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1. Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes

Author: P.J. Li, J. Lee, P. Doornenbal, S. Chen, S. Wang, A. Obertelli, Y. Chazono, J.D. Holt, B.S. Hu, K. Ogata, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, K. Boretzky, C. Caesar, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, J. Kahlbow, D. Kim, T. Koiwai, Y. Kondo, D. Körper, P. Koseoglou, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Miki, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, F. Schindler, H. Simon, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, J. Tscheuschner, V. Vaquero, V. Wagner, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Unbound states, Knockout reaction, Single-particle strength, Shell evolution, Physics, QC1-999
Abstract: The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p,pn) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41)keV in 53Ca and 6000(250)keV in 55Ca indicate a significant l =3 component, providing the first experimental evidence for the ν0f7/2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν0f7/2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z=28.
Published: 2024
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2. Level structures of 56,58Ca cast doubt on a doubly magic 60Ca

Author: S. Chen, F. Browne, P. Doornenbal, J. Lee, A. Obertelli, Y. Tsunoda, T. Otsuka, Y. Chazono, G. Hagen, J.D. Holt, G.R. Jansen, K. Ogata, N. Shimizu, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, D. Calvet, F. Château, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Shell evolution, γ Ray spectroscopy, Physics, QC1-999
Abstract: Gamma decays were observed in 56Ca and 58Ca following quasi-free one-proton knockout reactions from 57,59Sc beams at ≈200 MeV/nucleon. For 56Ca, a γ ray transition was measured to be 1456(12) keV, while for 58Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the 21+→0gs+ decays, and were compared to results from ab initio and conventional shell-model approaches. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for 21+ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N = 34 shell. Its constituents, the 0f5/2 and 0g9/2 orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic 60Ca and potentially drives the dripline of Ca isotopes to 70Ca or even beyond.
Published: 2023
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3. The β-decay of 70Kr into 70Br: Restoration of the pseudo-SU(4) symmetry

Author: A. Vitéz-Sveiczer, A. Algora, A.I. Morales, B. Rubio, G.G. Kiss, P. Sarriguren, P. Van Isacker, G. de Angelis, F. Recchia, S. Nishimura, J. Agramunt, V. Guadilla, A. Montaner-Pizá, S.E.A. Orrigo, A. Horváth, D. Napoli, S. Lenzi, A. Boso, V.H. Phong, J. Wu, P.-A. Söderström, T. Sumikama, H. Suzuki, H. Takeda, D.S. Ahn, H. Baba, P. Doornebal, N. Fukuda, N. Inabe, T. Isobe, T. Kubo, S. Kubono, H. Sakurai, Y. Shimizu, C. Sidong, B. Blank, P. Ascher, M. Gerbaux, T. Goigoux, J. Giovinazzo, S. Grévy, T. Kurtukián Nieto, C. Magron, W. Gelletly, Zs. Dombrádi, Y. Fujita, M. Tanaka, P. Aguilera, F. Molina, J. Eberth, F. Diel, D. Lubos, C. Borcea, E. Ganioglu, D. Nishimura, H. Oikawa, Y. Takei, S. Yagi, W. Korten, G. de France, P. Davies, J. Liu, J. Lee, T. Lokotko, I. Kojouharov, N. Kurz, H. Shaffner, and A. Petrovici
Subjects: Beta decay of 70Kr, pn pairing, GT strength distribution, Pseudo-SU(4) symmetry, QRPA calculations, Physics, QC1-999
Abstract: The β-decay of the even-even nucleus 70Kr with Z=N+2, has been investigated at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center using the BigRIPS fragment separator, the ZeroDegree Spectrometer, the WAS3ABI implantation station and the EURICA HPGe cluster array. Fifteen γ-rays associated with the β-decay of 70Kr into 70Br have been identified for the first time, defining ten populated states below Eexc=3300 keV. The half-life of 70Kr was derived with increased precision and found to be t1/2=45.19±0.14 ms. The β-delayed proton emission probability has also been determined as εp=0.545(23)%. An increase in the β-strength to the yrast 1+ state in comparison with the heaviest Z=N+2 system studied so far (62Ge decay) is observed that may indicate increased np correlations in the T=0 channel. The β-decay strength deduced from the results is interpreted in terms of the proton-neutron quasiparticle random-phase approximation (pnQRPA) and also with a schematic model that includes isoscalar and isovector pairing in addition to quadrupole deformation. The application of this last model indicates an approximate realization of pseudo-SU(4) symmetry in this system.
Published: 2022
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4. A first glimpse at the shell structure beyond 54Ca: Spectroscopy of 55K, 55Ca, and 57Ca

Author: T. Koiwai, K. Wimmer, P. Doornenbal, A. Obertelli, C. Barbieri, T. Duguet, J.D. Holt, T. Miyagi, P. Navrátil, K. Ogata, N. Shimizu, V. Somà, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Radioactive beams, γ-ray spectroscopy, Shell evolution, Physics, QC1-999
Abstract: States in the N=35 and 37 isotopes 55,57Ca have been populated by direct proton-induced nucleon removal reactions from 56,58Sc and 56Ca beams at the RIBF. In addition, the (p,2p) quasi-free single-proton removal reaction from 56Ca was studied. Excited states in 55K, 55Ca, and 57Ca were established for the first time via in-beam γ-ray spectroscopy. Results for the proton and neutron removal reactions from 56Ca to states in 55K and 55Ca for the level energies, excited state lifetimes, and exclusive cross sections agree well with state-of-the-art theoretical calculations using different approaches. The observation of a short-lived state in 57Ca suggests a transition in the calcium isotopic chain from single-particle dominated states at N=35 to collective excitations at N=37.
Published: 2022
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5. Inclusive cross sections for one- and multi-nucleon removal from Sn, Sb, and Te projectiles beyond the N = 82 shell closure

Author: V. Vaquero, A. Jungclaus, J.L. Rodríguez-Sánchez, J.A. Tostevin, P. Doornenbal, K. Wimmer, S. Chen, E. Nácher, E. Sahin, Y. Shiga, D. Steppenbeck, R. Taniuchi, Z.Y. Xu, T. Ando, H. Baba, F.L. Bello Garrote, S. Franchoo, A. Gargano, K. Hadynska-Klek, A. Kusoglu, J. Liu, T. Lokotko, S. Momiyama, T. Motobayashi, S. Nagamine, N. Nakatsuka, M. Niikura, R. Orlandi, T. Saito, H. Sakurai, P.A. Söderström, G.M. Tveten, Zs. Vajta, and M. Yalcinkaya
Subjects: Physics, QC1-999
Abstract: Inclusive one- and multi-nucleon removal cross sections have been measured for several Sn, Sb and Te isotopes just beyond the N=82 neutron shell closure. The beams were produced in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. The experimental cross sections are compared to predictions from the most recent version of the Liege intranuclear cascade model. Although the overall agreement is good, severe discrepancies are observed for the cases of one- and two-neutron removal from 134Sn and 135Sb projectiles and one-proton knockout from all measured N=84 isotones. These discrepancies, as well as the relevance of quasi-elastic reaction channels to the one-neutron removal cross sections, are discussed. In addition, the measured inclusive one-proton knockout cross section for the semi-magic 134Sn projectile is compared to eikonal direct reaction theory calculations to assess if the suppression factors to these calculated cross sections, deduced from data on reactions of lighter projectile nuclei, are also applicable to heavy nuclei. Keywords: Inclusive knockout cross sections, Intranuclear cascade model, Eikonal reaction theory
Published: 2019
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6. First spectroscopic study of 51Ar by the (p,2p) reaction

Author: M.M. Juhász, Z. Elekes, D. Sohler, Y. Utsuno, K. Yoshida, T. Otsuka, K. Ogata, P. Doornenbal, A. Obertelli, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, N.L. Achouri, O. Aktas, T. Aumann, L.X. Chung, Zs. Dombrádi, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, H.N. Liu, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Proton knock-out reaction, γ-ray spectroscopy, Invariant mass method, Nuclear structure, Shell closure, Physics, QC1-999
Abstract: The nuclear structure of 51Ar, an uncharted territory so far, was studied by the (p,2p) reaction using γ-ray spectroscopy for the bound states and the invariant mass method for the unbound states. Two peaks were detected in the γ-ray spectrum and six peaks were observed in the 50Ar+n relative energy spectrum. Comparing the results to our shell-model calculations, two bound and six unbound states were established. Three of the unbound states could only be placed tentatively due to the low number of counts in the relative energy spectrum of events associated with the decay through the first excited state of 50Ar. The low cross sections populating the two bound states of 51Ar could be interpreted as a clear signature for the presence of significant subshell closures at neutron numbers 32 and 34 in argon isotopes. It was also revealed that due to the two valence holes, unbound collective states coexist with individual-particle states in 51Ar.
Published: 2021
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7. Restoration of the natural E(1/21+) - E(3/21+) energy splitting in odd-K isotopes towards N = 40

Author: Y.L. Sun, A. Obertelli, P. Doornenbal, C. Barbieri, Y. Chazono, T. Duguet, H.N. Liu, P. Navrátil, F. Nowacki, K. Ogata, T. Otsuka, F. Raimondi, V. Somà, Y. Utsuno, K. Yoshida, N. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, D. Sohler, P.-A. Söderström, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Physics, QC1-999
Abstract: We report on the first γ-ray spectroscopy of 51,53K produced via the 52,54Ca(p,2p) reactions at ∼250 MeV/nucleon. Unambiguous final-state angular-momentum assignments were achieved for beam intensities down to few particles per second by using a new technique based on reaction vertex tracking combined with a thick liquid-hydrogen target. Through γ-ray spectroscopy and exclusive parallel momentum distribution analysis, 3/2+ ground states and 1/2+ first excited states in 51,53K were established quantifying the natural ordering of the 1d3/2 and 2s1/2 proton-hole states that are restored at N = 32 and 34. State-of-the-art ab initio calculations and shell-model calculations with improved phenomenological effective interactions reproduce the present data and predict consistently the increase of the E(1/21+) - E(3/21+) energy differences towards N = 40. Keywords: Spectroscopy, Shell evolution, 51K, 53K
Published: 2020
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8. Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti

