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43 results on '"Ł. W. Iskra"'

1. Characterization of Diamond and Silicon Carbide Detectors With Fission Fragments

Author

M. L. Gallin-Martel, Y. H. Kim, L. Abbassi, A. Bes, C. Boiano, S. Brambilla, J. Collot, G. Colombi, T. Crozes, S. Curtoni, D. Dauvergne, C. Destouches, F. Donatini, L. Gallin-Martel, O. Ghouini, J. Y. Hostachy, Ł. W. Iskra, M. Jastrzab, G. Kessedjian, U. Köster, A. Lacoste, A. Lyoussi, S. Marcatili, J. F. Motte, J. F. Muraz, T. Nowak, L. Ottaviani, J. Pernot, A. Portier, W. Rahajandraibe, M. Ramdhane, M. Rydygier, C. Sage, A. Tchoualack, L. Tribouilloy, and M. Yamouni

Subjects
solid-state detectors, diamond detectors, silicon carbide detectors, heavy-ion detectors, radiation-hard detectors, fission fragment, Physics, QC1-999
Abstract

Experimental fission studies for reaction physics or nuclear spectroscopy can profit from fast, efficient, and radiation-resistant fission fragment (FF) detectors. When such experiments are performed in-beam in intense thermal neutron beams, additional constraints arise in terms of target-detector interface, beam-induced background, etc. Therefore, wide gap semi-conductor detectors were tested with the aim of developing innovative instrumentation for such applications. The detector characterization was performed with mass- and energy-separated fission fragment beams at the ILL (Institut Laue Langevin) LOHENGRIN spectrometer. Two single crystal diamonds, three polycrystalline and one diamond-on-iridium as well as a silicon carbide detector were characterized as solid state ionization chamber for FF detection. Timing measurements were performed with a 500-µm thick single crystal diamond detector read out by a broadband amplifier. A timing resolution of ∼10.2 ps RMS was obtained for FF with mass A = 98 at 90 MeV kinetic energy. Using a spectroscopic preamplifier developed at INFN-Milano, the energy resolution measured for the same FF was found to be slightly better for a ∼50-µm thin single crystal diamond detector (∼1.4% RMS) than for the 500-µm thick one (∼1.6% RMS), while a value of 3.4% RMS was obtained with the 400-µm silicon carbide detector. The Pulse Height Defect (PHD), which is significant in silicon detectors, was also investigated with the two single crystal diamond detectors. The comparison with results from α and triton measurements enabled us to conclude that PHD leads to ∼50% loss of the initial generated charge carriers for FF. In view of these results, a possible detector configuration and integration for in-beam experiments has been discussed.

Published
2021
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3. Decay of the 'stretched' M4 resonance in 13C

Author

D.A. Iancu, P. Kulessa, L. Stan, Y. Jaganathen, S. Bottoni, A. Maj, N. Marginean, Michele Sferrazza, S. Brambilla, P. Pawłowski, S. Ziliani, A. Bracco, M. Kmiecik, J. Łukasik, Ł. W. Iskra, B. Fornal, K. Mazurek, I. Burducea, S. Leoni, C. Boiano, R. Marginean, N. Florea, C. Clisu, F. Camera, B. Sowicki, M. Płoszajczak, M.N. Harakeh, N. Cieplicka-Oryńczak, M. Krzysiek, M. Ciemala, M. Zieblinski, J. Grebosz, B. Wasilewska, M. Matejska-Minda, 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Research unit Nuclear & Hadron Physics

Subjects
Physics, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Proton, Nuclear Theory, Continuum (design consultancy), Cyclotron, SHELL model, General Physics and Astronomy, Resonance (particle physics), Coincidence, law.invention, Nuclear physics, law, Neutron, Nuclear Experiment
Abstract

International audience; “Stretched” states are examples of the simplest nuclear excitations in the continuum, thus offering an excellent testing ground for various theoretical approaches. The decay of the stretched single-particle state in 13C, located at 21.47 MeV, was investigated in an experiment performed recently at the Cyclotron Centre Bronowice (CCB) at IFJ PAN in Kraków. First experimental information on the proton and neutron decay channels of this resonance was obtained by employing coincidence measurement of protons inelastically scattered on the 13C target and γ rays from daughter nuclei. The new experimental findings will be used for testing predictions obtained by the Gamow Shell Model calculations.

