Proton-induced knockout reactions with polarized and unpolarized beams

Wakasa, T.; Ogata, Kazuyuki; Noro, T.

doi:10.1016/j.ppnp.2017.06.002

Cited by 84 publications

(92 citation statements)

References 135 publications

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“…Because of the structure of the wave function of the value of 0.04 (29) mb for the first excited state were found, leaving at least 4.1(9) mb that will mainly belong to states that in their wave function contain a hole in the πf 7=2 orbital. Theoretical single-particle cross sections were calculated using the distorted-wave impulse approximation (DWIA) framework [52] and averaged along the thick target, the beam energy decreasing from 270 to 180 MeV per nucleon. The optical potentials for the incoming proton and the outgoing two protons are obtained by a microscopic framework; the Melbourne nucleon-nucleon G-matrix interaction [53] is folded by a nuclear density calculated with the Bohr-Mottelson single-particle potential [54].…”

Section: − If This Level Is a 1=2mentioning

confidence: 99%

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
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In-beam γ-ray spectroscopy of 79 Cu is performed at the Radioactive Isotope Beam Factory of RIKEN. The nucleus of interest is produced through proton knockout from a 80Zn beam at 270 MeV=nucleon. The level scheme up to 4.6 MeV is established for the first time and the results are compared to Monte Carlo shell-model calculations. We do not observe significant knockout feeding to the excited states below 2.2 MeV, which indicates that the Z ¼ 28 gap at N ¼ 50 remains large. The results show that the 79 Cu nucleus can be described in terms of a valence proton outside a 78Ni core, implying the magic character of the latter. DOI: 10.1103/PhysRevLett.119.192501 The shell model constitutes one of the main building blocks of our understanding of nuclear structure. Its robustness is well proven for nuclei close to the valley of stability, where it successfully predicts and explains the occurrence of magic numbers [1,2]. However, these magic numbers are not universal throughout the nuclear chart and their evolution far from stability, observed experimentally over the last decades, has generated much interest [3]. For example, the magic numbers N ¼ 20 and 28 may disappear [4][5][6][7] while new magic numbers arise at N ¼ 14, 16 and 32, 34, respectively [8][9][10][11][12][13]. Although shell gaps, defined within a given theoretical framework as differences of effective single-particle energies (ESPE), are not observables [14], they are useful quantities to assess the underlying structure of nuclei [15][16][17]. The nuclear potential acting on nuclei far from stability can induce drifts of the single-particle orbitals and their behavior as a function of isospin can be understood within the shell model [18][19][20][21][22]. Difficulties arise, however, when the single-particle properties are masked by correlations that stem from residual interactions and discriminating between the two effects is nontrivial.In the shell model as it was initially formulated, the proton πf 7=2 orbital separates from the 3ℏω harmonic oscillator shell because of the spin-orbit splitting and forms the Z ¼ 28 gap. The neutron νg 9=2 orbital splits off from the 4ℏω shell to join the 3ℏω orbits and creates a magic number at N ¼ 50. With 28 protons and 50 neutrons, the 78 Ni nucleus is thus expected to be one of the most neutronrich doubly magic nuclei, making it of great interest for nuclear structure. Up to now, no evidence has been found for the disappearance of the shell closures at Z ¼ 28

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Section: − If This Level Is a 1=2mentioning

confidence: 99%

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
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“…The uncertainty in the DWIA framework and its input is about 20% as discussed in Ref. [42]. Above 4 MeV, only those excited states are shown for which the theoretical cross section exceeds 0.1 mb.…”

Section: For the B(m1)mentioning

confidence: 95%

“…[3][4][5][6][7]). For larger neutron numbers the magicity of N = 28 was also proved to be soft; for example, in the 42 Si nucleus [8,9]. Regarding the protons, there are accumulating pieces of evidence for a new magic number at 6 in addition to 8 for neutron-rich carbon isotopes [10].…”

Section: Introductionmentioning

confidence: 99%

Nuclear structure of Ni76 from the ( p,2p ) reaction

Elekes¹,

Kripkó²,

Sohler³

et al. 2019

Phys. Rev. C

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The nuclear structure of the 76 Ni nucleus was investigated by (p, 2p) reaction using a NaI(Tl) array to detect the deexciting prompt γ rays. A new transition with an energy of 2227 keV was identified by γ γ and γ γ γ coincidences. According to these coincidence spectra the observed transition connects a new state at 4147 keV and the previously known 4 + 1 state at 1920 keV. Two weaker transitions were also obtained at 2441 and 2838 keV, which could be tentatively placed to feed the known 2 + 1 state at 990 keV. Our shell-model calculations using the Lenzi, Nowacki, Poves, and Sieja interaction produced good candidates for the experimental proton hole states in the observed energy region, and the theoretical cross sections showed good agreement with the experimental values. Although we could not assign all the experimental states to the theoretical ones unambiguously, the results are consistent with a reasonably large Z = 28 shell gap for nickel isotopes in accordance with previous studies.