Author: M.L. Cortés, W. Rodriguez, P. Doornenbal, A. Obertelli, J.D. Holt, S.M. Lenzi, J. Menéndez, F. Nowacki, K. Ogata, A. Poves, T.R. Rodríguez, A. Schwenk, J. Simonis, S.R. Stroberg, K. Yoshida, L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, D. Sohler, P.-A. Söderström, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: Physics, QC1-999
Abstract: Excited states in the N=40 isotone 62Ti were populated via the 63V(p,2p)62Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using γ-ray spectroscopy. The energies of the 21+→0gs+ and 41+→21+ transitions, observed here for the first time, indicate a deformed 62Ti ground state. These energies are increased compared to the neighboring 64Cr and 66Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for 62Ti show a dominant configuration with four neutrons excited across the N=40 gap. Likewise, they indicate that the N=40 island of inversion extends down to Z=20, disfavoring a possible doubly magic character of the elusive 60Ca. Keywords: Shell evolution, Radioactive beams, Gamma-ray spectroscopy
Published: 2020
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9. Multiple Mechanisms in Proton-Induced Nucleon Removal at ∼100 MeV/Nucleon

Author: T. Pohl, Y. L. Sun, A. Obertelli, J. Lee, M. Gómez-Ramos, K. Ogata, K. Yoshida, B. S. Cai, C. X. Yuan, B. A. Brown, H. Baba, D. Beaumel, A. Corsi, J. Gao, J. Gibelin, A. Gillibert, K. I. Hahn, T. Isobe, D. Kim, Y. Kondo, T. Kobayashi, Y. Kubota, P. Li, P. Liang, H. N. Liu, J. Liu, T. Lokotko, F. M. Marqués, Y. Matsuda, T. Motobayashi, T. Nakamura, N. A. Orr, H. Otsu, V. Panin, S. Y. Park, S. Sakaguchi, M. Sasano, H. Sato, H. Sakurai, Y. Shimizu, A. I. Stefanescu, L. Stuhl, D. Suzuki, Y. Togano, D. Tudor, T. Uesaka, H. Wang, X. Xu, Z. H. Yang, K. Yoneda, and J. Zenihiro
Subjects: General Physics and Astronomy
Published: 2023
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10. Extended p3/2 Neutron Orbital and the N=32 Shell Closure in Ca52

Author: M. Enciu, H. N. Liu, A. Obertelli, P. Doornenbal, F. Nowacki, K. Ogata, A. Poves, K. Yoshida, N. L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M. L. Cortés, A. Delbart, J-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L. X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, P. J. Li, B. D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti
Subjects: General Physics and Astronomy
Published: 2022
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11. 94 β -Decay Half-Lives of Neutron-Rich Cs55 to Ho67 : Experimental Feedback and Evaluation of the r -Process Rare-Earth Peak Formation

Author: J. Wu, S. Nishimura, G. Lorusso, P. Möller, E. Ideguchi, P.-H. Regan, G. S. Simpson, P.-A. Söderström, P. M. Walker, H. Watanabe, Z. Y. Xu, H. Baba, F. Browne, R. Daido, P. Doornenbal, Y. F. Fang, N. Fukuda, G. Gey, T. Isobe, Z. Korkulu, P. S. Lee, J. J. Liu, Z. Li, Z. Patel, V. Phong, S. Rice, H. Sakurai, L. Sinclair, T. Sumikama, M. Tanaka, A. Yagi, Y. L. Ye, R. Yokoyama, G. X. Zhang, D. S. Ahn, T. Alharbi, N. Aoi, F. L. Bello Garrote, G. Benzoni, A. M. Bruce, R. J. Carroll, K. Y. Chae, Z. Dombradi, A. Estrade, A. Gottardo, C. J. Griffin, N. Inabe, D. Kameda, H. Kanaoka, I. Kojouharov, F. G. Kondev, T. Kubo, S. Kubono, N. Kurz, I. Kuti, S. Lalkovski, G. J. Lane, E. J. Lee, T. Lokotko, G. Lotay, C.-B. Moon, D. Murai, H. Nishibata, I. Nishizuka, C. R. Nita, A. Odahara, Zs. Podolyák, O. J. Roberts, H. Schaffner, C. Shand, Y. Shimizu, H. Suzuki, H. Takeda, J. Taprogge, S. Terashima, Z. Vajta, and S. Yoshida
Published: 2017
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12. Investigation of the ground-state spin inversion in the neutron-rich Cl47,49 isotopes

Author: Jason D. Holt, Carlo Barbieri, Zaihong Yang, I. Murray, D. M. Rossi, K. I. Hahn, S. Y. Park, C. Hilaire, Kazuyuki Ogata, C. Lehr, H. Baba, Duo Yan, David Steppenbeck, H. Törnqvist, P. Koseoglou, Masahiro Yasuda, V. Lapoux, Yasuhiro Togano, N. L. Achouri, R.-B. Gerst, Alessandra Corsi, T. Lokotko, B. D. Linh, L. Stuhl, H. Wang, Dóra Sohler, M. Gómez-Ramos, Igor Gašparić, H. N. Liu, Y. L. Sun, Takashi Nakamura, E. Sahin, Petr Navrátil, V. Panin, W. Rodriguez, N. Shimizu, J. M. Gheller, A. Moro, Victor Vaquero, L. X. Chung, Thomas Duguet, K. Moschner, Hiroyoshi Sakurai, Kathrin Wimmer, Dong-Wook Kim, A. Delbart, N. T. Khai, V. Wagner, N. Paul, P. Doornenbal, T. Motobayashi, V. Somà, D. Calvet, T. Isobe, K. Yoneda, O. Aktas, V. Werner, Y. Yamada, Thomas Aumann, F. Flavigny, N. D. Ton, T. Kobayashi, A. Giganon, X. X. Xu, F. Château, Hideaki Otsu, Julien Gibelin, Si-Ge Chen, N. T. T. Phuc, P. A. Söderström, A. Gillibert, Nobuyuki Chiga, A. Obertelli, T. Koiwai, Tomohiro Uesaka, F. Browne, M. MacCormick, Satoshi Takeuchi, M. L. Cortés, Masaki Sasano, S. Franchoo, Yutaka Utsuno, Jenny Lee, Yuya Kubota, L. Zanetti, and Yosuke Kondo
Subjects: Physics, Isotope, 010308 nuclear & particles physics, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, Spin (physics), Ground state, 01 natural sciences, Inversion (discrete mathematics), Nuclear theory
Published: 2021
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13. Spectroscopy of Cd98 by two-nucleon removal from In100

Author: Joochun Park, Cenxi Yuan, K. Wimmer, F. Browne, I. Zanon, S. T. Wang, Luis Sarmiento Pico, Sidong Chen, P Liang, T. Lokotko, Alessandra Corsi, Ryo Taniuchi, Zhengtai Liu, K. Kokubun, T. Koiwa, Jenny Lee, D. Brugnara, Hiroyoshi Sakurai, Joakim Cederkäll, P. Doornenbal, Jinjia Liu, Sun Zhipeng, W. Xian, P. Li, Shan Jin, J. Gerl, G. Häfner, Shigeru Kubono, Alejandro Algora, M. L. Cortés, M. Górska, and P. Koseoglou
Subjects: Physics, Proton, 010308 nuclear & particles physics, Space (mathematics), 01 natural sciences, 7. Clean energy, Atomic orbital, Yield (chemistry), 0103 physical sciences, Level structure, Atomic physics, 010306 general physics, Spectroscopy, Nucleon, Excitation
Abstract: Low-lying states of Cd-98 have been populated by the two-nucleon removal reaction (In-100, Cd-98+gamma) and studied using in-beam gamma-ray spectroscopy at the Radioactive Isotope Beam Factory at RIKEN. Two new gamma transitions were identified and assigned as decays from a previously unknown state. This state is suggested to be based on a pi 1g(/9/2)(-1)2p(1/2)(-2) configuration with J(pi) = 5(-). The present observation extends the systematics of the excitation energies of the first 5(-) state in N = 50 isotones toward Sn-100. The determined energy of the 5(- )state in Cd-98 continues a smooth trend along the N = 50 isotones. The systematics are compared with shell-model calculations in different model spaces. Good agreement is achieved when considering a model space consisting of the pi(1f(5/2), 2p(3/2), 2p(1/2), 1g(9/2)) orbitals. The calculations with a smaller model space omitting the orbitals below the Z = 38 subshell could not reproduce the experimental energy difference between the ground and first 5(-) states in N = 50 isotones, because proton excitations across Z = 38 subshell yield a large amount of correlation energy that lowers the ground states. (Less)
Published: 2021
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14. Inclusive cross sections for one- and multi-nucleon removal from Sn, Sb, and Te projectiles beyond the N = 82 shell closure

Author: Hiroyoshi Sakurai, Megumi Niikura, F. L. Bello Garrote, Gry Merete Tveten, S. Franchoo, Yoshiaki Shiga, David Steppenbeck, Zs. Vajta, A. Jungclaus, M. Yalcinkaya, Pieter Doornenbal, K. Hadynska-Klek, JJ Liu, R. Orlandi, Hidetada Baba, S. Nagamine, Ryo Taniuchi, Enrique Nácher, Nathan Nakatsuka, Victor Vaquero, E. Sahin, Kathrin Wimmer, A. Kusoglu, J. A. Tostevin, A. Gargano, T. Lokotko, Toshiaki Ando, Si-Ge Chen, P. A. Söderström, Tohru Motobayashi, Zhengyu Xu, T. Saito, J. L. Rodriguez-Sanchez, Satoru Momiyama, RIKEN Nishina Center for Accelerator-Based Science, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Science and Technology Facilities Council (UK), Japan Society for the Promotion of Science, Research Council of Norway, SCOAP, 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), 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 and High Energy Physics, Isotope, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], 010308 nuclear & particles physics, Fission, Projectile, Nuclear Theory, Shell (structure), 01 natural sciences, lcsh:QC1-999, Nuclear physics, Cross section (physics), Inclusive knockout cross sections, 13. Climate action, 0103 physical sciences, Neutron, 010306 general physics, Nucleon, Eikonal reaction theory, Nuclear Experiment, Beam (structure), lcsh:Physics, Intranuclear cascade model
Abstract: 6 pags., 4 figs., 1 tab.-- Open Access funded by Creative Commons Atribution Licence 4.0, Inclusive one- and multi-nucleon removal cross sections have been measured for several Sn, Sb and Te isotopes just beyond the N=82 neutron shell closure. The beams were produced in the projectile fission of a U beam at the Radioactive Isotope Beam Factory at RIKEN. The experimental cross sections are compared to predictions from the most recent version of the Liege intranuclear cascade model. Although the overall agreement is good, severe discrepancies are observed for the cases of one- and two-neutron removal from Sn and Sb projectiles and one-proton knockout from all measured N=84 isotones. These discrepancies, as well as the relevance of quasi-elastic reaction channels to the one-neutron removal cross sections, are discussed. In addition, the measured inclusive one-proton knockout cross section for the semi-magic Sn projectile is compared to eikonal direct reaction theory calculations to assess if the suppression factors to these calculated cross sections, deduced from data on reactions of lighter projectile nuclei, are also applicable to heavy nuclei., We thank the staff of the RIKEN Nishina Center accelerator complex for providing high-intensity beams to the experiment. This work was supported by the Spanish Ministerio de Economía y Competitividad under contracts FPA2014-57196-C5-4-P and FPA2017-84756-C4-2-P. J.A.T. acknowledges the support of the Science and Technology Facilities Council (UK) grant ST/L005314/1 and R.O. that of JSPS KAKENHI Grant No. 26887048. G.M.T. grate-fully acknowledges funding of this research from the Research Council of Norway, Project Grant No. 222287.
Published: 2019
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15. Pairing Forces Govern Population of Doubly Magic Ca54 from Direct Reactions