Published
2020

4. γ decay to the ground state from the excitations above the neutron threshold in the Pb208(p,p′γ) reaction at 85 MeV

Author

B. Wasilewska, M. Kmiecik, M. Ciemała, A. Maj, F. C. L. Crespi, A. Bracco, M. N. Harakeh, P. Bednarczyk, S. Bottoni, S. Brambilla, F. Camera, I. Ciepał, N. Cieplicka-Oryńczak, M. Csatlos, B. Fornal, V. Gaudilla, J. Grȩbosz, J. Isaak, Ł. W. Iskra, M. Jeżabek, A. J. Krasznahorkay, S. Kihel, M. Krzysiek, P. Lasko, S. Leoni, M. Lewitowicz, J. Łukasik, M. Matejska-Minda, K. Mazurek, P. J. Napiorkowski, W. Parol, P. Pawłowski, L. Q. Qi, M. Saxena, Ch. Schmitt, Y. Sobolev, B. Sowicki, M. Stanoiu, A. Tamii, O. Wieland, and M. Ziȩbliński

Published
2022

5. Complete set of bound negative-parity states in the neutron-rich nucleus 18N

Author

S. Ziliani, M. Ciemała, F. C. L. Crespi, S. Leoni, B. Fornal, T. Suzuki, T. Otsuka, A. Maj, P. Bednarczyk, G. Benzoni, A. Bracco, C. Boiano, S. Bottoni, S. Brambilla, M. Bast, M. Beckers, T. Braunroth, F. Camera, N. Cieplicka-Oryńczak, E. Clément, S. Coelli, O. Dorvaux, S. Erturk, G. de France, C. Fransen, A. Goldkuhle, J. Grębosz, M. N. Harakeh, Ł. W. Iskra, B. Jacquot, A. Karpov, M. Kicińska-Habior, Y. Kim, M. Kmiecik, A. Lemasson, S. M. Lenzi, M. Lewitowicz, H. Li, I. Matea, K. Mazurek, C. Michelagnoli, M. Matejska-Minda, B. Million, C. Müller-Gatermann, V. Nanal, P. Napiorkowski, D. R. Napoli, R. Palit, M. Rejmund, Ch. Schmitt, M. Stanoiu, I. Stefan, E. Vardaci, B. Wasilewska, O. Wieland, M. Ziębliński, M. Zielińska, 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), 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), Institut Laue-Langevin (ILL), ILL, 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Set (abstract data type), Physics, Particle physics, medicine.anatomical_structure, 010308 nuclear & particles physics, 0103 physical sciences, medicine, Neutron, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 010306 general physics, Parity (mathematics), 01 natural sciences, Nucleus
Abstract

International audience; High-resolution γ-ray spectroscopy of N18 is performed with the Advanced GAmma Tracking Array, following deep-inelastic processes induced by an O18 beam on a Ta181 target. Six states are newly identified, which together with the three known excitations exhaust all negative-parity excited states expected in N18 below the neutron threshold. Spin and parities are proposed for all located states on the basis of decay branchings and comparison with large-scale shell-model calculations performed in the p-sd space, with the YSOX interaction. Of particular interest is the location of the 01− and 12− excitations, which provide strong constrains for cross-shell p-sd matrix elements based on realistic interactions and help to simultaneously reproduce the ground and first-excited states in N16 and N18, for the first time. Understanding the N18 structure may also have significant impact on neutron-capture cross-section calculations in r-process modeling including light neutron-rich nuclei.

Published
2021

6. Revised B(E3) transition rate and structure of the 3− level in 96Zr

Author

T. Lauritsen, M. P. Carpenter, R. Broda, Takaharu Otsuka, R. V. F. Janssens, Ł. W. Iskra, T. Togashi, W. B. Walters, Yusuke Tsunoda, B. Fornal, and S. Zhu

Subjects
Physics, Nuclear and High Energy Physics, Proton, 010308 nuclear & particles physics, Monte Carlo method, Structure (category theory), Transition rate matrix, 01 natural sciences, lcsh:QC1-999, Character (mathematics), Atomic orbital, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, lcsh:Physics, Line (formation)
Abstract

The B(E3) transition strength from the 1897-keV, 3− level in 96Zr has been reevaluated from six high-statistics, independent data sets. The measured value of 42(3) W.u. is significantly lower than that adopted in recent compilations. It is, however, in line with the global systematics of collective B(E3) rates found throughout the periodic table. Thus, the “exceptional” character of this transition, that challenged theory, no longer applies. Monte Carlo shell-model calculations indicate that the collectivity of the octupole vibration arises from both proton and neutron excitations involving a large number of orbitals. Keywords: 90≤A≤149, 3− level, Octupole excitation, Lifetimes and branching ratios, B(E3) strength, Monte Carlo shell model calculations

