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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. 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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4. Investigation of the Δn = 0 selection rule in Gamow-Teller transitions: The β-decay of 207Hg

Author

T.A. Berry, Zs. Podolyák, R.J. Carroll, R. Lică, H. Grawe, N.K. Timofeyuk, T. Alexander, A.N. Andreyev, S. Ansari, M.J.G. Borge, J. Creswell, C. Fahlander, L.M. Fraile, H.O.U. Fynbo, W. Gelletly, R.-B. Gerst, M. Górska, A. Gredley, P. Greenlees, L.J. Harkness-Brennan, M. Huyse, S.M. Judge, D.S. Judson, J. Konki, J. Kurcewicz, I. Kuti, S. Lalkovski, I. Lazarus, M. Lund, M. Madurga, N. Mărginean, R. Mărginean, I. Marroquin, C. Mihai, R.E. Mihai, E. Nácher, S. Nae, A. Negret, C. Niţă, R.D. Page, S. Pascu, Z. Patel, A. Perea, V. Pucknell, P. Rahkila, E. Rapisarda, P.H. Regan, F. Rotaru, C.M. Shand, E.C. Simpson, Ch. Sotty, S. Stegemann, T. Stora, O. Tengblad, A. Turturica, P. Van Duppen, V. Vedia, R. Wadsworth, P.M. Walker, N. Warr, F. Wearing, and H. De Witte

Subjects
Physics, QC1-999
Abstract

Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn=0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N>82) and Z=82 (for N>126). The level of forbiddenness of the Δn=1ν1g9/2→π0g7/2 transition has been investigated from the β− decay of the ground state of 207Hg into the single-proton-hole nucleus 207Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g7/2−1 state in 207Tl, an upper limit of 3.9×10−3% was obtained for the probability of this decay, corresponding to log⁡ft>8.8 within a 95% confidence limit. This is the most stringent test of the Δn=0 selection rule to date.

Published
2019
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5. 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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6. 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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7. 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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8. Angular momentum generation in nuclear fission

Author

B. Fornal, M. S. Yavahchova, C. Delafosse, A. Boso, V. Sánchez-Tembleque, K. Rezynkina, M. Lebois, K. Hauschild, T. Kröll, Muriel Fallot, P. Adsley, J. Ljungvall, Ł. W. Iskra, F. Ibrahim, E. Adamska, C. Henrich, A. Gottardo, Stephan Oberstedt, R. Chakma, C. Sürder, V. Guadilla, C. Porzio, P. H. Regan, J. Benito, A. Korgul, R. Lozeva, L. Le Meur, M. Piersa, P. Ivanov, V. Vedia, J. Nemer, B. Wasilewska, N. Jovančević, Y. Popovitch, W. Paulsen, C. Schmitt, N. Cieplicka-Oryńczak, R. B. Gerst, Sunniva Siem, G. Tocabens, P. A. Söderström, K. Belvedere, S. Courtin, S. Ziliani, R. Canavan, D. Gjestvang, L. Qi, D. Etasse, P. Koseoglou, G. Häfner, I. Matea, I. Homm, M. Heine, L. M. Fraile, T. Kurtukian-Nieto, Fabio Zeiser, P. Davies, D. Thisse, M. L. Cortés, A. Blazhev, S. Jazrawi, M. Bunce, A. Lopez-Martens, K. Miernik, Alejandro Algora, M. Rudigier, J. N. Wilson, N. Warr, J. Wiederhold, D. Verney, D. Ralet, M. Babo, L. Gaudefroy, G. Benzoni, S. Bottoni, S. Leoni, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Oslo (UiO), Department of Physics, University of Surrey, University of Surrey (UNIS), Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt), 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), CEA, Bruyeres le Chatel, France, affiliation inconnue, University of Warsaw (UW), Facultat de Fisica [València] (UV), Universitat de València (UV), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Università degli Studi di Milano = University of Milan (UNIMI), Institut für Kernphysik der Universität zu Köln, Universität zu Köln = University of Cologne, National Physical Laboratory [Teddington] (NPL), Instytut Fizyki Jądrowej PAN (IFJ), Polskiej Akademii Nauk, Institut Pluridisciplinaire Hubert Curien (IPHC), 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 - Institute of Physical and Chemical Research [Japon] (RIKEN), University of Manchester [Manchester], Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN, Sezione di Padova), Istituto Nazionale di Fisica Nucleare (INFN), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), 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), European Commission - Joint Research Centre [Geel] (JRC), 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), Horia Hulubei Natl Inst Phys & Nucl Engn IFIN HH, ELI NP Dept, Reactorului Str 30, Magurele 077125, Romania, Софийски университет = Sofia University, Technische Universität Darmstadt (TU Darmstadt), Universidad Complutense de Madrid [Madrid] (UCM), Università degli studi di Milano [Milano], Universität zu Köln, Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Technical University Darmstadt (TU), 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), 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), University of Sofia, Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Università degli Studi di Milano [Milano] (UNIMI), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Direction des Applications Militaires (DAM), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Physics, [PHYS]Physics [physics], Angular momentum, Multidisciplinary, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Spins, 010308 nuclear & particles physics, Fission, Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Nuclear physics, Nuclear fission, 0103 physical sciences, Atomic nucleus, Nuclear Experiment, 010306 general physics, Nucleon, Excitation, ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract

When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning1; this phenomenon has been a mystery in nuclear physics for over 40 years2,3. The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum4–12. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors13,14, for the study of the structure of neutron-rich isotopes15,16, and for the synthesis and stability of super-heavy elements17,18. γ-ray spectroscopy experiments on the origin of spin in the products of nuclear fission of spin-zero nuclei suggest that the fission fragments acquire their spin after scission, rather than before.

Published
2021
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9. Lifetime measurements in $^{182}\hbox {Pt}$ using $\gamma $–$\gamma $ fast-timing

Author

L. Knafla, J.-M. Régis, N. Saed-Samii, C. Müller-Gatermann, C. Fransen, A. Esmaylzadeh, V. Karayonchev, A. Blazhev, R.-B. Gerst, J. Jolie, K. O. Zell, G. Häfner, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Hadron, State (functional analysis), Scintillator, Tandem accelerator, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Excited state, 0103 physical sciences, Nuclear fusion, Atomic physics, 010306 general physics, Beam energy, Mixing (physics)
Abstract

The level lifetimes of the $$2_1^+$$ 2 1 + and $$4_1^+$$ 4 1 + states in $$^{182}\hbox {Pt}$$ 182 Pt have been re-measured employing the $$\gamma $$ γ –$$\gamma $$ γ fast-timing technique using fast $$\hbox {LaBr}_3$$ LaBr 3 (Ce) scintillators. Excited states in the nucleus of interest were populated by the fusion-evaporation reaction $$^{170}\hbox {Yb}(^{16}\hbox {O},\hbox {4n})^{182}\hbox {Pt}$$ 170 Yb ( 16 O , 4n ) 182 Pt at a beam energy of 87 MeV provided by the FN Tandem accelerator of the University of Cologne. The lifetime of the $$2_1^+$$ 2 1 + state was re-measured with high accuracy to be $$\tau = 563(12)~$$ τ = 563 ( 12 ) ps and resolves inconsistencies from previous measurements. Experimental results are compared to theoretical calculations in the framework of the sd-IBM with and without configuration mixing.

Published
2021
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10. 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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11. First lifetime investigations of $N>82$ iodine isotopes: The quest for collectivity

Author

A. Korgul, J. Wiederhold, Th. Kröll, S. Leoni, P. Adsley, Muriel Fallot, M. Babo, J. Benito, G. Benzoni, V. Vedia, K. Miernik, L. Qi, J. Nemer, V. Guadilla, C. Sürder, S. Bottoni, D. Verney, S. Jazwari, N. Warr, A. Boso, K. Rezynkina, D. Ralet, J. Ljungvall, F. Ibrahim, L. M. Fraile, T. Kurtukian-Nieto, M. Lebois, Fabio Zeiser, R. Chakma, A. Blazhev, P. H. Regan, R. Lozeva, C. Schmitt, L. Matthieu, R.L. Canavan, M. Piersa-Siłkowska, A. Algora, N. Jovančević, J. N. Wilson, Y. Popovitch, N. Cieplicka-Oryńczak, W. Paulsen, E. Adamska, G. Tocabens, P. Davies, K. Belvedere, D. Gjestvang, S. M. Collins, S. Ziliani, D. Etasse, M. Bunce, C. Henrich, R. B. Gerst, A. Lopez-Martens, M. Rudigier, Ł. W. Iskra, G. Häfner, B. Wasilewska, Stephan Oberstedt, C. Porzio, P. A. Söderström, C. Delafosse, V. Sánchez-Tembleque, L. Le-meur, H. Naïdja, M. S. Yavahchova, P. Koseoglou, I. Homm, D. Thisse, M. L. Cortés, D. Reygadas Tello, K. Hauschild, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-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)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), 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), 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 Laue-Langevin (ILL), Institut Pluridisciplinaire Hubert Curien (IPHC), 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), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), 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), 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), ILL, and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Isotope, 010308 nuclear & particles physics, Fission, chemistry.chemical_element, Context (language use), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Iodine, 01 natural sciences, chemistry, Excited state, 0103 physical sciences, Neutron source, Física nuclear, Atomic physics, 010306 general physics
Abstract