Author: J. M. Gheller, S. Y. Park, K. Yoneda, Masaki Sasano, P. A. Söderström, D. Sohler, D. Körper, H. Simon, A. Gillibert, K. Miki, Satoshi Takeuchi, Yasuhiro Togano, M. MacCormick, R.-B. Gerst, Duo Yan, Tomohiro Uesaka, Fabia Schindler, V. Wagner, B. D. Linh, M. Holl, A. Corsi, N. Paul, Igor Gašparić, H. N. Liu, P. Koseoglou, E. Sahin, Yosuke Kondo, T. Lokotko, T. Isobe, Victor Vaquero, M. L. Cortés, V. Werner, Takashi Nakamura, W. Rodriguez, Zaihong Yang, A. Delbart, S. Franchoo, F. Château, V. Lapoux, P. Doornenbal, K. I. Hahn, L. Stuhl, I. Murray, C. Caesar, Kazuyuki Ogata, C. Lehr, T. Kobayashi, X. X. Xu, C. Hilaire, Si-Ge Chen, Yutaka Utsuno, V. Panin, A. Giganon, Jenny Lee, N. L. Achouri, L. X. Chung, Y. L. Sun, K. Moschner, Yuya Kubota, D. M. Rossi, H. Baba, F. Flavigny, Masahiro Yasuda, L. Zanetti, Kathrin Wimmer, Dong-Wook Kim, O. Aktas, F. Browne, S. Wang, A. Obertelli, J. Kahlbow, Hiroyoshi Sakurai, T. Motobayashi, Julien Gibelin, K. Boretzky, D. Calvet, David Steppenbeck, H. Törnqvist, Thomas Aumann, Nobuyuki Chiga, T. Koiwai, Kazuki Yoshida, Hideaki Otsu, Hirofumi Yamada, and J. Tscheuschner
Subjects: Physics, education.field_of_study, Proton, 010308 nuclear & particles physics, Nuclear Theory, Population, Nuclear shell model, General Physics and Astronomy, 01 natural sciences, 7. Clean energy, Pairing, Excited state, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Ground state, education
Abstract: Direct proton-knockout reactions of ^{55}Sc at ∼220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of ^{54}Ca were investigated through γ-ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological internucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the ^{55}Sc ground state with states in ^{54}Ca. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of ^{55}Sc, valence proton removals populated predominantly the ground state of ^{54}Ca. This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
Published: 2021
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16. First spectroscopic study of V63 at the N=40 island of inversion

Author: K. Moschner, David Steppenbeck, F. Browne, Jenny Lee, H. Törnqvist, Y. L. Sun, Kathrin Wimmer, Yuya Kubota, A. Gillibert, V. Panin, E. Sahin, L. X. Chung, D. Calvet, T. Isobe, Alessandra Corsi, Dóra Sohler, R.-B. Gerst, M. MacCormick, Yosuke Kondo, F. Château, Hideaki Otsu, P. Doornenbal, Hirofumi Yamada, N. Paul, V. Werner, Satoshi Takeuchi, M. L. Cortés, Masahiro Yasuda, D. M. Rossi, S. Franchoo, C. Lehr, W. Rodriguez, H. Baba, S. Y. Park, Z. Elekes, A. Giganon, Kazuyuki Ogata, Nobuyuki Chiga, Duo Yan, T. Lokotko, L. Zanetti, L. Stuhl, K. Yoneda, T. Koiwai, Takashi Nakamura, A. Delbart, Masaki Sasano, N. L. Achouri, S. Wang, B. D. Linh, Igor Gašparić, H. N. Liu, Yasuhiro Togano, V. Wagner, P. Koseoglou, F. Flavigny, J. M. Gheller, Tomohiro Uesaka, A. Obertelli, Zs. Dombrádi, Hiroyoshi Sakurai, T. Motobayashi, Julien Gibelin, Dong-Wook Kim, O. Aktas, V. Lapoux, K. Yoshida, M. M. Juhász, Kamila Sieja, Zaihong Yang, I. Murray, K. I. Hahn, T. Kobayashi, X. X. Xu, Si-Ge Chen, P. A. Söderström, Victor Vaquero, Thomas Aumann, and C. Hilaire
Subjects: Physics, 010308 nuclear & particles physics, Island of inversion, 0103 physical sciences, Geophysics, 010306 general physics, 01 natural sciences
Published: 2021
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17. First spectroscopic study of $^{51}$Ar by the (p,2p) reaction

Author: Zs. Dombradi, S. Y. Park, T. Isobe, F. Browne, K. Moschner, Thomas Aumann, R.-B. Gerst, F. Château, Kathrin Wimmer, X. X. Xu, Z. Elekes, L. Zanetti, Hideaki Otsu, B. D. Linh, Hirofumi Yamada, Si-Ge Chen, P. A. Söderström, Yutaka Utsuno, Igor Gašparić, H. N. Liu, Jenny Lee, Zaihong Yang, I. Murray, Yasuhiro Togano, F. Flavigny, K. I. Hahn, L. Stuhl, Yuya Kubota, V. Wagner, Tomohiro Uesaka, A. Giganon, D. Kim, M. MacCormick, C. Lehr, V. Panin, L. X. Chung, P. Koseoglou, T. Lokotko, Y.L. Sun, E. Sahin, K. Yoneda, Victor Vaquero, M. L. Cortés, Takashi Nakamura, S. Franchoo, P. Doornenbal, Satoshi Takeuchi, Masahiro Yasuda, O. Aktas, A. Gillibert, V. Lapoux, Nobuyuki Chiga, Takaharu Otsuka, T. Koiwai, Hiroyoshi Sakurai, T. Motobayashi, M. M. Juhász, Kazuki Yoshida, David Steppenbeck, Julien Gibelin, H. Törnqvist, Toshio Kobayashi, Kazuyuki Ogata, W. Rodriguez, N. L. Achouri, C. Hilaire, S. Wang, Donghang Yan, N. Paul, A. Obertelli, J. M. Gheller, Yosuke Kondo, V. Werner, D. Calvet, D. M. Rossi, Masaki Sasano, H. Baba, D. Sohler, A. Corsi, A. Delbart, 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 de Physique Nucléaire d'Orsay (IPNO), 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), 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)-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)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), RIKEN Nishina Center for Accelerator-Based Science, European Research Council, European Commission, Helmholtz International Center for FAIR, German Research Foundation, Alexander von Humboldt Foundation, Ministry of Science and Technology of Vietnam, Government of South Korea, Agencia Estatal de Investigación (España), Federal Ministry of Education and Research (Germany), Helmholtz Graduate School for Hadron and Ion Research, and National Research, Development and Innovation Office (Hungary)
Subjects: Nuclear and High Energy Physics, Shell closure, γ -ray spectroscopy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 0103 physical sciences, Bound state, nuclear shell model, proton knock-out reaction, gamma-ray spectroscopy, invariant-mass method, radioactive beams, Invariant mass, Neutron, ddc:530, Nuclear structure, 010306 general physics, Spectroscopy, Physics, Valence (chemistry), Proton knock-out reaction, 010308 nuclear & particles physics, Invariant mass method, Isotopes of argon, lcsh:QC1-999, Excited state, γ-ray spectroscopy, Atomic physics, lcsh:Physics
Abstract: 8 pags., 4 figs., 3 tabs., The nuclear structure of 51Ar, an uncharted territory so far, was studied by the (p,2p) reaction using γ-ray spectroscopy for the bound states and the invariant mass method for the unbound states. Two peaks were detected in the γ-ray spectrum and six peaks were observed in the 50Ar+n relative energy spectrum. Comparing the results to our shell-model calculations, two bound and six unbound states were established. Three of the unbound states could only be placed tentatively due to the low number of counts in the relative energy spectrum of events associated with the decay through the first excited state of 50Ar. The low cross sections populating the two bound states of 51Ar could be interpreted as a clear signature for the presence of significant subshell closures at neutron numbers 32 and 34 in argon isotopes. It was also revealed that due to the two valence holes, unbound collective states coexist with individual-particle states in 51Ar., We are very grateful to the RIKEN Nishina Center accelerator staff for providing the stable beam and to the BigRIPS team for the smooth operation of the secondary beams. The development of the MINOS device has been supported by the European Research Council through the ERC Grant No. MINOS-258567. F. B. was supported by the RIKEN Special Postdoctoral Researcher Program. K. O. acknowledges the support by Grant-in-Aid for Scientific Research JP16K05352. Y. U. acknowledges the support by Grant-in-Aid for Scientific Research 20K03981. Y. L. S. acknowledges the support of Marie Skłodowska-Curie Individual Fellowship (H2020-MSCA-IF-2015-705023) from the European Union and the support from the Helmholtz International Center for FAIR. H. N. L. acknowledges the support from the Enhanced Eurotalents program (PCOFUND-GA-2013-600382) co-funded by CEA and the European Union. T. A., C. L., D. R., H. T., V. W., L. Z., H. N. L., V. W. and A. O. acknowledge the support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Project No. 279384907-SFB 1245. R. B. G. acknowledges the support from the DFG under Grant No. BL 1513/1-1. Y. L. S. and A. O. acknowledge the support from the Alexander von Humboldt Foundation. B. D. L. and L. X. C. acknowledge the support from the Vietnam Ministry of Science and Technology under Grant No. ĐTCB.01/21/VKHKTHN. I. G. has been supported by HIC for FAIR and HRZZ under project No. 1257 and 7194. K. I. H., D. K. and S. Y. P. acknowledge the support from the NRF grant funded by the Korea government (No. 2017R1A2B2012382 and 2019M7A1A1033186). F. B. acknowledge the support from the RIKEN Special Postdoctoral Researcher Program. D. S. and Z. E. were supported by projects No. GINOP-2.3.3-15-2016-00034 and No. K128947. V. V. acknowledges support from the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P. V. W. and P. K. acknowledge the support from BMBF grants 05P15RDFN1 and 05P19RDFN1. P. K. acknowledges support from HGS-HIRe. This work was also supported by NKFIH (114454).
Published: 2021
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18. N=32 shell closure below calcium: Low-lying structure of Ar50