Published
2019

7. Accessing tens-to-hundreds femtoseconds nuclear state lifetimes with low-energy binary heavy-ion reactions

Author

M. Zieblinski, J. Grebosz, K. Mazurek, Simone Coelli, S. Brambilla, H. J. Li, B. Million, M. Rejmund, Bertrand Jacquot, P. Bednarczyk, N. Cieplicka-Oryńczak, M. Ciemala, M. Bast, S. Ziliani, O. Dorvaux, S. Erturk, Eric Clément, Ł. W. Iskra, C. Fransen, S. M. Lenzi, B. Fornal, P. J. Napiorkowski, C. Müller-Gatermann, M. Zielińska, B. Wasilewska, I. Matea, A. Maj, M. Kmiecik, Y. H. Kim, M. Kicińska-Habior, C. Michelagnoli, I. Stefan, M. Beckers, F. C. L. Crespi, O. Wieland, M. Lewitowicz, R. Palit, D. R. Napoli, Ch. Schmitt, A. V. Karpov, M. Stanoiu, F. Camera, Emanuele Vardaci, M. Matejska-Minda, A. Bracco, G. Benzoni, S. Bottoni, S. Leoni, V. Nanal, C. Boiano, A. Lemasson, Mohsen Harakeh, Thomas Braunroth, A. Goldkuhle, 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), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), ILL, 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Ciemala, M., Ziliani, S., Crespi, F. C. L., Leoni, S., Fornal, B., Maj, A., Bednarczyk, P., Benzoni, G., Bracco, A., Boiano, C., Bottoni, S., Brambilla, S., Bast, M., Beckers, M., Braunroth, T., Camera, F., Cieplicka-Orynczak, N., Clement, E., Coelli, S., Dorvaux, O., Erturk, S., De France, G., Fransen, C., Goldkuhle, A., Grebosz, J., Harakeh, M. N., Iskra, L. W., Jacquot, B., Karpov, A., Kicinska-Habior, M., Kim, Y. -H., Kmiecik, M., Lemasson, A., Lenzi, S. M., Lewitowicz, M., Li, H., Matea, I., Mazurek, K., Michelagnoli, C., Matejska-Minda, M., Million, B., Muller-Gatermann, C., Nanal, V., Napiorkowski, P., Napoli, D. R., Palit, R., Rejmund, M., Schmitt, C., Stanoiu, M., Stefan, I., Vardaci, E., Wasilewska, B., Wieland, O., Zieblinski, M., Zielinska, M., H. Niewodniczanski Institute of Nuclear Physics, Polska Akademia Nauk = Polish Academy of Sciences (PAN), Dipartimento di Fisica (Milano), Università degli Studi di Milano [Milano] (UNIMI), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Institut für Kernphysik der Universität zu Köln, Universität zu Köln, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Milano = University of Milan (UNIMI), Universität zu Köln = University of Cologne, 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), 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 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 Nuclear Energy

Subjects
Nuclear reaction, Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Monte Carlo method, Hadron, FOS: Physical sciences, Binary number, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Excited state, 0103 physical sciences, Nuclear fusion, AGATA, Nuclear Experiment (nucl-ex), Connection (algebraic framework), Atomic physics, Nuclear Experiment, 010306 general physics
Abstract

A novel Monte Carlo technique has been developed to determine lifetimes of excited states in the tens-to-hundreds femtoseconds range in products of low-energy heavy-ion binary reactions, with complex velocity distributions. The method is based on a detailed study of Doppler-broadened $$\gamma $$ γ -ray lineshapes. Its relevance is demonstrated in connection with the $$^{18}\text {O}(7.0\, \text {MeV/u})+\,^{181}\text {Ta}$$ 18 O ( 7.0 MeV/u ) + 181 Ta experiment, performed at GANIL with the AGATA+VAMOS+PARIS setup, to study neutron-rich O, C, N, ... nuclei. Excited states in $$^{17}\text {O}$$ 17 O and $$^{19}\text {O}$$ 19 O , with known lifetimes, are used to validate the method over the $$\sim 20{-}400\,\text {fs}$$ ∼ 20 - 400 fs lifetime-sensitivity range. Emphasis is given to the unprecedented position resolution provided by $$\gamma $$ γ -tracking arrays, which turns out to be essential for reaching the required accuracy in Doppler-shift correction. The technique is anticipated to be an important tool for lifetime investigations in exotic neutron-rich nuclei, produced with intense ISOL-type beams.

Published
2021

8. Spectroscopy and lifetime measurements in Te134,136,138 isotopes and implications for the nuclear structure beyond N=82

Author

D. Verney, D. Ralet, J. Wiederhold, S. Bottoni, L. Matthieu, B. Fornal, A. Blazhev, P. H. Regan, C. Schmitt, R.L. Canavan, K. Rezynkina, D. Reygadas Tello, A. Lopez-Martens, K. Hauschild, B. Wasilewska, I. Matea, A. Korgul, C. Henrich, J. Jolie, V. Guadilla, M. Lebois, M. Babo, Th. Kröll, L. M. Fraile, J. Benito, G. Benzoni, T. Kurtukian-Nieto, L. Qi, Stephan Oberstedt, C. Porzio, M. Bunce, N. Warr, R. B. Gerst, P. A. Söderström, Y. Popovitch, W. Paulsen, F. Ibrahim, Ł. W. Iskra, G. Häfner, J. N. Wilson, S. Jazwari, M. S. Yavahchova, R. Chakma, C. Delafosse, A. Boso, R. Lozeva, N. Jovančević, V. Sanchez, H. Naïdja, M. Rudigier, P. Adsley, L. Le-meur, N. Cieplicka-Oryńczak, I. Homm, E. Adamska, G. Tocabens, K. Belvedere, D. Gjestvang, D. Thisse, M. L. Cortés, P. Koseoglou, P. Davies, V. Vedia, J. Nemer, M. Piersa, Muriel Fallot, C. Sürder, K. Miernik, S. M. Collins, S. Ziliani, D. Etasse, Fabio Zeiser, and J. Ljungvall

