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1. Cross-shell states in 15C: A test for p-sd interactions

Author

J. Lois-Fuentes, B. Fernández-Domínguez, X. Pereira-López, F. Delaunay, W.N. Catford, A. Matta, N.A. Orr, T. Duguet, T. Otsuka, V. Somà, O. Sorlin, T. Suzuki, N.L. Achouri, M. Assié, S. Bailey, B. Bastin, Y. Blumenfeld, R. Borcea, M. Caamaño, L. Caceres, E. Clément, A. Corsi, N. Curtis, Q. Deshayes, F. Farget, M. Fisichella, G. de France, S. Franchoo, M. Freer, J. Gibelin, A. Gillibert, G.F. Grinyer, F. Hammache, O. Kamalou, A. Knapton, Tz. Kokalova, V. Lapoux, B. Le Crom, S. Leblond, F.M. Marqués, P. Morfouace, J. Pancin, L. Perrot, J. Piot, E. Pollacco, D. Ramos, D. Regueira-Castro, C. Rodríguez-Tajes, T. Roger, F. Rotaru, M. Sénoville, N. de Séréville, R. Smith, M. Stanoiu, I. Stefan, C. Stodel, D. Suzuki, J.C. Thomas, N. Timofeyuk, M. Vandebrouck, J. Walshe, and C. Wheldon

Subjects
One neutron pick-up reaction, Neutron-rich carbon isotopes, Phenomenological shell-model, Ab initio calculations, Physics, QC1-999
Abstract

The low-lying structure of 15C has been investigated via the neutron-removal 16C(d,t) reaction. Along with the known bound neutron sd-shell states, unbound p-shell hole states have been observed. The excitation energies and the deduced spectroscopic factors of the cross-shell states are an important measure of the [(p)−1(sd)2] neutron configurations in 15C. Our results show a very good agreement with shell-model calculations using the SFO-tls interaction for 15C. However, this same interaction predicted energies that were too low for the corresponding hole states in the N=9 isotone 17O and adjustment of the p-sd and sd-sd monopole terms was required to match the 17O energies. In addition, the excitation energies and spectroscopic factors have been compared to the first calculations of 15C with the ab initio self-consistent Green's function method employing the NNLOsat interaction. The results show the sensitivity to the size of the N=8 shell gap and highlight the need to go beyond the current truncation scheme.

Published
2023
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2. Intruder configurations in 29Ne at the transition into the island of inversion: Detailed structure study of 28Ne

Author

H. Wang, M. Yasuda, Y. Kondo, T. Nakamura, J.A. Tostevin, K. Ogata, T. Otsuka, A. Poves, N. Shimizu, K. Yoshida, N.L. Achouri, H. Al Falou, L. Atar, T. Aumann, H. Baba, K. Boretzky, C. Caesar, D. Calvet, H. Chae, N. Chiga, A. Corsi, H.L. Crawford, F. Delaunay, A. Delbart, Q. Deshayes, Zs. Dombrádi, C. Douma, Z. Elekes, P. Fallon, I. Gašparić, J.-M. Gheller, J. Gibelin, A. Gillibert, M.N. Harakeh, A. Hirayama, C.R. Hoffman, M. Holl, A. Horvat, Á. Horváth, J.W. Hwang, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, S. Kawase, S. Kim, K. Kisamori, T. Kobayashi, D. Körper, S. Koyama, I. Kuti, V. Lapoux, S. Lindberg, F.M. Marqués, S. Masuoka, J. Mayer, K. Miki, T. Murakami, M.A. Najafi, K. Nakano, N. Nakatsuka, T. Nilsson, A. Obertelli, N.A. Orr, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, A. Revel, D. Rossi, A.T. Saito, T. Saito, M. Sasano, H. Sato, Y. Satou, H. Scheit, F. Schindler, P. Schrock, M. Shikata, Y. Shimizu, H. Simon, D. Sohler, O. Sorlin, L. Stuhl, S. Takeuchi, M. Tanaka, M. Thoennessen, H. Törnqvist, Y. Togano, T. Tomai, J. Tscheuschner, J. Tsubota, T. Uesaka, Z. Yang, and K. Yoneda