Author: Nobuyuki Chiga, K. Moschner, T. Koiwai, Hiroyoshi Sakurai, V. Lapoux, A. Gillibert, Yutaka Utsuno, D. Calvet, T. Isobe, Kathrin Wimmer, T. Motobayashi, Jenny Lee, Achim Schwenk, H. Toernqvist, Yuya Kubota, Victor Vaquero, R.-B. Gerst, F. Château, W. Rodriguez, N. Shimizu, B. D. Linh, D. M. Rossi, Masahiro Yasuda, Tomohiro Uesaka, Hideaki Otsu, Igor Gašparić, H. N. Liu, V. Panin, H. Baba, Kazuyuki Ogata, L. X. Chung, S. Y. Park, Julien Gibelin, Hirofumi Yamada, K. Yoshida, C. Lehr, Duo Yan, L. Achouri, Zaihong Yang, L. Stuhl, A. Giganon, I. Murray, S. Wang, N. Paul, L. Zanetti, E. Sahin, Y. L. Sun, J. Simonis, A. Obertelli, K. Yoneda, C. Hilaire, K. I. Hahn, V. Werner, David Steppenbeck, Jason D. Holt, P. Doornenbal, A. Delbart, M. MacCormick, P. Koseoglou, J. M. Gheller, Alessandra Corsi, Thomas Aumann, Masaki Sasano, Dóra Sohler, Satoshi Takeuchi, M. L. Cortés, S. Franchoo, T. Kobayashi, F. Flavigny, X. X. Xu, Si-Ge Chen, P. A. Söderström, Dong-Wook Kim, F. Browne, O. Aktas, Yosuke Kondo, Yasuhiro Togano, T. Lokotko, Takashi Nakamura, Javier Fernandez Menendez, and V. Wagner
Subjects: Physics, 010308 nuclear & particles physics, 0103 physical sciences, Closure (topology), Shell (structure), Calcium low, 010306 general physics, 01 natural sciences, Molecular physics
Published: 2020
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19. Shell structure of the neutron-rich isotopes Co69,71,73

Author: M. Lettmann, A. Gillibert, Alessandra Corsi, David Steppenbeck, S. Leblond, Yoshiaki Shiga, K. Yoshida, Toshiyuki Sumikama, Ryo Taniuchi, A. Gottardo, F. Nowacki, Jenny Lee, V. Lapoux, Yuya Kubota, C. Péron, A. Delbart, Shunji Nishimura, G. Authelet, Si-Ge Chen, P. A. Söderström, C. Louchart, J. M. Gheller, T. Miyazaki, Alan Peyaud, C. M. Shand, Satoshi Takeuchi, Masafumi Matsushita, F. Giacoppo, H. Baba, Satoru Momiyama, S. Franchoo, E. Sahin, Zhenci Xu, Jinguang Wu, Shuichi Ota, V. Werner, Hideaki Otsu, Alfredo Poves, L. X. Chung, Megumi Niikura, C. Santamaria, Tomohiro Uesaka, I. Stefan, K. Matsui, P. Doornenbal, Kazuyuki Ogata, F. Browne, Masaki Sasano, Zs. Dombrádi, Shoko Koyama, Z. Korkulu, Zs. Vajta, K. Hadynska-Klek, T. Lokotko, Z. Patel, L. Olivier, H. Wang, R. Lozeva, A. Obertelli, Hiroyoshi Sakurai, T. Motobayashi, E. C. Pollacco, J.-Y. Roussé, D. Calvet, T. Isobe, F. Château, and Daisuke Suzuki
Subjects: Physics, Isotope, 010308 nuclear & particles physics, Nuclear structure, Impulse (physics), 7. Clean energy, 01 natural sciences, Coincidence, Nuclear physics, MINOS, 0103 physical sciences, Neutron, Detector array, Nuclear Experiment, 010306 general physics, Excitation
Abstract: The structures of the neutron-rich Co69,71,73 isotopes were investigated via (p,2p) knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Isotopes of interest were studied using the DALI2 γ-ray detector array combined with the MINOS target and tracker system. Level schemes were reconstructed using the γ-γ coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations using the Lenzi-Nowacki-Poves-Sieja LNPS and PFSDG-U interactions suggests coexistence of spherical and deformed shapes at low excitation energies in the Co69,71,73 isotopes. The distorted-wave impulse approximation (DWIA) framework was used to calculate the single-particle cross sections. These values were compared with the experimental findings.
Published: 2020
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20. Studying the Exotic Decay $^{70}Kr$ $\rightarrow$ $^{70}Br$

Author: Daiki Nishimura, G. de Angelis, Hiroyoshi Sakurai, Y. Shimizu, P. A. Söderström, Shunji Nishimura, S. Yagi, C. Magron, J. Agramunt, V. Guadilla, JJ Liu, H. Oikawa, S. M. Lenzi, Y. Takei, N. Kurz, W. Gelletly, S. Chen, A. I. Morales, F. Recchia, E. Ganioglu, J. Giovinazzo, H. Baba, Y. Fujita, V. H. Phong, Gabor Kiss, F. Diel, T. Goigoux, H. Suzuki, D. S. Ahn, Zs. Dombradi, T. Kurtukian Nieto, Jin Wu, P. Aguilera, J. Eberth, N. Fukuda, Jenny Lee, B. Rubio, F. Molina, T. Isobe, P. J. Davies, I. Kojouharov, P. Ascher, M. Tanaka, Alejandro Algora, Naohito Inabe, B. Blank, Toshiyuki Sumikama, Hiroyuki Takeda, S. E.A. Orrigo, P. Doornebal, A. Montaner-Pizá, D. Lubos, C. Borcea, D. R. Napoli, M. Gerbaux, H. Shaffner, S. Grévy, W. Korten, A. Horvath, Toshiyuki Kubo, A. Boso, Shigeru Kubono, A. Vitez-Sveiczer, T. Lokotko, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-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), 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), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), 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: Nuclear physics, Physics, 010308 nuclear & particles physics, 0103 physical sciences, General Physics and Astronomy, ddc:530, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences
Abstract: Acta physica Polonica / B 51(3), 587 (2020). doi:10.5506/APhysPolB.51.587, Published by Inst. of Physics, Jagellonian Univ., Cracow
Published: 2020
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21. Shell evolution of $N=40$ isotones towards $^{60}$Ca: First spectroscopy of $^{62}$Ti

Author: Masaki Sasano, S. M. Lenzi, Kazuki Yoshida, E. Sahin, V. Wagner, Hiroyoshi Sakurai, F. Nowacki, T. Isobe, W. Rodriguez, P. Doornenbal, Donghang Yan, D. Kim, T. Motobayashi, M.L. Cortés, Jason D. Holt, V. Lapoux, D. M. Rossi, Toshio Kobayashi, F. Flavigny, A. Giganon, B. D. Linh, F. Château, V. Panin, H. Baba, N. Paul, L. X. Chung, D. Calvet, X. X. Xu, David Steppenbeck, V. Werner, Igor Gašparić, H. N. Liu, A. Delbart, Yosuke Kondo, Si-Ge Chen, L. Achouri, Julien Gibelin, Tomohiro Uesaka, J. M. Gheller, A. Corsi, S. R. Stroberg, Alfredo Poves, Achim Schwenk, Satoshi Takeuchi, Thomas Aumann, R.-B. Gerst, C. Lehr, Jenny Lee, Yasuhiro Togano, C. Hilaire, Y.L. Sun, P. Koseoglou, Nobuyuki Chiga, K. Yoneda, F. Browne, Victor Vaquero, Yuya Kubota, T. Lokotko, T. Koiwai, Zaihong Yang, Takashi Nakamura, S. Wang, J. Simonis, I. Murray, Javier Fernandez Menendez, A. Obertelli, Kazuyuki Ogata, A. Gillibert, H. Toernqvist, M. MacCormick, Masahiro Yasuda, Hideaki Otsu, K. I. Hahn, L. Stuhl, O. Aktas, Hirofumi Yamada, Dóra Sohler, S. Franchoo, Tomás R. Rodríguez, L. Zanetti, K. Moschner, Kathrin Wimmer, S. Y. Park, P. A. Söderström, 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 Pluridisciplinaire Hubert Curien (IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), 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)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut de Physique Nucléaire d'Orsay (IPNO), 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), UAM. Departamento de Física Teórica, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), 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), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), RIKEN Nishina Center for Accelerator-Based Science, Japan Society for the Promotion of Science, Ministerio de Ciencia, Innovación y Universidades (España), Ministry of Science and Technology of Vietnam, Helmholtz International Center for FAIR, Croatian Science Foundation, National Research, Development and Innovation Office (Hungary), Ministerio de Economía y Competitividad (España), National Research Foundation of Korea, European Commission, Natural Sciences and Engineering Research Council of Canada, Federal Ministry of Education and Research (Germany), and National Research Council of Canada
Subjects: Nuclear and High Energy Physics, Nuclear Theory, Ab initio, FOS: Physical sciences, Shell evolution, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Radioactive beams, Gamma-ray spectroscopy, Nuclear Theory (nucl-th), 0103 physical sciences, ddc:530, Nuclear Experiment (nucl-ex), 010306 general physics, Spectroscopy, Nuclear Experiment, Physics, 010308 nuclear & particles physics, Island of inversion, Isotone, Starke Wechselwirkung und exotische Kerne – Abteilung Blaum, Física, lcsh:QC1-999, Excited state, Quadrupole, Atomic physics, Nucleon, Ground state, lcsh:Physics
Abstract: 7 pags., 4 figs., 1 tab., Excited states in the N=40 isotone Ti were populated via the V(p,2p)Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using γ-ray spectroscopy. The energies of the 2 →0 and 4 →2 transitions, observed here for the first time, indicate a deformed Ti ground state. These energies are increased compared to the neighboring Cr and Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for Ti show a dominant configuration with four neutrons excited across the N=40 gap. Likewise, they indicate that the N=40 island of inversion extends down to Z=20, disfavoring a possible doubly magic character of the elusive Ca., We thank the RIKEN Nishina Center accelerator staff and the Bi-gRIPS team for the stable operation of the high-intensity Zn beam and for the preparation of the secondary beam setting. K.O. ac-knowledges the support by Grant-in-Aid for Scientific Research of the Japan Society for the Promotion of Science (JSPS) JP16K05352. A.P. is supported in part by the Ministerio de Ciencia, Innovación y Universidades (Spain), Severo Ochoa Programme SEV-2016-0597 and grant PGC-2018-94583. F.B. is supported by the RIKEN Spe-cial Postdoctoral Researcher Program. L.X.C. and B.D.L. would like to thank the Vietnam Ministry of Science and Technology (MOST) for its support through the Physics Development Program Grant No. ÐTÐLCN.25/18. I.G. has been supported by HIC for FAIR and Croatian Science Foundation under projects no. 1257 and 7194. D. So. was supported by the the European Regional Develop-ment Fund contract No. GINOP-2.3.3-15-2016-00034 and the National Research, Development and Innovation Fund of Hungary via Project No. K128947. V.V. acknowledges support from the Span-ish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P. K.I.H., D.K. and S.Y.P. acknowledge the sup-port from the National Research Foundation of Korea grant No. 2018R1A5A1025563 and 2019M7A1A1033186. The development of MINOS was supported by the European Research Council through the ERC Grant No. MINOS-258567. This work was also supported by the JSPS KAKENHI Grant No. 18K03639, MEXT as “Priority is-sue on post-K computer” (Elucidation of the fundamental laws and evolution of the universe), the Joint Institute for Computational Fundamental Science (JICFuS), the CNS-RIKEN joint project for large-scale nuclear structure calculations, Natural Sciences and Engineering Research Council (NSERC) of Canada, the Deutsche Forschungsgemeinschaft – Projektnummer 279384907 – SFB 1245, the PRISMA Cluster of Excellence, and the BMBF under Contracts No. 05P18RDFN1 and 05P19RDFN1. TRIUMF receives funding via a contribution through the National Research Council Canada. Com-putations were performed at the Jülich Supercomputing Center (JURECA)
Published: 2020
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22. Quasifree Neutron Knockout from Ca54 Corroborates Arising N=34 Neutron Magic Number