Subjects
Physics, Spectrometer, Isotope, 010308 nuclear & particles physics, Fission, Nuclear structure, Context (language use), 7. Clean energy, 01 natural sciences, Excited state, 0103 physical sciences, Neutron source, Atomic physics, 010306 general physics, Spectroscopy
Abstract

We report on spectroscopic information and lifetime measurements of even-even neutron-rich Te isotopes. 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. We provide first results on lifetimes of the 61+ state in Te136 and the (61+), (41+), and (21+) states in Te138 and discuss the results in the context of large-scale shell-model calculations. The level schemes of Te136 and Te138 are revised in terms of lifetimes of their 21+,41+ states and updated information on the (42+) state in Te136 is presented. In addition, previously reported data on spectroscopy and lifetimes in Te134 are reexamined. This work provides new insights into the evolution of collectivity for Te isotopes with N=82,84,86.

Published
2021

9. 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

10. Low-spin particle-core and hole-core excitations in Ca41,47,49 isotopes studied by cold-neutron-capture reactions

Author

S. Bottoni, N. Cieplicka-Oryńczak, S. Leoni, B. Fornal, G. Colò, P. F. Bortignon, G. Bocchi, D. Bazzacco, G. Benzoni, A. Blanc, A. Bracco, S. Ceruti, F. C. L. Crespi, G. de France, E. R. Gamba, Ł. W. Iskra, M. Jentschel, U. Köster, C. Michelagnoli, B. Million, D. Mengoni, P. Mutti, Y. Niu, C. Porzio, G. Simpson, T. Soldner, B. Szpak, A. Türler, C. A. Ur, and W. Urban

Subjects
Physics, Isotope, 010308 nuclear & particles physics, Phonon, Astrophysics::High Energy Astrophysical Phenomena, Large array, 01 natural sciences, Neutron capture, symbols.namesake, 0103 physical sciences, symbols, Atomic physics, 010306 general physics, Hpge detector, Hamiltonian (quantum mechanics)
Abstract

We present recent results on the structure of the one-valence-particle $^{41}$Ca and $^{49}$Ca, and one-valence-hole $^{47}$Ca, nuclei. The isotopes of interest were populated via the cold-neutron capture reactions $^{40}$Ca(n,$\gamma$), $^{48}$Ca(n,$\gamma$) and $^{46}$Ca(n,$\gamma$), respectively. The experiments were performed at the Institut Laue-Langevin, within the EXILL campaign, which employed a large array of HPGe detectors. The $\gamma$ decay and level schemes of these nuclei were investigated by $\gamma$-ray coincidence relationships, leading to the identification of 41, 10, and 6 new transitions in $^{41}$Ca, $^{47}$Ca, and $^{49}$Ca, respectively. Branching ratios and intensities were extracted for the $\gamma$ decay from each state, and $\gamma$-ray angular correlations were performed to establish a number of transition multipolarities and mixing ratios, thus helping in the spin assignment of the states. The experimental findings are discussed along with microscopic, self-consistent beyond-mean-field calculations performed with the Hybrid Configuration Mixing model, based on a Skyrme SkX Hamiltonian. The latter suggests that a fraction of the low-spin states of the $^{41}$Ca, $^{49}$Ca, and $^{47}$Ca nuclei is characterized by the coexistence of either 2p-1h and 1p-2h excitations, or couplings between single-particle/hole degrees of freedom and collective vibrations (phonons) of the doubly-magic "core".