Subjects
In-beam γ-ray spectroscopy, Island of inversion, Shell evolution, Physics, QC1-999
Abstract

Detailed γ-ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for 28Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N=20 and N=28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Published
2023
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3. Low-lying single-particle structure of 17C and the N = 14 sub-shell closure

Author

X. Pereira-López, B. Fernández-Domínguez, F. Delaunay, N.L. Achouri, N.A. Orr, W.N. Catford, M. Assié, S. Bailey, B. Bastin, Y. Blumenfeld, R. Borcea, M. Caamaño, L. Caceres, E. Clément, A. Corsi, N. Curtis, Q. Deshayes, F. Farget, M. Fisichella, G. de France, S. Franchoo, M. Freer, J. Gibelin, A. Gillibert, G.F. Grinyer, F. Hammache, O. Kamalou, A. Knapton, T. Kokalova, V. Lapoux, J.A. Lay, B. Le Crom, S. Leblond, J. Lois-Fuentes, F.M. Marqués, A. Matta, P. Morfouace, A.M. Moro, T. Otsuka, J. Pancin, L. Perrot, J. Piot, E. Pollacco, D. Ramos, C. Rodríguez-Tajes, T. Roger, F. Rotaru, M. Sénoville, N. de Séréville, R. Smith, O. Sorlin, M. Stanoiu, I. Stefan, C. Stodel, D. Suzuki, T. Suzuki, J.C. Thomas, N. Timofeyuk, M. Vandebrouck, J. Walshe, and C. Wheldon

Subjects
Physics, QC1-999
Abstract

The first investigation of the single-particle structure of the bound states of 17C, via the d(16C,p) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1/2+ and 5/2+ for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N=14 sub-shell closure. The very small spectroscopic factor found for the 3/2+ ground state is consistent with theoretical predictions and indicates that the ν1d3/2 strength is carried by unbound states. With a dominant ℓ=0 valence neutron configuration and a very low separation energy, the 1/2+ excited state is a one-neutron halo candidate.

Published
2020
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4. Stopping power of fission fragments in thin Mylar and nickel foils

Author

Ulli Köster, Q. Deshayes, A. Letourneau, M. Kebbiri, T. Materna, E. Berthoumieux, D. Doré, L. Thulliez, X. Ledoux, Y.H. Kim, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Laue-Langevin (ILL), ILL, Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Fission, Nuclear and High Energy Physics, Energy loss, Physics - Instrumentation and Detectors, Materials science, Separator (oil production), chemistry.chemical_element, FOS: Physical sciences, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Stopping power, Kinetic energy, 01 natural sciences, Heavy ions, Ion, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Instrumentation, 010308 nuclear & particles physics, Instrumentation and Detectors (physics.ins-det), Nickel, Cardinal point, chemistry, Atomic physics
Abstract

The energy loss of heavy ions in thin Mylar and nickel foils was measured accurately using fission fragments from $^{239}Pu(n_{th},f)$, mass and energy separated by the Lohengrin separator at ILL. The detection setup, placed at the focal plane of the Lohengrin separator enabled to measure precisely the kinetic energy difference of selected fragments after passing through the sample. From these data, the stopping powers in Mylar and nickel layers were extracted and compared to calculations. Whereas large deviations are observed with SRIM-2013 for Mylar, fairly good agreements are obtained with the semi-empirical approach of Knyazheva et al. and the calculations contained within the DPASS database. In nickel, SRIM-2013 and Knyazheva model are in agreement with our data within about 10 %, while large deviations are observed with DPASS. We used our data to provide updated parameters for the Knyazheva et al. model and rescale DPASS database for nickel and Mylar., Comment: 19 pages, 18 figures