Author: V. Wagner, V. Somà, F. Flavigny, K. Moschner, S. Y. Park, V. Panin, Kathrin Wimmer, M. MacCormick, S. Takeuchi, M. L. Cortés, S. Franchoo, Hideaki Otsu, D. Calvet, D. M. Rossi, Toshio Kobayashi, K. Yoneda, Tomohiro Uesaka, Masaki Sasano, T. Lokotko, P. Koseoglou, Dóra Sohler, H. Baba, N. Paul, P. A. Söderström, David Steppenbeck, Nobuyuki Chiga, E. Sahin, Petr Navrátil, Thomas Aumann, Takashi Nakamura, F. Browne, S. J. Chen, Donghang Yan, V. Werner, T. Isobe, R.-B. Gerst, P. Doornenbal, T. Koiwai, F. Château, A. Corsi, A. Gillibert, Takaharu Otsuka, Hiroyoshi Sakurai, A. Delbart, F. Raimondi, H. Yamada, Shuopei Wang, Y. L. Sun, Victor Vaquero, T. Motobayashi, L. X. Chung, H. Törnqvist, J. M. Gheller, Yasuhiro Togano, W. Rodriguez, Y. Chazono, A. Giganon, Carlo Barbieri, Kazuyuki Ogata, C. Lehr, Masahiro Yasuda, C. Hilaire, N. L. Achouri, Yosuke Kondo, Julien Gibelin, X. X. Xu, B. D. Linh, J. Kahlbow, Igor Gašparić, H. N. Liu, A. Obertelli, L. Zanetti, Yutaka Utsuno, Jenny Lee, Yuya Kubota, V. Lapoux, K. Yoshida, Dong-Wook Kim, O. Aktas, Zaihong Yang, I. Murray, K. I. Hahn, and L. Stuhl
Subjects: Physics, Hydrogen, Nuclear Theory, General Physics and Astronomy, chemistry.chemical_element, Impulse (physics), 01 natural sciences, Vertex (geometry), Isotopes of calcium, Transverse plane, chemistry, Excited state, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Excitation
Abstract: Exclusive cross sections and momentum distributions have been measured for quasifree one-neutron knockout reactions from a ^{54}Ca beam striking on a liquid hydrogen target at ∼200 MeV/u. A significantly larger cross section to the p_{3/2} state compared to the f_{5/2} state observed in the excitation of ^{53}Ca provides direct evidence for the nature of the N=34 shell closure. This finding corroborates the arising of a new shell closure in neutron-rich calcium isotopes. The distorted-wave impulse approximation reaction formalism with shell model calculations using the effective GXPF1Bs interaction and ab initio calculations concur our experimental findings. Obtained transverse and parallel momentum distributions demonstrate the sensitivity of quasifree one-neutron knockout in inverse kinematics on a thick liquid hydrogen target with the reaction vertex reconstructed to final state spin-parity assignments.
Published: 2019
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23. In-beam γ -ray spectroscopy of Te136 at relativistic energies

Author: Yoshiaki Shiga, Takane Saito, Ryo Taniuchi, E. Sahin, P. Doornenbal, David Steppenbeck, Gry Merete Tveten, R. Orlandi, A. Jungclaus, Jinjia Liu, S. Franchoo, H. Baba, S. Nagamine, F. L. Bello Garrote, Kazuyuki Ogata, Enrique Nácher, K. Hadynska-Klek, M. Yalcinkaya, T. Lokotko, Kathrin Wimmer, Takenori Furumoto, A. Kusoglu, Megumi Niikura, Hiroyoshi Sakurai, T. Motobayashi, Nathan Nakatsuka, Ziye Xu, Toshiaki Ando, Si-Ge Chen, P. A. Söderström, Victor Vaquero, A. M. Moro, Satoru Momiyama, and Zs. Vajta
Subjects: Physics, 010308 nuclear & particles physics, Coulomb excitation, Inelastic scattering, 01 natural sciences, Excited state, 0103 physical sciences, Coulomb, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy, Excitation, Beam (structure)
Abstract: The reduced transition probability B(E2;01+→21+) to the first excited 2+ state of the neutron-rich nucleus Te136, with two protons and two neutrons outside the doubly magic Sn132 core, was measured via Coulomb excitation at relativistic energies at the RIKEN Radioactive Isotope Beam Factory. A value of B(E2)=0.191(26) e2b2 was extracted from the measured inelastic scattering cross section on an Au target taking into account the contributions from both Coulomb and nuclear excitations. In addition, an upper limit for the transition strength to a 2+ state of mixed-symmetry character in the excitation energy range of 1.5-2.2 MeV was determined and compared to the predictions of various theoretical calculations. Because of the high statistics gathered in the present experiment the error of the deduced B(E2) value is dominated by the systematic uncertainties involved in the analysis of Coulomb excitation experiments at beam energies around 150 MeV/u. Therefore, the latter are for the first time assessed in detail in the present work.
Published: 2019
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24. How Robust is the N=34 Subshell Closure? First Spectroscopy of Ar52

Author: Nobuyuki Chiga, T. Lokotko, Si Chen, T. Koiwai, Takashi Nakamura, D. Calvet, K. Moschner, E. Sahin, Yosuke Kondo, A. Corsi, N.L. Achouri, Kathrin Wimmer, T. Kobayashi, F. Browne, X. X. Xu, David Steppenbeck, B. D. Linh, A. Delbart, J. M. Gheller, V. Wagner, H. Törnqvist, P. Doornenbal, M. MacCormick, R.-B. Gerst, Igor Gašparić, C. Lehr, Hiroyoshi Sakurai, Masahiro Yasuda, C. Hilaire, H.N. Liu, A. Giganon, F. Flavigny, M. L. Cortés, T. Motobayashi, S. Franchoo, Thomas Aumann, C.A. Bertulani, A. Gillibert, V. Panin, Hideaki Otsu, L. X. Chung, P. A. Söderström, Gustav R. Jansen, Hirofumi Yamada, Masaki Sasano, R. Stroberg, D. Sohler, Julien Gibelin, L. Zanetti, Victor Vaquero, V. Lapoux, T. Isobe, N. Paul, S. Wang, Yasuhiro Togano, Jenny Lee, Achim Schwenk, Yuya Kubota, Satoshi Takeuchi, V. Werner, A. Obertelli, F. Château, P. Koseoglou, Gaute Hagen, Dong-Wook Kim, O. Aktas, Zaihong Yang, I. Murray, K. I. Hahn, L. Stuhl, Jason D. Holt, Tomohiro Uesaka, K. Yoneda, S. Y. Park, Duo Yan, D. M. Rossi, H. Baba, Y. L. Sun, T. D. Morris, and W. Rodriguez
Subjects: Physics, Isotope, Closure (topology), General Physics and Astronomy, 01 natural sciences, 3. Good health, Neutron number, 0103 physical sciences, Atomic number, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy, Nuclear theory, Excitation, Energy (signal processing)
Abstract: The first γ-ray spectroscopy of ^{52}Ar, with the neutron number N=34, was measured using the ^{53}K(p,2p) one-proton removal reaction at ∼210 MeV/u at the RIBF facility. The 2_{1}^{+} excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N>20. This result is the first experimental signature of the persistence of the N=34 subshell closure beyond ^{54}Ca, i.e., below the magic proton number Z=20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2_{1}^{+} systematics of neutron-rich Ar isotopes, and support a N=34 subshell closure in ^{52}Ar.
Published: 2019
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25. Spectroscopy of neutron-rich scandium isotopes