Published
2021

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

12. Prompt and delayed γ spectroscopy of neutron-rich Kr94 and observation of a new isomer

Author

R. Chakma, N. Cieplicka-Oryńczak, P. Adsley, G. Tocabens, Muriel Fallot, K. Belvedere, D. Gjestvang, L. Qi, J. Wiederhold, S. Leoni, C. Sürder, J. Benito, J. N. Wilson, K. Hauschild, R. B. Gerst, Stephan Oberstedt, Ł. W. Iskra, C. Porzio, P. A. Söderström, G. Häfner, M. Rudigier, I. Matea, C. Henrich, D. Verney, R.L. Canavan, K. Miernik, V. Vedia, D. Ralet, J. Nemer, P. Koseoglou, M. Piersa, N. Warr, R. Lozeva, L. Le Meur, A. Algora, M. Lebois, N. Jovančević, K. Rezynkina, S. Jazrawi, A. Blazhev, S. Courtin, M. Bunce, S. Bottoni, P. H. Regan, A. Boso, A. Lopez-Martens, C. Schmitt, B. Fornal, P. Ivanov, B. Wasilewska, L. M. Fraile, F. Ibrahim, M. Babo, T. Kurtukian-Nieto, A. Gottardo, G. Benzoni, T. Kröll, D. Reygadas-Tello, E. Adamska, J. Ljungvall, V. Guadilla, A. Korgul, Y. Popovitch, W. Paulsen, I. Homm, D. Thisse, M. L. Cortés, M. Heine, Fabio Zeiser, C. Delafosse, V. Sánchez-Tembleque, P. Davies, M. Yavachova, S. Ziliani, and D. Etasse

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Fission, Astrophysics::High Energy Astrophysical Phenomena, Yrast, Nuclear Theory, 01 natural sciences, 7. Clean energy, Atomic orbital, Nuclear fission, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Spin (physics), Spectroscopy
Abstract

Prompt and delayed γ -ray spectroscopy of the neutron-rich 94 Kr was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction 238 U ( n , f ) in combination with the ν -Ball array, a novel hybrid γ spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a ( 9 − ) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones 96 Sr and 92 Se

Published
2020

13. Detailed low-spin spectroscopy of 65Ni via neutron capture reaction

Author

F. Kandzia, S. Bottoni, C. Costache, Michele Sferrazza, A. Turturica, Takaharu Otsuka, Ulli Köster, Y.H. Kim, N. Cieplicka-Oryńczak, Ł. W. Iskra, C. Michelagnoli, B. Fornal, C. Porzio, S. Leoni, F. C. L. Crespi, Michael Jentschel, N. Marginean, C. Mihai, Yusuke Tsunoda, Paolo Mutti, Institut Laue-Langevin (ILL), and ILL

Subjects
Physics, Spins, 010308 nuclear & particles physics, Monte Carlo method, FOS: Physical sciences, Généralités, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 3. Good health, Neutron capture, Angular correlation, Excited state, 0103 physical sciences, Oblate spheroid, Nuclear Experiment (nucl-ex), Atomic physics, 010306 general physics, Spin (physics), Spectroscopy, Nuclear Experiment
Abstract

An extended investigation of the low-spin structure of the Ni65 nucleus was performed at the Institut Laue-Langevin, Grenoble, France, via the neutron capture reaction Ni64(n,γ)Ni65, using the Fission Product Prompt Gamma-Ray Spectrometer High-Purity Ge array. The level scheme of Ni65 was significantly expanded, with two new levels and 87 newly found transitions. Angular correlation analyses were also performed, allowing us to assign spins and parities for a number of states and to determine multipolarity mixing ratios for selected γ transitions. The low-energy part of the experimental level scheme (up to about 1.4 MeV) was compared with Monte Carlo shell-model calculations, which predict spherical shapes for all states, apart from the 9/2+ and the second excited 1/2- states of oblate deformation., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2020

14. γ spectroscopy of the Y96 isotope: Searching for the onset of shape coexistence before N=60

Author

Ulli Köster, Y.H. Kim, C. Porzio, J. Dudouet, A. Turturica, Cosmin Teodor Mihai, S. Bottoni, N. Marginean, N. Cieplicka-Oryńczak, D. Reygadas, E. Ruiz-Martinez, R. Lica, Michael Jentschel, S. Pascu, B. Fornal, C. Michelagnoli, Ł. W. Iskra, S. Leoni, R. E. Mihai, M. Barani, R. Mărginean, C. Costache, G. Colombi, F. C. L. Crespi, C. R. Nita, and F. Kandzia

Subjects
Physics, Nuclear fission product, Isotope, Spin states, 010308 nuclear & particles physics, Fission, 01 natural sciences, Spectral line, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Ground state, Spectroscopy
Abstract

Medium and high spin states of the Y96 nucleus, located in the shape-coexistence region near Z=40 and N=60, were populated in thermal-neutron-induced fission of U233 and U235 targets, diluted in a scintillator. γ rays were measured with the FIssion Product Prompt γ-ray Spectrometer (FIPPS) high-purity germanium (HPGe) detector array, using double and triple γ-ray coincidence techniques and taking advantage of the efficient fission tag provided by the scintillating target material. A complex level scheme, extending up to 5.2 MeV and including excitations above the 8+β-decaying isomer, was investigated, and firm spin and parity assignments were given to a number of states, on the basis of angular correlation analysis and considerations on the γ-decay patterns. While the structures built on the 0− ground state and the 8+ isomer show irregular patterns typical for spherical shapes, the (6+) isomeric state at 1655 keV [with half-life of 181(9) ns], and the rotational band built on it [with spin-parity values between (6+) and (9+)], can be explained by Hartree-Fock-Bogoliubov calculations, if an oblate deformation is assumed. This is the first observation of a deformed structure in an N=57 isotone, lying three neutrons away from the N=60 line. An important finding is also the 115-keV transition which connects the (6+) 181(9)-ns isomer to the β-decaying 8+ spherical isomer, allowing us to firmly place the latter at 1541 keV excitation energy. This may be relevant for calculations of electron and antineutrino spectra from fission of actinides, for which Y96 is a prominent product.