Published
2021
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5. Halo Structure of the Neutron-Dripline Nucleus B19

Author

K. J. Cook, T. Kobayashi, S. K. Kim, H. Baba, T. Motobayashi, T. Murakami, S. Leblond, Takashi Nakamura, Yosuke Kondo, Hiroyuki Takeda, Ryuki Tanaka, Julien Gibelin, Noritsugu Nakatsuka, Hideaki Otsu, D. Kameda, K. Yoneda, Satoshi Takeuchi, Toshiyuki Kubo, Y. Satou, Kazuyuki Ogata, T. Isobe, Thomas Aumann, N. L. Achouri, Atsumi Saito, Nagao Kobayashi, T. Nakashima, S. Nishi, J. Lee, D. Kanno, Kouichi Hagino, S. Ogoshi, Q. Deshayes, K. Takahashi, Yohei Shimizu, Yasuhiro Togano, Daichi Murai, A. G. Tuff, K. Muto, H. Suzuki, Marine Vandebrouck, Franck Delaunay, F. M. Marqués, H. Sato, P. Doornenbal, Jongwon Hwang, A. Navin, Naoki Fukuda, N. A. Orr, J. Tsubota, Naohito Inabe, and R. Minakata

Subjects
Physics, Valence (chemistry), Isotope, Nuclear Theory, General Physics and Astronomy, 01 natural sciences, Dipole, 0103 physical sciences, Coulomb, Neutron, Halo, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Excitation
Abstract

The heaviest bound isotope of boron ^{19}B has been investigated using exclusive measurements of its Coulomb dissociation, into ^{17}B and two neutrons, in collisions with Pb at 220 MeV/nucleon. Enhanced electric dipole (E1) strength is observed just above the two-neutron decay threshold with an integrated E1 strength of B(E1)=1.64±0.06(stat)±0.12(sys) e^{2} fm^{2} for relative energies below 6 MeV. This feature, known as a soft E1 excitation, provides the first firm evidence that ^{19}B has a prominent two-neutron halo. Three-body calculations that reproduce the energy spectrum indicate that the valence neutrons have a significant s-wave configuration and exhibit a dineutronlike correlation.

Published
2020
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6. Extending the Southern Shore of the Island of Inversion to F28

Author

J. Mayer, Noritsugu Nakatsuka, Michael Thoennessen, A. Gillibert, Ákos Horváth, Q. Deshayes, Yosuke Kondo, J. Tscheuschner, Nasser Kalantar-Nayestanaki, J. M. Gheller, István Kuti, M. Shikata, Thomas Aumann, C. Caesar, J. Tsubota, A. Revel, N. L. Achouri, W. He, Z. Elekes, Calem Hoffman, Shoichiro Kawase, Heiko Scheit, J. Kahlbow, Masahiro Yasuda, H. Simon, H. Sato, K. Yoneda, A. Horvat, K. Nakano, Igor Gašparić, T. Ozaki, H. Chae, J. A. Tostevin, L. Stuhl, K. Miki, F. de Oliveira Santos, H. L. Crawford, D. Calvet, Stefanos Paschalis, S. Masuoka, T. Isobe, A. Obertelli, Tomoki Saito, Momoko Tanaka, N. A. Orr, Shoko Koyama, Nobuyuki Chiga, L. Atar, Y. Satou, P. Fallon, Atsumi Saito, Zsolt Dombrádi, H. Törnqvist, Jongwon Hwang, A. Corsi, Julien Gibelin, K. Boretzky, A. Delbart, D. M. Rossi, H. Baba, Masaki Sasano, D. Sohler, V. Lapoux, M. A. Najafi, S. K. Kim, A. Hirayama, H. Al Falou, K. Kisamori, T. Tomai, V. Panin, P. Schrock, Takashi Nakamura, Yasuhiro Togano, M.N. Harakeh, M. Holl, Zaihong Yang, F. Nowacki, T. Kobayashi, Cenxi Yuan, D. Körper, Tomohiro Uesaka, Thomas Nilsson, C. A. Douma, Simon Lindberg, Hideaki Otsu, O. Sorlin, T. Murakami, Yohei Shimizu, Fabia Schindler, Franck Delaunay, F. M. Marqués, and Satoshi Takeuchi

