller than those measured simultaneously for N-21, O-22 and F-24 was observed for charged fragments with Z
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22.
  • Rudolph, D., et al. (författare)
  • Mirror symmetry at mass A = 54: E4 effective charges near doubly magic 56Ni
  • 2022
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 830
  • Tidskriftsartikel (refereegranskat)abstract
    • Proton-emission branches of the 10+ isomer in the Tz=−1 nucleus 54Ni have been imaged with the active target and time projection chamber (ACTAR TPC) in an experiment conducted at the Grand Accélérateur National d'Ions Lourds (GANIL). The completed decay scheme allows derivation of the reduced transition strengths, B(E2;10+→8+) and B(E4;10+→6+), for the two competing γ-ray transitions. By means of a comparison with their well-known ‘mirror transitions’ in Tz=+1 54Fe, and aided by a variety of shell-model calculations in the fp model space, effective charges for E4 transitions near N=Z 56Ni can be deduced: επ≈1.40 and εν≈0.30. Mirror-energy differences are explored with various shell-model interactions and isospin-symmetry breaking terms.
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