Published
2020

15. Shape Coexistence at Zero Spin in ^{64}Ni Driven by the Monopole Tensor Interaction

Author

N, Mărginean, D, Little, Y, Tsunoda, S, Leoni, R V F, Janssens, B, Fornal, T, Otsuka, C, Michelagnoli, L, Stan, F C L, Crespi, C, Costache, R, Lica, M, Sferrazza, A, Turturica, A D, Ayangeakaa, K, Auranen, M, Barani, P C, Bender, S, Bottoni, M, Boromiza, A, Bracco, S, Călinescu, C M, Campbell, M P, Carpenter, P, Chowdhury, M, Ciemała, N, Cieplicka-Oryǹczak, D, Cline, C, Clisu, H L, Crawford, I E, Dinescu, J, Dudouet, D, Filipescu, N, Florea, A M, Forney, S, Fracassetti, A, Gade, I, Gheorghe, A B, Hayes, I, Harca, J, Henderson, A, Ionescu, Ł W, Iskra, M, Jentschel, F, Kandzia, Y H, Kim, F G, Kondev, G, Korschinek, U, Köster, Krishichayan, M, Krzysiek, T, Lauritsen, J, Li, R, Mărginean, E A, Maugeri, C, Mihai, R E, Mihai, A, Mitu, P, Mutti, A, Negret, C R, Niţă, A, Olăcel, A, Oprea, S, Pascu, C, Petrone, C, Porzio, D, Rhodes, D, Seweryniak, D, Schumann, C, Sotty, S M, Stolze, R, Şuvăilă, S, Toma, S, Ujeniuc, W B, Walters, C Y, Wu, J, Wu, S, Zhu, and S, Ziliani

Abstract

The low-spin structure of the semimagic ^{64}Ni nucleus has been considerably expanded: combining four experiments, several 0^{+} and 2^{+} excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0^{+} excitation is located at a surprisingly high energy (3463 keV), with a collective 2^{+} state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.

Published
2020

16. Testing ab initio nuclear structure in neutron-rich nuclei: Lifetime measurements of second 2+ state in C16 and O20

Author

M. Ciemała, S. Ziliani, F. C. L. Crespi, S. Leoni, B. Fornal, A. Maj, P. Bednarczyk, G. Benzoni, A. Bracco, C. Boiano, S. Bottoni, S. Brambilla, M. Bast, M. Beckers, T. Braunroth, F. Camera, N. Cieplicka-Oryńczak, E. Clément, S. Coelli, O. Dorvaux, S. Erturk, G. de France, C. Fransen, A. Goldkuhle, J. Grębosz, M. N. Harakeh, Ł. W. Iskra, B. Jacquot, A. Karpov, M. Kicińska-Habior, Y. Kim, M. Kmiecik, A. Lemasson, S. M. Lenzi, M. Lewitowicz, H. Li, I. Matea, K. Mazurek, C. Michelagnoli, M. Matejska-Minda, B. Million, C. Müller-Gatermann, V. Nanal, P. Napiorkowski, D. R. Napoli, R. Palit, M. Rejmund, Ch. Schmitt, M. Stanoiu, I. Stefan, E. Vardaci, B. Wasilewska, O. Wieland, M. Zieblinski, M. Zielińska, A. Ataç, D. Barrientos, B. Birkenbach, A. J. Boston, B. Cederwall, L. Charles, J. Collado, D. M. Cullen, P. Désesquelles, C. Domingo-Pardo, J. Dudouet, J. Eberth, V. González, J. Goupil, L. J. Harkness-Brennan, H. Hess, D. S. Judson, A. Jungclaus, W. Korten, M. Labiche, A. Lefevre, R. Menegazzo, D. Mengoni, J. Nyberg, R. M. Perez-Vidal, Zs. Podolyak, A. Pullia, F. Recchia, P. Reiter, F. Saillant, M. D. Salsac, E. Sanchis, O. Stezowski, Ch. Theisen, J. J. Valiente-Dobón, J. D. Holt, J. Menéndez, A. Schwenk, and J. Simonis

Subjects
Physics, 010308 nuclear & particles physics, 0103 physical sciences, Nuclear structure, Ab initio, Neutron, State (functional analysis), Atomic physics, 010306 general physics, 7. Clean energy, 01 natural sciences, Nuclear theory
Abstract

To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2(+) state in neutron-rich O-20, tau(2(2)(+)) = 150(-30)(+80) fs, and an estimate for the lifetime of ...