Subjects
Physics, Proton, Island of inversion, General Physics and Astronomy, 01 natural sciences, Spectral line, Momentum, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, Nucleon, Spectroscopy, Ground state
Abstract

Detailed spectroscopy of the neutron-unbound nucleus 28 F has been performed for the first time following proton/neutron removal from 29 Ne / 29 F beams at energies around 230 MeV / nucleon . The invariant-mass spectra were reconstructed for both the 27 F ( * ) + n and 26 F ( * ) + 2 n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the 28 F ground state, with S n ( 28 F ) = − 199 ( 6 ) keV , while analysis of the 2 n decay channel allowed a considerably improved S n ( 27 F ) = 1620 ( 60 ) keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of 28 F . Importantly, in the case of the ground state, the reconstructed 27 F + n momentum distribution following neutron removal from 29 F indicates that it arises mainly from the 1 p 3 / 2 neutron intruder configuration. This demonstrates that the island of inversion around N = 20 includes 28 F , and most probably 29 F , and suggests that 28 O is not doubly magic.

Published
2020
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7. Lifetime measurement of the $^{26}0 g.s.$ at SAMURAI

Author

Hiroyuki Takeda, Takashi Nakamura, Hideaki Otsu, Olivier Sorlin, Masaki Sasano, Zaihong Yang, I. Murray, D. M. Rossi, Yuya Kubota, A. Hirayama, Thomas Aumann, Makoto Yasuda, K. I. Hahn, L. Atar, H. Baba, Sonja Storck, S. Choi, Z. Halász, Yohei Shimizu, C. Caesar, L. Stuhl, H. Scheit, C. Lehr, Nobuyuki Chiga, Yasuhiro Togano, Thomas Nilsson, Hans Törnqvist, Z. Elekes, D. Körper, M. Matsumoto, M. L. Cortés, Naohito Inabe, Yosuke Kondo, T. Murakami, D. S. Ahn, K. Yoneda, Marina Petri, Atsumi Saito, T. Tomai, Tomohiro Uesaka, M. Parlog, Simon Lindberg, V. Panin, M. Marques, D. Cortina-Gil, T. Isobe, H. Chae, S. K. Kim, István Kuti, Jongwon Hwang, Herbert A. Simon, P. Schrock, Naoki Fukuda, T. Kobayashi, J. Kahlbow, H. Suzuki, D. Sohler, H. Yamada, I. Syndikus, K. Boretzky, Q. Deshayes, P. Doornenbal, I. Gaparic, Stefanos Paschalis, Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), SAMURAI20, Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Physics, Superconductivity, History, Radionuclide, Spectrum analyzer, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 010305 fluids & plasmas, Computer Science Applications, Education, Nuclear physics, Stack (abstract data type), 0103 physical sciences, Physics::Accelerator Physics, ddc:530, Neutron, Radio isotopes, 010306 general physics, Ground state, Nuclear Experiment, Beam (structure)
Abstract

27th International Nuclear Physics Conference, INPC2019, Glasgow, United Kingdom, 29 Jul 2019 - 2 Aug 2019; Journal of physics / Conference series 1643(1), 012106 (2020). doi:10.1088/1742-6596/1643/1/012106, Published by IOP Publ., Bristol

Published
2020
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8. Extracting the spectral signature of α clustering in Ti44,48,52 using a continuous wavelet transform