Author: A. Delbart, T. Motobayashi, L. Zanetti, Julien Gibelin, Tomohiro Uesaka, T. Kobayashi, X. X. Xu, H. Toernqvist, Si-Ge Chen, P. A. Söderström, S. Wang, F. Flavigny, A. Obertelli, V. Wagner, M. Lettmann, D. Calvet, J. M. Gheller, T. Isobe, A. Giganon, F. Château, Thomas Aumann, Makoto Yasuda, Victor Vaquero, A. Gillibert, V. Panin, L. X. Chung, E. Sahin, S. Y. Park, T. Lokotko, Duo Yan, P. Doornenbal, K. Moschner, M. MacCormick, C. Hilaire, Kathrin Wimmer, Alessandra Corsi, Satoshi Takeuchi, Takashi Nakamura, R.-B. Gerst, B. D. Linh, M. L. Cortés, S. Franchoo, Igor Gašparić, H. N. Liu, K. Yoneda, C. Lehr, Jenny Lee, F. Browne, Yuya Kubota, Masaki Sasano, N. Paul, D. M. Rossi, V. Werner, Yasuhiro Togano, Yosuke Kondo, H. Baba, N. L. Achouri, Hideaki Otsu, Hirofumi Yamada, Y. L. Sun, Dong-Wook Kim, O. Aktas, V. Lapoux, Zaihong Yang, I. Murray, K. I. Hahn, David Steppenbeck, L. Stuhl, W. Rodriguez, Nobuyuki Chiga, T. Koiwai, Norbert Pietralla, D. Sohler, P. Koseoglou, Hiroyoshi Sakurai, RIKEN Nishina Center for Accelerator-Based Science, Technische Universität Darmstadt, Helmholtz Centre for Heavy Ion Research, Federal Ministry of Education and Research (Germany), 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 de Physique Nucléaire d'Orsay (IPNO), 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), 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)-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)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, History, Isotope, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, chemistry.chemical_element, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 7. Clean energy, Computer Science Applications, Education, International school, Neutron physics, Nuclear physics, chemistry, 0103 physical sciences, Physics::Accelerator Physics, ddc:530, Neutron, Scandium, Nuclear Experiment, 010306 general physics, Spectroscopy
Abstract: 7 pags., 7 figs. -- XXIII International School on Nuclear Physics, Neutron Physics and Applications 22-28 September 2019, Varna, Bulgaria, Within the SEASTAR III campaign at the Radioactive Isotope Beam Factory, at the RIKEN Nishina Center, neutron-rich isotopes in the vicinity of 53K were produced from the fragmentation of the primary 70Zn beam on a 9Be target. After nucleon knockout reactions on the secondary liquid hydrogen MINOS target the known γ rays of the neutron-rich 55Sc isotope were observed (shown in this proceedings) and γ rays from 57,59Sc isotopes have been identified for the first time. The evolution of the occupied nucleon orbitals of these nuclei in the ground and excited state is investigated under the prism of the tensor force., We are grateful to the RIKEN Nishina Center accelerator staff for their work in the primary beam delivery and the BigRIPS team for preparing the secondary beams. This work was supported by the cooperation between TU Darmstadt and the GSI Helmholtz Center for Heavy Ion Research, by the Helmholtz Graduate School for Hadron and Ion Research for FAIR and its abroad program and the BMBF under grant No. 05P19RDFN1. D.S. was supported by projects No. GINOP2.3.3-15-2016-00034 and No. K128947.
Published: 2020
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26. Restoration of the natural E(1/21+) - E(3/21+) energy splitting in odd-K isotopes towards N = 40

Author: David Steppenbeck, B. D. Linh, H. Törnqvist, Igor Gašparić, H. N. Liu, Kazuki Yoshida, Yosuke Kondo, Toshio Kobayashi, P. A. Söderström, K. Yoneda, N. Paul, Carlo Barbieri, S. Y. Park, D. M. Rossi, V. Lapoux, Donghang Yan, H. Baba, K. Moschner, Masaki Sasano, V. Werner, Yutaka Utsuno, Yoshiki Chazono, S. Wang, D. Sohler, Zaihong Yang, I. Murray, K. I. Hahn, L. Stuhl, Kathrin Wimmer, Jenny Lee, J. M. Gheller, Victor Vaquero, R.-B. Gerst, Takaharu Otsuka, F. Browne, A. Obertelli, Nobuyuki Chiga, D. Calvet, T. Isobe, Hiroyoshi Sakurai, T. Koiwai, Yuya Kubota, C. Hilaire, T. Motobayashi, F. Nowacki, F. Château, A. Delbart, C. Lehr, A. Gillibert, M. MacCormick, Julien Gibelin, A. Corsi, X. X. Xu, V. Panin, M. L. Cortés, Thomas Aumann, O. Aktas, S. Franchoo, Si-Ge Chen, L. X. Chung, L. Zanetti, A. Giganon, Francesco Raimondi, Hideaki Otsu, Hirofumi Yamada, Tomohiro Uesaka, W. Rodriguez, F. Flavigny, Yasuhiro Togano, T. Lokotko, E. Sahin, N.L. Achouri, Y.L. Sun, Takashi Nakamura, Petr Navrátil, P. Doornenbal, Thomas Duguet, V. Wagner, Satoshi Takeuchi, D. Kim, V. Somà, Masahiro Yasuda, Kazuyuki Ogata, and P. Koseoglou
Subjects: Physics, Nuclear and High Energy Physics, Chemical substance, Isotope, 010308 nuclear & particles physics, SHELL model, 01 natural sciences, Vertex (geometry), Ab initio quantum chemistry methods, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics, Nucleon, Spectroscopy
Abstract: We report on the first γ-ray spectroscopy of 51,53K produced via the 52,54Ca(p,2p) reactions at ∼250 MeV/nucleon. Unambiguous final-state angular-momentum assignments were achieved for beam intensities down to few particles per second by using a new technique based on reaction vertex tracking combined with a thick liquid-hydrogen target. Through γ-ray spectroscopy and exclusive parallel momentum distribution analysis, 3/2+ ground states and 1/2+ first excited states in 51,53K were established quantifying the natural ordering of the 1 d 3 / 2 and 2 s 1 / 2 proton-hole states that are restored at N = 32 and 34. State-of-the-art ab initio calculations and shell-model calculations with improved phenomenological effective interactions reproduce the present data and predict consistently the increase of the E(1/2 1 + ) - E(3/2 1 + ) energy differences towards N = 40.
Published: 2020
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27. Proton elastic scattering at 200 A MeV and high momentum transfers of 1.7–2.7 fm−1 as a probe of the nuclear matter density of 6He

Author: Yohei Shimizu, Zh Yang, Masaki Sasano, K. Yoneda, Y. Ando, T. Akieda, S. Nakai, Masanori Dozono, T. Tomai, A. Galindo-Uribarri, I. Stefan, Atsumi Saito, H. Sato, M. Yasuda, Kaori Kaki, Kenjiro Miki, A. Ni, Yuya Kubota, Yosuke Kondo, S. Leblond, Didier Beaumel, Kimiko Sekiguchi, N. Chiga, Juzo Zenihiro, A. Watanabe, Tetsuo Noro, Takashi Kobayashi, Satoshi Sakaguchi, L. Stuhl, Shoichiro Kawase, Yohei Matsuda, S. Park, Satoru Terashima, Shuichi Ota, W. Kim, T. Lokotko, V. Panin, T. Mukai, T. Wakui, B. Heffron, Kenichiro Tateishi, Tomotsugu Wakasa, Motonobu Takaki, T. Ozaki, H. Sakai, Yukie Maeda, Tomohiro Uesaka, H. Kon, Yoshiki Wada, Hideaki Otsu, T. Motobayashi, J. Yasuda, E. Milman, S. Chebotaryov, K. Taniue, A. Hirayama, H. Lee, Takashi Nakamura, Tadaaki Isobe, H. Yamada, Yasuhiro Togano, M. Assie, 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), 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: Elastic scattering, Physics, Inverse kinematics, 010308 nuclear & particles physics, D27 Reactions induced by unstable nuclei, General Physics and Astronomy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Impulse (physics), Nuclear matter, 7. Clean energy, 01 natural sciences, Computational physics, medicine.anatomical_structure, 0103 physical sciences, medicine, D11 Models of nuclear structure, Neutron, Halo, Nuclear Experiment, 010306 general physics, Nucleus, Order of magnitude
Abstract: International audience; Differential cross sections of p–6He elastic scattering were measured in inverse kinematics at an incident energy of 200 A MeV, covering the high momentum transfer region of 1.7–2.7 fm−1. The sensitivity of the elastic scattering at low and high momentum transfers to the density distribution was investigated quantitatively using relativistic impulse approximation calculations. In the high momentum transfer region, where the present data were taken, the differential cross section has an order of magnitude higher sensitivity to the inner part of the 6He density relative to the peripheral part (15:1). This feature makes the obtained data valuable for the deduction of the inner part of the 6He density. The data were compared to a set of calculations assuming different proton and neutron density profiles of 6He. The data are well reproduced by the calculation assuming almost the same profiles of proton and neutron densities around the center of 6He, and a proton profile reproducing the known point-proton radius of 1.94 fm. This finding is consistent with the assumption that the 6He nucleus consists of a rigid α-like core with a two-neutron halo.
Published: 2018
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28. Simultaneous investigation of the T=1(Jπ=0+) and T=0(Jπ=9+) β decays in Br70

Author: A. I. Morales, A. Algora, B. Rubio, K. Kaneko, S. Nishimura, P. Aguilera, S. E. A. Orrigo, F. Molina, G. de Angelis, F. Recchia, G. Kiss, V. H. Phong, J. Wu, D. Nishimura, H. Oikawa, T. Goigoux, J. Giovinazzo, P. Ascher, J. Agramunt, D. S. Ahn, H. Baba, B. Blank, C. Borcea, A. Boso, P. Davies, F. Diel, Zs. Dombrádi, P. Doornenbal, J. Eberth, G. de France, Y. Fujita, N. Fukuda, E. Ganioglu, W. Gelletly, M. Gerbaux, S. Grévy, V. Guadilla, N. Inabe, T. Isobe, I. Kojouharov, W. Korten, T. Kubo, S. Kubono, T. Kurtukián Nieto, N. Kurz, J. Lee, S. Lenzi, J. Liu, T. Lokotko, D. Lubos, C. Magron, A. Montaner-Pizá, D. R. Napoli, H. Sakurai, H. Schaffner, Y. Shimizu, C. Sidong, P.-A. Söderström, T. Sumikama, H. Suzuki, H. Takeda, Y. Takei, M. Tanaka, and S. Yagi
Subjects: Physics, Spins, 010308 nuclear & particles physics, Branching fraction, Time decay, Prolate spheroid, 01 natural sciences, Nuclear physics, Excited state, 0103 physical sciences, Pi, Atomic physics, 010306 general physics, Ground state, Excitation
Abstract: The $\beta$ decay of the odd-odd nucleus $^{70}$Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The $T=0$ ($J^{\pi}=9^+$) and $T=1$ ($J^{\pi}=0^+$) isomers have both been produced in in-flight fragmentation of $^{78}$Kr with ratios of 41.6(8)\% and 58.4(8)\%, respectively. A half-life of $t_{1/2}=2157^{+53}_{-49}$ ms has been measured for the $J^{\pi}=9^+$ isomer from $\gamma$-ray time decay analysis. Based on this result, we provide a new value of the half-life for the $J^{\pi}=0^+$ ground state of $^{70}$Br, $t_{1/2}=78.42\pm0.51$ ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the $2^+_1$ state in the daughter nucleus $^{70}$Se, $R(2^+_1)=1.3\pm1.1\%$. We also report four new low-intensity $\gamma$-ray transitions at 661, 1103, 1561, and 1749 keV following the $\beta$ decay of the $J^{\pi}=9^+$ isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in $^{70}$Se with most probable spins and parities of $J^{\pi}=(6^+)$ and $(8^+)$, respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.
Published: 2017
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29. Gamma Decay of Unbound Neutron-Hole States in Sn133