Published
2020

17. Half-life measurements in Dy164,166 using γ−γ fast-timing spectroscopy with the ν -Ball spectrometer

Author

K. Hadynska-Klek, S. Bottoni, Stephan Oberstedt, D. T. Doherty, P. A. Söderström, D. Thisse, R. Shearman, V. Sánchez-Tembleque, V. Vedia, V. Karayonchev, S. Courtin, Zs. Podolyák, Giuseppe Lorusso, J. N. Wilson, G. Häfner, M. Rudigier, C. R. Niţă, M. Lebois, Mohammad Nakhostin, M. Brunet, L. M. Fraile, W. Witt, A. R. L. Kennington, L. Qi, Gavin Lotay, N. Jovancevic, R.L. Canavan, N. Cieplicka-Oryńczak, Ł. W. Iskra, Sean Collins, P. H. Regan, J.-M. Régis, M. Heine, J. Benito, and P. Koseoglou

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Yrast, Nuclear Theory, Gamma ray, Nuclear structure, Coulomb excitation, 01 natural sciences, Excited state, 0103 physical sciences, Quadrupole, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy
Abstract

We report on the measurement of lifetimes of excited states in the near-mid-shell nuclei Dy164,166 using the gamma-ray coincidence fast-timing method. The nuclei of interest were populated using reactions between an O18 beam and a gold-backed isotopically enriched Dy164 target of thickness 6.3mg/cm2 at primary beam energies of 71, 76, and 80 MeV from the IPN-Orsay laboratory, France. Excited states were populated in Dy164, Dy166, and W178,179 following Coulomb excitation, inelastic nuclear scattering, two-neutron transfer, and fusion-evaporation reaction channels respectively. Gamma rays from excited states were measured using the ν-Ball high-purity germanium (HPGe)-LaBr3 hybrid γ-ray spectrometer with the excited state lifetimes extracted using the fast-timing coincidence method using HPGe-gated LaBr3-LaBr3 triple coincident events. The lifetime of the first Iπ=2+ excited state in Dy166 was used to determine the transition quadrupole deformation of this neutron-rich nucleus for the first time. The experimental methodology was validated by showing consistency with previously determined excited state lifetimes in Dy164. The half-lives of the yrast 2+ states in Dy164 and Dy166 were 2.35(6) and 2.3(2) ns, respectively, corresponding to transition quadrupole moment values of Q0=7.58(9) and 7.5(4) eb, respectively. The lifetime of the yrast 2+ state in Dy166 is consistent with a quenching of nuclear quadrupole deformation at β≈0.35 as the N=104 mid-shell is approached.

Published
2020

18. Multi-quasiparticle sub-nanosecond isomers in $^{178}$W

Author

M. Lebois, R. Shearman, M. Brunet, L. Qi, Gavin Lotay, V. Vedia, V. Sánchez-Tembleque, J.-M. Régis, M. Heine, S. Courtin, R. Canavan, Mohammad Nakhostin, Giuseppe Lorusso, D. T. Doherty, Ł. W. Iskra, J. N. Wilson, C. R. Nita, S. Bottoni, V. Karayonchev, N. Cieplicka-Oryńczak, A. R. L. Kennington, Zs. Podolyák, J. Jolie, J. Benito, P. H. Regan, P. Koseoglou, A. Blazhev, P. A. Söderström, L. M. Fraile, P. M. Walker, Stephan Oberstedt, W. Witt, K. O. Zell, N. Jovancevic, K. Hadynska-Klek, M. Rudigier, 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-Sud - Paris 11 (UP11), Institut Pluridisciplinaire Hubert Curien (IPHC), 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 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 Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Detector, Aucun, Calorimetry, Scintillator, Nanosecond, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, lcsh:QC1-999, 3. Good health, 0103 physical sciences, Quasiparticle, ddc:530, Física nuclear, Atomic physics, 010306 general physics, Spectroscopy, lcsh:Physics, Beam (structure), Mixing (physics)
Abstract

We report on the first measurement of the half-lives of K-pi = 11(-) and 12(+) four-quasiparticle states in the even-even nucleus W-178. The sub-nanosecond half-lives were measured by applying the centroid shift method to data taken with LaBr3(Ce) scintillator detectors of the NuBall array at the ALTO facility in Orsay, France. The half-lives of these states only became experimentally accessible by the combination of several experimental techniques - scintillator fast timing, isomer spectroscopy with a pulsed beam, and the event-by-event calorimetry information provided by the NuBall array. The measured half-lives are 476(44)ps and 275(65)ps for the I-pi = 11(-) and 12(+) states, respectively. The decay transitions include weakly hindered E1 and E2 branches directly to the ground-state band, bypassing the two-quasiparticle states. This is the first such observation for an E1 transition. The interpretation of the small hindrance hinges on mixing between the ground-state band and the t-band. (C) 2019 The Author(s). Published by Elsevier B.V.