Author

N. Curtis, Q. Deshayes, T. Kokalova, J. Walshe, Robin Smith, Neven Soić, Martin Freer, Asim Soylu, S. Bailey, L. Prepolec, V. Tokić, Lynda Achouri, Franck Delaunay, Marian Parlog, F. M. Marqués, Bertrand Jacquot, B. Fernández-Domínguez, and C. Wheldon

Subjects
Physics, Spectral signature, 010308 nuclear & particles physics, Nuclear state, Structure (category theory), Nuclear structure, 01 natural sciences, Resonant scattering, Computational physics, medicine.anatomical_structure, 0103 physical sciences, medicine, 010306 general physics, Cluster analysis, Nucleus, Continuous wavelet transform
Abstract

A novel technique has been developed, making use of the continuous wavelet transform to identify α-clustered states from resonant scattering measurements in regions of high nuclear state density. This technique expedites the investigation of α-clustering in medium mass and heavy nuclei, where the role that α-clustering plays in the structure of the nucleus is poorly understood. Here we report the application of this technique to measurements of the 4He(40,44,48Ca,α) resonant reactions, leading to an assessment of the α-cluster structure of 44,48,52Ti. Alpha-clustering was identified in 44Ti and 52Ti, but was observed to break down in 48Ti. The implications of these results are discussed.

Published
2019
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9. First Observation of B20 and B21

Author

T. Murakami, Tomio Kubo, Hiroshi Suzuki, Yosuke Kondo, Y. Shimizu, D. Kameda, K. Takahashi, Thomas Aumann, Q. Deshayes, Yasuhiro Togano, M Vandebrouck, P. Doornenbal, K. Muto, T. Isobe, T. Motobayashi, A. Navin, Hiroshi Sato, T. Kobayashi, Jongwon Hwang, S. K. Kim, J. Bonnard, N. A. Orr, D. Kanno, Hideaki Otsu, Y. Satou, A. G. Tuff, Naoki Fukuda, R. Minakata, Nagao Kobayashi, Julien Gibelin, Nicolas Michel, K. Yoneda, Franck Delaunay, Takashi Nakamura, F. M. Marqués, H. Baba, Ryuki Tanaka, S. Ogoshi, Satoshi Takeuchi, S. Nishi, N. L. Achouri, Noritsugu Nakatsuka, J.H. Lee, Daichi Murai, Naohito Inabe, H. Takeda, S. Leblond, and T. Nakashima

Subjects
Physics, education.field_of_study, Proton, 010308 nuclear & particles physics, Nuclear Theory, SHELL model, Population, General Physics and Astronomy, Resonance, Isotopes of boron, 01 natural sciences, 0103 physical sciences, Quark–gluon plasma, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, education
Abstract

The most neutron-rich boron isotopes ^{20}B and ^{21}B have been observed for the first time following proton removal from ^{22}N and ^{22}C at energies around 230 MeV/nucleon. Both nuclei were found to exist as resonances which were detected through their decay into ^{19}B and one or two neutrons. Two-proton removal from ^{22}N populated a prominent resonancelike structure in ^{20}B at around 2.5 MeV above the one-neutron decay threshold, which is interpreted as arising from the closely spaced 1^{-},2^{-} ground-state doublet predicted by the shell model. In the case of proton removal from ^{22}C, the ^{19}B plus one- and two-neutron channels were consistent with the population of a resonance in ^{21}B 2.47±0.19 MeV above the two-neutron decay threshold, which is found to exhibit direct two-neutron decay. The ground-state mass excesses determined for ^{20,21}B are found to be in agreement with mass surface extrapolations derived within the latest atomic-mass evaluations.