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“…Observed odd-even staggering in fragmentation cross sections has been understood as originating from the low particle separation energy and level density of the daughter nucleus [5][6][7]. One-nucleon knockout reactions are a tool of choice for spectroscopic studies, and exclusive cross sections between individual excited states may characterize the overlap between the initial and final wavefunctions [8,9]. Despite the pervasiveness of these methods, the relevant quantities that drive single nucleon removal cross sections are still actively studied [10][11][12][13][14][15].…”

mentioning

confidence: 99%

“…Figure 1 shows the secondary beams exploited for this analysis, which extend over a region heretofore unexplored by single nucleon removal inclusive cross section studies. A 238 U primary beam accelerated to 345 MeV/nucleon impinged upon a 3-mm thick 9 Be production target, creating a cocktail of radioactive isotopes through in-flight fission at the entrance of the BigRIPS spectrometer [44]. The mean primary beam intensity was 12 pnA for settings 1-3, and 30 pnA for settings 4-6.…”

mentioning

confidence: 99%

Prominence of Pairing in Inclusive (p,2p) and (p,pn
Paul¹,
Obertelli²,
Bertulani³
et al. 2019
Phys. Rev. Lett.
7
0
3
0
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Fifty-five inclusive single nucleon removal cross sections from medium mass neutron-rich nuclei impinging on a hydrogen target at ∼ 250 MeV/nucleon were measured at the RIKEN Radioactive Isotope Beam Factory. Systematically higher cross sections are found for proton removal from nuclei with an even number of protons compared to odd-proton number projectiles for a given neutron separation energy. Neutron removal cross sections display no even-odd splitting contrary to nuclear cascade model predictions. Both effects are understood through simple considerations of neutron separation energies and bound state level densities originating in pairing correlations in the daughter nuclei. These conclusions are supported by comparison with semi-microscopic model predictions, highlighting the enhanced role of low-lying level densities in nucleon removal cross sections from loosely-bound nuclei. Pairing correlations, which lower the energy of an atomic nucleus by coupling nucleons into spin-zero pairs, play a prominent role in nuclear structure [1, 2]. They are responsible, for example, for the odd-even mass and nucleon separation energy staggering along isotopic chains and the reduced level density in the low-energy spectra

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Proton-induced knockout reactions with polarized and unpolarized beams

Cited by 84 publications

References 135 publications

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
Self Cite

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
Self Cite

Nuclear structure of Ni76 from the ( p,2p ) reaction

Prominence of Pairing in Inclusive (p,2p) and (p,pn
Paul¹,
Obertelli²,
Bertulani³
et al. 2019
Phys. Rev. Lett.
7
0
3
0
View full text Add to dashboard Cite

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Proton-induced knockout reactions with polarized and unpolarized beams

Cited by 84 publications

References 135 publications

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of Olivier1, Franchoo2, Nııkura3 et al. 2017Phys. Rev. Lett.Self Cite

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of Olivier1, Franchoo2, Nııkura3 et al. 2017Phys. Rev. Lett.Self Cite

Nuclear structure of Ni76 from the ( p,2p ) reaction

Prominence of Pairing in Inclusive (p,2p) and (p,pnPaul1, Obertelli2, Bertulani3 et al. 2019Phys. Rev. Lett.7030View full textAdd to dashboardCite

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Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
Self Cite

Persistence of the Z=28 Shell Gap Around Ni78 : First Spectroscopy of
Olivier¹,
Franchoo²,
Nııkura³
et al. 2017
Phys. Rev. Lett.
Self Cite

Prominence of Pairing in Inclusive (p,2p) and (p,pn
Paul¹,
Obertelli²,
Bertulani³
et al. 2019
Phys. Rev. Lett.
7
0
3
0
View full text Add to dashboard Cite