International audience; We report on spectroscopic information and lifetime measurements in the neutron-rich I135,137,139 isotopes. This is the first lifetime data on iodine isotopes beyond N=82. Excited states were populated in fast neutron-induced fission of U238 at the ALTO facility of IJCLab with the LICORNE neutron source and detected using the hybrid ν-ball spectrometer. The level schemes of the I135,137,139 isotopes are revised in terms of excited states with up to maximum spin-parity of (33/2+), populated for the first time in fast neutron-induced fission. We provide first results on the lifetimes of the (9/21+) and (13/21+) states in I137 and I139, and the (17/21+) state in I137. In addition, we give upper lifetime limits for the (11/21+) states in I135−139, the (15/21+) state in I137, the (17/21+) state in I139, and reexamine the (29/21+) state in I137. The isomeric data in I135 are reinvestigated, such as the previously known (15/21+) and (23/21−) isomers with T1/2 of 1.64(14) and 4.6(7) ns, respectively, as obtained in this work. The new spectroscopic information is compared to that from spontaneous or thermal-neutron induced fission and discussed in the context of large scale shell-model (LSSM) calculations for the region beyond Sn132, indicating the behavior of collectivity for the three valence-proton iodine chain with N=82,84,86.

Published
2021
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12. 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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13. $\gamma$-ray Spectroscopy of $^{85}$Se Produced in $^{232}$Th Fission

Author

I. Homm, M. Ciemała, Stephan Oberstedt, K. Rezynkina, P. A. Söderström, B. Fornal, A. Lopez-Martens, M. Bunce, V. Vedia, D. Verney, J. N. Wilson, J. Nemer, B. Wasilewska, A. Algora, M. Babo, R. B. Gerst, L. M. Fraile, Y. Popovitch, R. Chakma, T. Kurtukian-Nieto, Ł. W. Iskra, W. Paulsen, E. Adamska, D. Ralet, G. Häfner, M. Piersa, G. Benzoni, M. Rudigier, A. Fijałkowska, A. Blazhev, S. Leoni, D. Reygadas Tello, K. Hauschild, P. H. Regan, M. S. Yavahchova, J. Wiederhold, V. Guadilla, N. Warr, C. Delafosse, C. Schmitt, R.L. Canavan, V. Sánchez-Tembleque, K. Miernik, R. Lozeva, I. Matea, P. Davies, Muriel Fallot, N. Jovančević, S. Bottoni, M. Lebois, N. Cieplicka-Oryńczak, P. Adsley, C. Henrich, G. Tocabens, K. Belvedere, D. Gjestvang, T. Kröll, L. Cortes, C. Sürder, L. Qi, S. M. Collins, D. Etasse, M. Heine, Fabio Zeiser, A. Boso, F. Ibrahim, J. Benito, A. Korgul, J. Ljungvall, D. Thisse, L. Le-meur, A. Gottardo, P. Koseoglou, 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), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), 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), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), 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), 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), 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), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), 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), 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
Physics, Spectrometer, Isotope, 010308 nuclear & particles physics, Fission, Yrast, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Aucun, General Physics and Astronomy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Nuclear physics, Excited state, 0103 physical sciences, Neutron source, Gamma spectroscopy, Nuclear Experiment
Abstract

International audience; Excited states in the neutron-rich 85Se nucleus have been studied using for the first time a fast neutron-induced fission of 232Th. The experiment was performed at the ALTO facility of the IPN Orsay. Coupling of the LICORNE directional neutron source with the ν-ball high-resolution γ-ray spectrometer provided unique access to high-spin states in neutron-rich fission fragments from the 232Th(n, f) reaction. A preliminary level scheme of 85Se was established by the analysis of prompt γ–γ–γ coincidences. Identification of the all known yrast states in 85Se is the first step towards studies of more neutron-rich Se isotopes.