Published
2018
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10. Performance validation of the first arm of FALSTAFF: $^{252}$Cf and $^{235}$U fission fragment characterisation

Author

M. Kebbiri, Diane Doré, P. Legou, Michel Combet, A. Marcel, L. Thulliez, J-Ph. Mols, Q. Deshayes, S. Herlant, Stephan Oberstedt, E. Berthoumieux, X. Ledoux, M.O. Frégeau, J. Pancin, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Fission, Physics::Instrumentation and Detectors, QC1-999, Nuclear Theory, Nuclear data, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 7. Clean energy, Neutron temperature, Nuclear physics, Prompt neutron, Nuclear fission, 0103 physical sciences, Neutron, 010306 general physics, Nuclear Experiment, Spontaneous fission
Abstract

The renewed interest for the study of nuclear fission is mainly motivated by the development of GEN-IV reactor concepts, mostly foreseen to operate in the fast neutron energy domain. To support this development, new high-quality nuclear data are needed. In this context, a new experimental setup, the FALSTAFF spectrometer, dedicated to the study of nuclear fission is under development. Employing the double-velocity (2V) and energy-velocity (EV) methods, the fission fragment mass before and after neutron evaporation will be deduced and the correlation between prompt neutron multiplicity and fragment mass will be determined. The first arm of the spectrometer is achieved. It is composed of two SED-MWPC detectors (a combination of a foil to produce secondary electrons and a Multi-Wire Proportional Chamber to detect them) and an axial ionization chamber. The SED-MWPC give access to the velocity (V) via time-of-flight and position measurements. The ionization chamber measures the fragment kinetic energy (E) and the energy loss profile. Preliminary results for spontaneous fission of 252Cf and from the thermal-neutron induced fission experiment on 235U, performed at the Orphée reactor (CEA-Saclay, France), are presented.

Published
2018
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11. Reaction Cross Section Of The Two-neutron Halo Nucleus 22C At 235 MeV/nucleon

Author

T. Isobe, D. Kanno, Shuichi Takeuchi, Jongwon Hwang, Marine Vandebrouck, Y. Shimizu, N. A. Orr, J.H. Lee, Yasuhiro Togano, A. G. Tuff, S. Leblond, T. Nakashima, K. Yoneda, Franck Delaunay, F. M. Marqués, S. Nishi, S. Ogoshi, H. Takeda, T. Murakami, S. K. Kim, Hiroshi Sato, T. Kobayashi, Hideaki Otsu, D. Kameda, P. Doornenbal, Naoki Fukuda, K. Takahashi, Q. Deshayes, K. Muto, N. Kobayashi, Atsumi Saito, T. Motobayashi, Julien Gibelin, H. Baba, Ryuki Tanaka, Terutaro Nakamura, H. Suzuki, R. Minakata, Noritsugu Nakatsuka, Daichi Murai, Yosuke Kondo, J. Tsubota, N. L. Achouri, J. A. Tostevin, A. Navin, Naohito Inabe, Yo Sato, Thomas Aumann, Tomio Kubo, Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)

Subjects
Physics, Nuclear physics, Isotope, Sigma, Halo nucleus, Neutron, Radius, Halo, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nucleon, 7. Clean energy, Glauber
Abstract

The reaction cross section (σ R σR ) of the very neutron-rich carbon isotope 22 22 C has been measured on a carbon target at 235 MeV/nucleon. A σ R σR of 1.280±0.023 1.280±0.023 b was obtained for 22 22 C, significantly larger than those for the neighboring isotopes, supporting the halo character of 22 22 C. A 22 22 C root-mean-squared matter radius of 3.44±0.08 3.44±0.08 fm was deduced using a four-body Glauber reaction model. This value is smaller than an earlier estimate of 5.4±0.9 5.4±0.9 fm derived from a σ R σR measurement on a hydrogen target at 40 MeV/nucleon.

Published
2016
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12. Magicity versus Superfluidity around ^{28}O viewed from the Study of ^{30}F.