Author: Megumi Niikura, Ryo Taniuchi, A. Kusoglu, Tomoki Saito, Kathrin Wimmer, JJ Liu, T. Lokotko, Gry Merete Tveten, S. Franchoo, S. Nagamine, Victor Vaquero, R. Orlandi, E. Sahin, Zhenci Xu, A. Jungclaus, P. Doornenbal, Toshiaki Ando, Si-Ge Chen, P. A. Söderström, A. Gargano, K. Hadynska-Klek, Enrique Nácher, David Steppenbeck, Noritsugu Nakatsuka, J. A. Tostevin, Zs. Vajta, Yoshiaki Shiga, M. Yalcinkaya, Satoru Momiyama, Hiroyoshi Sakurai, T. Motobayashi, F. L. Bello Garrote, and H. Baba
Subjects: Physics, Range (particle radiation), Decay scheme, 010308 nuclear & particles physics, Neutron emission, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Gamma ray, Nuclear structure, General Physics and Astronomy, 01 natural sciences, Nuclear physics, 13. Climate action, Excited state, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, s-process
Abstract: Excited states in the nucleus 133Sn, with one neutron outside the doubly-magic 132Sn core, were populated following one-neutron knockout from a 134Sn beam on a carbon target at relativistic energies at the Radioactive Isotope Beam Factory at RIKEN. Besides the rays emitted in the decay of the known neutron single-particle states in 133Sn additional strength in the energy range 3.5-5.5 MeV was observed for the fi rst time. Since the neutron-separation energy of 133Sn is low, Sn=2.402(4) MeV, this observation provides direct evidence for the radiative decay of neutron- unbound states in this nucleus. The ability of electromagnetic decay to compete successfully with neutron emission at energies as high as 3 MeV above threshold is attributed to a mismatch between the wave functions of the initial and final states in the latter case. These fi ndings suggest that in the region south-east of 132Sn nuclear structure effects may play a signifi cant role in the neutron vs. competition in the decay of unbound states. As a consequence, the common neglect of such effects in the evaluation of the neutron-emission probabilities in calculations of global b -decay properties for astrophysical simulations may have to be reconsidered.
Published: 2017
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30. Gamma Decay of Unbound Neutron-Hole States in $^{133}$Sn

Author: V, Vaquero, A, Jungclaus, P, Doornenbal, K, Wimmer, A, Gargano, J A, Tostevin, S, Chen, E, Nácher, E, Sahin, Y, Shiga, D, Steppenbeck, R, Taniuchi, Z Y, Xu, T, Ando, H, Baba, F L Bello, Garrote, S, Franchoo, K, Hadynska-Klek, A, Kusoglu, J, Liu, T, Lokotko, S, Momiyama, T, Motobayashi, S, Nagamine, N, Nakatsuka, M, Niikura, R, Orlandi, T, Saito, H, Sakurai, P A, Söderström, G M, Tveten, Zs, Vajta, M, Yalcinkaya, Institut de Physique Nucléaire d'Orsay (IPNO), 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), and 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)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract: International audience; Excited states in the nucleus Sn133, with one neutron outside the double magic Sn132 core, were populated following one-neutron knockout from a Sn134 beam on a carbon target at relativistic energies at the Radioactive Isotope Beam Factory at RIKEN. Besides the γ rays emitted in the decay of the known neutron single-particle states in Sn133 additional γ strength in the energy range 3.5–5.5 MeV was observed for the first time. Since the neutron-separation energy of Sn133 is low, Sn=2.402(4) MeV, this observation provides direct evidence for the radiative decay of neutron-unbound states in this nucleus. The ability of electromagnetic decay to compete successfully with neutron emission at energies as high as 3 MeV above threshold is attributed to a mismatch between the wave functions of the initial and final states in the latter case. These findings suggest that in the region southeast of Sn132 nuclear structure effects may play a significant role in the neutron versus γ competition in the decay of unbound states. As a consequence, the common neglect of such effects in the evaluation of the neutron-emission probabilities in calculations of global β-decay properties for astrophysical simulations may have to be reconsidered.
Published: 2017
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31. 94 β-Decay Half-Lives of Neutron-Rich _{55}Cs to _{67}Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation

Author: J, Wu, S, Nishimura, G, Lorusso, P, Möller, E, Ideguchi, P-H, Regan, G S, Simpson, P-A, Söderström, P M, Walker, H, Watanabe, Z Y, Xu, H, Baba, F, Browne, R, Daido, P, Doornenbal, Y F, Fang, G, Gey, T, Isobe, P S, Lee, J J, Liu, Z, Li, Z, Korkulu, Z, Patel, V, Phong, S, Rice, H, Sakurai, L, Sinclair, T, Sumikama, M, Tanaka, A, Yagi, Y L, Ye, R, Yokoyama, G X, Zhang, T, Alharbi, N, Aoi, F L, Bello Garrote, G, Benzoni, A M, Bruce, R J, Carroll, K Y, Chae, Z, Dombradi, A, Estrade, A, Gottardo, C J, Griffin, H, Kanaoka, I, Kojouharov, F G, Kondev, S, Kubono, N, Kurz, I, Kuti, S, Lalkovski, G J, Lane, E J, Lee, T, Lokotko, G, Lotay, C-B, Moon, H, Nishibata, I, Nishizuka, C R, Nita, A, Odahara, Zs, Podolyák, O J, Roberts, H, Schaffner, C, Shand, J, Taprogge, S, Terashima, Z, Vajta, and S, Yoshida
Abstract: The β-decay half-lives of 94 neutron-rich nuclei ^{144-151}Cs, ^{146-154}Ba, ^{148-156}La, ^{150-158}Ce, ^{153-160}Pr, ^{156-162}Nd, ^{159-163}Pm, ^{160-166}Sm, ^{161-168}Eu, ^{165-170}Gd, ^{166-172}Tb, ^{169-173}Dy, ^{172-175}Ho, and two isomeric states ^{174m}Er, ^{172m}Dy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for _{58}Ce, _{59}Pr, _{60}Nd, and _{62}Sm, and N=105 for _{63}Eu, _{64}Gd, _{65}Tb, and _{66}Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.
Published: 2016

32. Validation of the ^{10}Be Ground-State Molecular Structure Using ^{10}Be(p,pα)^{6}He Triple Differential Reaction Cross-Section Measurements.

Author: Li PJ, Beaumel D, Lee J, Assié M, Chen S, Franchoo S, Gibelin J, Hammache F, Harada T, Kanada-En'yo Y, Kubota Y, Leblond S, Liang PF, Lokotko T, Lyu M, Marqués FM, Matsuda Y, Ogata K, Otsu H, Rindel E, Stuhl L, Suzuki D, Togano Y, Tomai T, Xu XX, Yoshida K, Zenihiro J, Achouri NL, Aumann T, Baba H, Cardella G, Ceruti S, Stefanescu AI, Corsi A, Frotscher A, Gao J, Gillibert A, Inaba K, Isobe T, Kawabata T, Kitamura N, Kobayashi T, Kondo Y, Kurihara A, Liu HN, Miki H, Nakamura T, Obertelli A, Orr NA, Panin V, Sasano M, Shimada T, Sun YL, Tanaka J, Trache L, Tudor D, Uesaka T, Wang H, Yamada H, Yang ZH, and Yasuda M
Abstract: The cluster structure of the neutron-rich isotope ^{10}Be has been probed via the (p,pα) reaction at 150 MeV/nucleon in inverse kinematics and in quasifree conditions. The populated states of ^{6}He residues were investigated through missing mass spectroscopy. The triple differential cross section for the ground-state transition was extracted for quasifree angle pairs (θ_{p},θ_{α}) and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using successively the Tohsaki-Horiuchi-Schuck-Röpke product wave function and the wave function deduced from antisymmetrized molecular dynamics calculations. The remarkable agreement between calculated and measured cross sections in both shape and magnitude validates the molecular structure description of the ^{10}Be ground-state, configured as an α-α core with two valence neutrons occupying π-type molecular orbitals.
Published: 2023
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33. Multiple Mechanisms in Proton-Induced Nucleon Removal at ∼100 MeV/Nucleon.

Author: Pohl T, Sun YL, Obertelli A, Lee J, Gómez-Ramos M, Ogata K, Yoshida K, Cai BS, Yuan CX, Brown BA, Baba H, Beaumel D, Corsi A, Gao J, Gibelin J, Gillibert A, Hahn KI, Isobe T, Kim D, Kondo Y, Kobayashi T, Kubota Y, Li P, Liang P, Liu HN, Liu J, Lokotko T, Marqués FM, Matsuda Y, Motobayashi T, Nakamura T, Orr NA, Otsu H, Panin V, Park SY, Sakaguchi S, Sasano M, Sato H, Sakurai H, Shimizu Y, Stefanescu AI, Stuhl L, Suzuki D, Togano Y, Tudor D, Uesaka T, Wang H, Xu X, Yang ZH, Yoneda K, and Zenihiro J
Abstract: We report on the first proton-induced single proton- and neutron-removal reactions from the neutron-deficient ^{14}O nucleus with large Fermi-surface asymmetry S_{n}-S_{p}=18.6 MeV at ∼100 MeV/nucleon, a widely used energy regime for rare-isotope studies. The measured inclusive cross sections and parallel momentum distributions of the ^{13}N and ^{13}O residues are compared to the state-of-the-art reaction models, with nuclear structure inputs from many-body shell-model calculations. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively. These multiple reaction mechanisms should be considered in analyses of inclusive one-nucleon removal cross sections measured at intermediate energies for quantitative investigation of single-particle strengths and correlations in atomic nuclei.
Published: 2023
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34. Extended p_{3/2} Neutron Orbital and the N=32 Shell Closure in ^{52}Ca.