Published
2019
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14. Lifetime measurement around $^{132}$Sn with the ν-Ball array

Author

G Häfner, R Lozeva, A Blazhev, R L Canavan, D Etasse, J Jolie, N Jovancevic, R B Gerst, Th Kröll, M Lebois, P H Regan, M Rudigier, D Thisse, N Warr, J N Wilson, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), 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), 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), 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, [PHYS]Physics [physics], History, Scintillation, Spectrometer, Fission, Nuclear Theory, Actinide, 01 natural sciences, 010305 fluids & plasmas, Computer Science Applications, Education, Nuclear physics, 0103 physical sciences, Electromagnetic shielding, Neutron source, Neutron, 010306 general physics, Spectroscopy, Nuclear Experiment
Abstract

Neutron-rich nuclei were studied after fast neutron-induced fission of 238U and 232Th at the ALTO facility in Orsay, France. The neutrons were produced with the LICORNE directional neutron source using a pulsed 7Li beam provided by the Tandem accelerator. The actinide targets were surrounded by the ν-Ball array to measure the de-excitation of fission fragments. The ν-Ball array is a hybrid spectrometer which consists of HPGe detectors (equipped with BGO shielding) and LaBr3(Ce) scintillation detectors allowing for high-resolution γ-ray spectroscopy and lifetime measurements in the ns/sub-ns range. This contribution presents preliminary results on 134Te and 137I populated in the 238U(n,f) reaction.

Published
2019
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15. Spectroscopy of Neutron Induced Reactions with the $\nu $-ball Spectrometer

Author

S. Bottoni, M. Lebois, L. Qi, D. Reygadas Tello, R. Shearman, I. Homm, R. B. Gerst, J. N. Wilson, T. Kröll, D. Verney, A. Boso, A. Oberstedt, I. Matea, P. Koseoglou, P. A. Söderström, M. Babo, G. Häfner, M. Piersa, D. Thisse, B. Fornal, M. Rudigier, V. Sanchez, J. Wiederhold, C. Henrich, P. H. Regan, A. Lopez-Martens, F. Ibrahim, K. Miernik, J. Ljungvall, N. Cieplicka-Oryńczak, M. Diakaki, P. Inavov, A. Algora, C. Delafosse, N. Warr, G. Tocabens, J. Benito Garcia, K. Belvedere, S. Leoni, Y. Popovitch, Muriel Fallot, J. Nemer, K. Rezynkina, W. Paulson, C. Sürder, M. Bunce, D. Gestvang, D. Knezevic, V. Guadilla-Gomez, K. Hauschild, Zs. Podolyák, L. Cortes, D. Ralet, A. Gottardo, A. Dragic, E. Adamska, G. Benzoni, R. Lozeva, R. Chakma, N. Jovančević, S. Oberstedt, R. Canavan, F. Adsley, P. Davies, M. Yavachova, C. Schmitt, M. Heine, Fabio Zeiser, D. Etasse, L. M. Fraile, T. Kurtukian-Nieto, A. Blazhev, L. Iskra, 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), Université Paris-Saclay, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), 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), 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), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), 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), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes - Faculté des Sciences et des Techniques, and Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique)

Subjects
Physics, education.field_of_study, Spectrometer, 010308 nuclear & particles physics, Fission, Astrophysics::High Energy Astrophysical Phenomena, Population, Aucun, General Physics and Astronomy, Shields, chemistry.chemical_element, Germanium, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, chemistry, 0103 physical sciences, Neutron source, Neutron, Atomic physics, 010306 general physics, education, Spectroscopy, Nuclear Experiment
Abstract

The ʋ-ball is a high-efficiency hybrid spectrometer which consists of both germanium (Ge) detectors and associated anti-Compton BGO shields, coupled to lanthanum bromide (LaBr3) detectors. The hybrid configuration provides a combination of both excellent energy and timing resolutions. The ʋ-ball geometry allows the coupling with the LICORNE directional neutron source at the ALTO facility of the IPN, Orsay. This opens the possibility to perform precise spectroscopy of neutron induced reactions and was used for two experiments during the recent experimental campaign. These two experiments are described here: 1. Spectroscopy of the neutron-rich fission fragments produced in the 238U(n; f) and 232Th(n; f) reactions; 2. Spectroscopy above the shape isomer in 238U. The 238U(n; f) and 232Th(n; f) reactions produce hundreds of neutron-rich nuclei on which gamma-ray spectroscopy can be performed. The main goal of the experiment aiming to populate the shape isomer in 238U is the measurement of the gamma-ray and fission decay branches as well as determination of level scheme in the super-deformed minimum. The shape isomer is populated by 238U(n; n') reaction, which gives a very advantageous population cross section over other reactions. More detailed descriptions of these two ʋ-ball experiments will be presented here.

Published
2019
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