Author

Kahlbow J, Aumann T, Sorlin O, Kondo Y, Nakamura T, Nowacki F, Revel A, Achouri NL, Al Falou H, Atar L, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Elekes Z, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Harakeh MN, Hirayama A, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Orr NA, Otsu H, Ozaki T, Panin V, Paschalis S, Rossi DM, Saito AT, Saito T, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimada K, Shimizu Y, Simon H, Sohler D, Stuhl L, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Uesaka T, Wang H, Yang Z, Yasuda M, and Yoneda K

Abstract

The neutron-rich unbound fluorine isotope ^{30}F_{21} has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasifree proton knockout reaction of ^{31}Ne nuclei at 235  MeV/nucleon. The mass and thus one-neutron-separation energy of ^{30}F has been determined to be S_{n}=-472±58(stat)±33(sys)  keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in S_{n}(^{30}F) shows that the "magic" N=20 shell gap is not restored close to ^{28}O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron d and fp orbitals, with the 1p_{3/2} and 1p_{1/2} orbitals becoming more bound than the 0f_{7/2} one. This degeneracy and reordering of orbitals has two potential consequences: ^{28}O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both ^{29,31}F appear to be good two-neutron halo-nucleus candidates.

Published
2024
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13. Publisher Correction: First observation of 28 O.

Author

Kondo Y, Achouri NL, Falou HA, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Ekström A, Elekes Z, Forssén C, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Hagen G, Harakeh MN, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Jiang WG, Kahlbow J, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakamura T, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Ogata K, de Oliveira Santos F, Orr NA, Otsu H, Otsuka T, Ozaki T, Panin V, Papenbrock T, Paschalis S, Revel A, Rossi D, Saito AT, Saito TY, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu N, Shimizu Y, Simon H, Sohler D, Sorlin O, Stuhl L, Sun ZH, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Tsunoda N, Uesaka T, Utsuno Y, Vernon I, Wang H, Yang Z, Yasuda M, Yoneda K, and Yoshida S

Published
2023
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14. First observation of 28 O.

Author

Kondo Y, Achouri NL, Falou HA, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Ekström A, Elekes Z, Forssén C, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Hagen G, Harakeh MN, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Jiang WG, Kahlbow J, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakamura T, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Ogata K, de Oliveira Santos F, Orr NA, Otsu H, Otsuka T, Ozaki T, Panin V, Papenbrock T, Paschalis S, Revel A, Rossi D, Saito AT, Saito TY, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu N, Shimizu Y, Simon H, Sohler D, Sorlin O, Stuhl L, Sun ZH, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Tsunoda N, Uesaka T, Utsuno Y, Vernon I, Wang H, Yang Z, Yasuda M, Yoneda K, and Yoshida S

Abstract

Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10 -21  s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of 28 O and 27 O through their decay into 24 O and four and three neutrons, respectively. The 28 O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers 1,2 , it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called 'doubly magic' nuclei. Both 27 O and 28 O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28 O from a 29 F beam is consistent with it not exhibiting a closed N = 20 shell structure., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2023
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15. Halo Structure of the Neutron-Dripline Nucleus ^{19}B.

Author

Cook KJ, Nakamura T, Kondo Y, Hagino K, Ogata K, Saito AT, Achouri NL, Aumann T, Baba H, Delaunay F, Deshayes Q, Doornenbal P, Fukuda N, Gibelin J, Hwang JW, Inabe N, Isobe T, Kameda D, Kanno D, Kim S, Kobayashi N, Kobayashi T, Kubo T, Leblond S, Lee J, Marqués FM, Minakata R, Motobayashi T, Muto K, Murakami T, Murai D, Nakashima T, Nakatsuka N, Navin A, Nishi S, Ogoshi S, Orr NA, Otsu H, Sato H, Satou Y, Shimizu Y, Suzuki H, Takahashi K, Takeda H, Takeuchi S, Tanaka R, Togano Y, Tsubota J, Tuff AG, Vandebrouck M, and Yoneda K

Abstract

The heaviest bound isotope of boron ^{19}B has been investigated using exclusive measurements of its Coulomb dissociation, into ^{17}B and two neutrons, in collisions with Pb at 220  MeV/nucleon. Enhanced electric dipole (E1) strength is observed just above the two-neutron decay threshold with an integrated E1 strength of B(E1)=1.64±0.06(stat)±0.12(sys)  e^{2} fm^{2} for relative energies below 6 MeV. This feature, known as a soft E1 excitation, provides the first firm evidence that ^{19}B has a prominent two-neutron halo. Three-body calculations that reproduce the energy spectrum indicate that the valence neutrons have a significant s-wave configuration and exhibit a dineutronlike correlation.