Author: Enciu M, Liu HN, Obertelli A, Doornenbal P, Nowacki F, Ogata K, Poves A, Yoshida K, Achouri NL, Baba H, Browne F, Calvet D, Château F, Chen S, Chiga N, Corsi A, Cortés ML, Delbart A, Gheller JM, Giganon A, Gillibert A, Hilaire C, Isobe T, Kobayashi T, Kubota Y, Lapoux V, Motobayashi T, Murray I, Otsu H, Panin V, Paul N, Rodriguez W, Sakurai H, Sasano M, Steppenbeck D, Stuhl L, Sun YL, Togano Y, Uesaka T, Wimmer K, Yoneda K, Aktas O, Aumann T, Chung LX, Flavigny F, Franchoo S, Gasparic I, Gerst RB, Gibelin J, Hahn KI, Kim D, Kondo Y, Koseoglou P, Lee J, Lehr C, Li PJ, Linh BD, Lokotko T, MacCormick M, Moschner K, Nakamura T, Park SY, Rossi D, Sahin E, Söderström PA, Sohler D, Takeuchi S, Toernqvist H, Vaquero V, Wagner V, Wang S, Werner V, Xu X, Yamada H, Yan D, Yang Z, Yasuda M, and Zanetti L
Abstract: The one-neutron knockout from ^{52}Ca in inverse kinematics onto a proton target was performed at ∼230 MeV/nucleon combined with prompt γ spectroscopy. Exclusive quasifree scattering cross sections to bound states in ^{51}Ca and the momentum distributions corresponding to the removal of 1f_{7/2} and 2p_{3/2} neutrons were measured. The cross sections, interpreted within the distorted-wave impulse approximation reaction framework, are consistent with a shell closure at the neutron number N=32, found as strong as at N=28 and N=34 in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 1f_{7/2} and 2p_{3/2} orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the 2p_{3/2} orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.
Published: 2022
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35. Pairing Forces Govern Population of Doubly Magic ^{54}Ca from Direct Reactions.

Author: Browne F, Chen S, Doornenbal P, Obertelli A, Ogata K, Utsuno Y, Yoshida K, Achouri NL, Baba H, Calvet D, Château F, Chiga N, Corsi A, Cortés ML, Delbart A, Gheller JM, Giganon A, Gillibert A, Hilaire C, Isobe T, Kobayashi T, Kubota Y, Lapoux V, Liu HN, Motobayashi T, Murray I, Otsu H, Panin V, Paul N, Rodriguez W, Sakurai H, Sasano M, Steppenbeck D, Stuhl L, Sun YL, Togano Y, Uesaka T, Wimmer K, Yoneda K, Aktas O, Aumann T, Boretzky K, Caesar C, Chung LX, Flavigny F, Franchoo S, Gasparic I, Gerst RB, Gibelin J, Hahn KI, Holl M, Kahlbow J, Kim D, Körper D, Koiwai T, Kondo Y, Koseoglou P, Lee J, Lehr C, Linh BD, Lokotko T, MacCormick M, Miki K, Moschner K, Nakamura T, Park SY, Rossi D, Sahin E, Schindler F, Simon H, Söderström PA, Sohler D, Takeuchi S, Törnqvist H, Tscheuschner J, Vaquero V, Wagner V, Wang S, Werner V, Xu X, Yamada H, Yan D, Yang Z, Yasuda M, and Zanetti L
Abstract: Direct proton-knockout reactions of ^{55}Sc at ∼220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of ^{54}Ca were investigated through γ-ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological internucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the ^{55}Sc ground state with states in ^{54}Ca. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of ^{55}Sc, valence proton removals populated predominantly the ground state of ^{54}Ca. This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
Published: 2021
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36. Quasifree Neutron Knockout from ^{54}Ca Corroborates Arising N=34 Neutron Magic Number.

Author: Chen S, Lee J, Doornenbal P, Obertelli A, Barbieri C, Chazono Y, Navrátil P, Ogata K, Otsuka T, Raimondi F, Somà V, Utsuno Y, Yoshida K, Baba H, Browne F, Calvet D, Château F, Chiga N, Corsi A, Cortés ML, Delbart A, Gheller JM, Giganon A, Gillibert A, Hilaire C, Isobe T, Kahlbow J, Kobayashi T, Kubota Y, Lapoux V, Liu HN, Motobayashi T, Murray I, Otsu H, Panin V, Paul N, Rodriguez W, Sakurai H, Sasano M, Steppenbeck D, Stuhl L, Sun YL, Togano Y, Uesaka T, Wimmer K, Yoneda K, Achouri N, Aktas O, Aumann T, Chung LX, Flavigny F, Franchoo S, Gašparić I, Gerst RB, Gibelin J, Hahn KI, Kim D, Koiwai T, Kondo Y, Koseoglou P, Lehr C, Linh BD, Lokotko T, MacCormick M, Moschner K, Nakamura T, Park SY, Rossi D, Sahin E, Sohler D, Söderström PA, Takeuchi S, Törnqvist H, Vaquero V, Wagner V, Wang S, Werner V, Xu X, Yamada H, Yan D, Yang Z, Yasuda M, and Zanetti L
Abstract: Exclusive cross sections and momentum distributions have been measured for quasifree one-neutron knockout reactions from a ^{54}Ca beam striking on a liquid hydrogen target at ∼200 MeV/u. A significantly larger cross section to the p_{3/2} state compared to the f_{5/2} state observed in the excitation of ^{53}Ca provides direct evidence for the nature of the N=34 shell closure. This finding corroborates the arising of a new shell closure in neutron-rich calcium isotopes. The distorted-wave impulse approximation reaction formalism with shell model calculations using the effective GXPF1Bs interaction and ab initio calculations concur our experimental findings. Obtained transverse and parallel momentum distributions demonstrate the sensitivity of quasifree one-neutron knockout in inverse kinematics on a thick liquid hydrogen target with the reaction vertex reconstructed to final state spin-parity assignments.
Published: 2019
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37. How Robust is the N=34 Subshell Closure? First Spectroscopy of ^{52}Ar.

Author: Liu HN, Obertelli A, Doornenbal P, Bertulani CA, Hagen G, Holt JD, Jansen GR, Morris TD, Schwenk A, Stroberg R, Achouri N, Baba H, Browne F, Calvet D, Château F, Chen S, Chiga N, Corsi A, Cortés ML, Delbart A, Gheller JM, Giganon A, Gillibert A, Hilaire C, Isobe T, Kobayashi T, Kubota Y, Lapoux V, Motobayashi T, Murray I, Otsu H, Panin V, Paul N, Rodriguez W, Sakurai H, Sasano M, Steppenbeck D, Stuhl L, Sun YL, Togano Y, Uesaka T, Wimmer K, Yoneda K, Aktas O, Aumann T, Chung LX, Flavigny F, Franchoo S, Gašparić I, Gerst RB, Gibelin J, Hahn KI, Kim D, Koiwai T, Kondo Y, Koseoglou P, Lee J, Lehr C, Linh BD, Lokotko T, MacCormick M, Moschner K, Nakamura T, Park SY, Rossi D, Sahin E, Sohler D, Söderström PA, Takeuchi S, Törnqvist H, Vaquero V, Wagner V, Wang S, Werner V, Xu X, Yamada H, Yan D, Yang Z, Yasuda M, and Zanetti L
Abstract: The first γ-ray spectroscopy of ^{52}Ar, with the neutron number N=34, was measured using the ^{53}K(p,2p) one-proton removal reaction at ∼210 MeV/u at the RIBF facility. The 2_{1}^{+} excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N>20. This result is the first experimental signature of the persistence of the N=34 subshell closure beyond ^{54}Ca, i.e., below the magic proton number Z=20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2_{1}^{+} systematics of neutron-rich Ar isotopes, and support a N=34 subshell closure in ^{52}Ar.
Published: 2019
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38. Gamma Decay of Unbound Neutron-Hole States in ^{133}Sn.

Author: Vaquero V, Jungclaus A, Doornenbal P, Wimmer K, Gargano A, Tostevin JA, Chen S, Nácher E, Sahin E, Shiga Y, Steppenbeck D, Taniuchi R, Xu ZY, Ando T, Baba H, Garrote FLB, Franchoo S, Hadynska-Klek K, Kusoglu A, Liu J, Lokotko T, Momiyama S, Motobayashi T, Nagamine S, Nakatsuka N, Niikura M, Orlandi R, Saito T, Sakurai H, Söderström PA, Tveten GM, Vajta Z, and Yalcinkaya M
Abstract: Excited states in the nucleus ^{133}Sn, with one neutron outside the double magic ^{132}Sn core, were populated following one-neutron knockout from a ^{134}Sn beam on a carbon target at relativistic energies at the Radioactive Isotope Beam Factory at RIKEN. Besides the γ rays emitted in the decay of the known neutron single-particle states in ^{133}Sn additional γ strength in the energy range 3.5-5.5 MeV was observed for the first time. Since the neutron-separation energy of ^{133}Sn is low, S_{n}=2.402(4) MeV, this observation provides direct evidence for the radiative decay of neutron-unbound states in this nucleus. The ability of electromagnetic decay to compete successfully with neutron emission at energies as high as 3 MeV above threshold is attributed to a mismatch between the wave functions of the initial and final states in the latter case. These findings suggest that in the region southeast of ^{132}Sn nuclear structure effects may play a significant role in the neutron versus γ competition in the decay of unbound states. As a consequence, the common neglect of such effects in the evaluation of the neutron-emission probabilities in calculations of global β-decay properties for astrophysical simulations may have to be reconsidered.
Published: 2017
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39. 94 β-Decay Half-Lives of Neutron-Rich _{55}Cs to _{67}Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation.

Author: Wu J, Nishimura S, Lorusso G, Möller P, Ideguchi E, Regan PH, Simpson GS, Söderström PA, Walker PM, Watanabe H, Xu ZY, Baba H, Browne F, Daido R, Doornenbal P, Fang YF, Gey G, Isobe T, Lee PS, Liu JJ, Li Z, Korkulu Z, Patel Z, Phong V, Rice S, Sakurai H, Sinclair L, Sumikama T, Tanaka M, Yagi A, Ye YL, Yokoyama R, Zhang GX, Alharbi T, Aoi N, Bello Garrote FL, Benzoni G, Bruce AM, Carroll RJ, Chae KY, Dombradi Z, Estrade A, Gottardo A, Griffin CJ, Kanaoka H, Kojouharov I, Kondev FG, Kubono S, Kurz N, Kuti I, Lalkovski S, Lane GJ, Lee EJ, Lokotko T, Lotay G, Moon CB, Nishibata H, Nishizuka I, Nita CR, Odahara A, Podolyák Z, Roberts OJ, Schaffner H, Shand C, Taprogge J, Terashima S, Vajta Z, and Yoshida S
Abstract: The β-decay half-lives of 94 neutron-rich nuclei ^{144-151}Cs, ^{146-154}Ba, ^{148-156}La, ^{150-158}Ce, ^{153-160}Pr, ^{156-162}Nd, ^{159-163}Pm, ^{160-166}Sm, ^{161-168}Eu, ^{165-170}Gd, ^{166-172}Tb, ^{169-173}Dy, ^{172-175}Ho, and two isomeric states ^{174m}Er, ^{172m}Dy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for _{58}Ce, _{59}Pr, _{60}Nd, and _{62}Sm, and N=105 for _{63}Eu, _{64}Gd, _{65}Tb, and _{66}Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.
Published: 2017
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