Published
2020
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16. Extending the Southern Shore of the Island of Inversion to ^{28}F.

Author

Revel A, Sorlin O, Marqués FM, Kondo Y, Kahlbow J, Nakamura T, Orr NA, Nowacki F, Tostevin JA, Yuan CX, Achouri NL, Al Falou H, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Crawford HL, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Elekes Z, Fallon P, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Harakeh MN, He W, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, de Oliveira Santos F, Otsu H, Ozaki T, Panin V, Paschalis S, Rossi D, Saito AT, Saito T, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu Y, Simon H, Sohler D, Stuhl L, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Uesaka T, Yang Z, Yasuda M, and Yoneda K

Abstract

Detailed spectroscopy of the neutron-unbound nucleus ^{28}F has been performed for the first time following proton/neutron removal from ^{29}Ne/^{29}F beams at energies around 230  MeV/nucleon. The invariant-mass spectra were reconstructed for both the ^{27}F^{(*)}+n and ^{26}F^{(*)}+2n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the ^{28}F ground state, with S_{n}(^{28}F)=-199(6)  keV, while analysis of the 2n decay channel allowed a considerably improved S_{n}(^{27}F)=1620(60)  keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of ^{28}F. Importantly, in the case of the ground state, the reconstructed ^{27}F+n momentum distribution following neutron removal from ^{29}F indicates that it arises mainly from the 1p_{3/2} neutron intruder configuration. This demonstrates that the island of inversion around N=20 includes ^{28}F, and most probably ^{29}F, and suggests that ^{28}O is not doubly magic.

Published
2020
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17. First Observation of ^{20}B and ^{21}B.

Author

Leblond S, Marqués FM, Gibelin J, Orr NA, Kondo Y, Nakamura T, Bonnard J, Michel N, Achouri NL, Aumann T, Baba H, Delaunay F, Deshayes Q, Doornenbal P, Fukuda N, Hwang JW, Inabe N, Isobe T, Kameda D, Kanno D, Kim S, Kobayashi N, Kobayashi T, Kubo T, Lee J, Minakata R, Motobayashi T, Murai D, Murakami T, Muto K, Nakashima T, Nakatsuka N, Navin A, Nishi S, Ogoshi S, Otsu H, Sato H, Satou Y, Shimizu Y, Suzuki H, Takahashi K, Takeda H, Takeuchi S, Tanaka R, Togano Y, Tuff AG, Vandebrouck M, and Yoneda K

Abstract

The most neutron-rich boron isotopes ^{20}B and ^{21}B have been observed for the first time following proton removal from ^{22}N and ^{22}C at energies around 230  MeV/nucleon. Both nuclei were found to exist as resonances which were detected through their decay into ^{19}B and one or two neutrons. Two-proton removal from ^{22}N populated a prominent resonancelike structure in ^{20}B at around 2.5 MeV above the one-neutron decay threshold, which is interpreted as arising from the closely spaced 1^{-},2^{-} ground-state doublet predicted by the shell model. In the case of proton removal from ^{22}C, the ^{19}B plus one- and two-neutron channels were consistent with the population of a resonance in ^{21}B 2.47±0.19  MeV above the two-neutron decay threshold, which is found to exhibit direct two-neutron decay. The ground-state mass excesses determined for ^{20,21}B are found to be in agreement with mass surface extrapolations derived within the latest atomic-mass evaluations.

Published
2018
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