Published
2020

20. $\gamma$-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

21. Isomer Spectroscopy and Sub-nanosecond Half-live Determination in $^{178}$W Using the NuBALL Array

Author

Mohammad Nakhostin, R.L. Canavan, P. H. Regan, D. T. Doherty, Stephan Oberstedt, S. Bottoni, P. A. Söderström, P. M. Walker, R. Shearman, A. R. L. Kennington, K. Hadynska-Klek, N. Jovancevic, P. Koseoglou, N. Cieplicka-Oryńczak, Gavin Lotay, Giuseppe Lorusso, W. Witt, J. N. Wilson, Ł. W. Iskra, M. Lebois, V. Karayonchev, M. Brunet, Zs. Podolyák, L. Qi, C. R. Nita, S. Courtin, M. Rudigier, J.-M. Régis, M. Heine, 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), Université Paris-Saclay, Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), 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 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, 010308 nuclear & particles physics, Detector, General Physics and Astronomy, Nanosecond, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics, Spectroscopy, Beam (structure)
Abstract

The reaction of a pulsed 18O beam on a 164Dy target was studied in the first experiment with the NuBall array at the IPN Orsay, France. Excited state half-lives were measured using the fast timing method with 20 LaBr3(Ce) detectors. The timing characteristics of the fully digital acquisition system is briefly discussed. A value for the previously unknown half-life of the first excited 4+ state in 178W is presented.

Published
2019
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22. Reaction Channel selection techniques and γ – γ fast-timing spectroscopy using the ν-Ball Spectrometer

Author

V. Karayonchev, L. Qi, C. R. Niţă, Gavin Lotay, Mohammad Nakhostin, Ł. W. Iskra, N. Cieplicka-Oryńczak, A. R. L. Kennington, J.-M. Régis, S. Bottoni, Sean Collins, S. Courtin, P. H. Regan, D. Thisse, V. Vedia, M. Heine, Giuseppe Lorusso, J. N. Wilson, R. Shearman, M. Lebois, Stephan Oberstedt, P. A. Söderström, M. Rudigier, P. Koseoglou, N. Jovančević, W. Witt, J. Benito, M. Brunet, Zs. Podolyák, K. Hadynska-Klek, D. T. Doherty, R.L. Canavan, L. M. Fraile, 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), Institut Pluridisciplinaire Hubert Curien (IPHC), 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
History, Materials science, Spectrometer, 010308 nuclear & particles physics, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Computer Science Applications, Education, 0103 physical sciences, Ball (bearing), Physics::Accelerator Physics, Física nuclear, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy
Abstract

The reaction of a pulsed 18O beam on a self-supporting and gold-backed isotopically-enriched 164Dy target of thickness 6.3 mg/cm2 at separate primary beam energies of 71, 76 and 80 MeV was studied at the accelerator at the ALTO facility of the IPN Orsay. The γ rays produced were detected using the newly-constructed ν-Ball spectrometer which comprised of HPGe and LaBr3(Ce) detectors. This conference paper describes the methodology and effectiveness of multiplicity/sum-energy gating, for channel selection between fusion evaporation events and lower multiplicity/energy events from inelastic nuclear scattering and Coulomb excitation of the target, and from two-neutron transfer reactions to 166Dy.

Published
2020

23. Contrasting properties of particle-particle and hole-hole excitations in 206Tl and 210Bi nuclei

Author

F. C. L. Crespi, S. Leoni, A. Gargano, Aurelien Blanc, C. Michelagnoli, E. Ruiz-Martinez, Ulli Köster, N. Cieplicka-Oryńczak, S. Bottoni, Ł. W. Iskra, Paolo Mutti, G. Benzoni, Michael Jentschel, V. Werner, B. Fornal, Norbert Pietralla, Institut Laue-Langevin (ILL), and ILL

Subjects
Nuclear and High Energy Physics, Work (thermodynamics), Deduced levels and Jπ 206 Tl, Deduced levels and [formula omitted]206Tl, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Thermal neutron capture, 210Bi, 01 natural sciences, 7. Clean energy, Comparison with shell-model calculations, Nuclear physics, Matrix (mathematics), Atomic orbital, γγ-coin. 206Tl, 0103 physical sciences, Diagonal matrix, medicine, Nuclear structure 206 Tl, 010306 general physics, Mixing (physics), Physics, 010308 nuclear & particles physics, 210 Bi, lcsh:QC1-999, medicine.anatomical_structure, γγ -coin. 206 Tl, Nuclear structure 206Tl, Particle, Branching ratios 206Tl, Nucleus, lcsh:Physics, Branching ratios 206 Tl
Abstract

A complete-spectroscopy investigation of low-lying, low-spin states in the one-proton-hole and one-neutron-hole nucleus 206Tl has been performed by using thermal neutron capture and γ-coincidence technique with the FIPPS Ge array at ILL Grenoble. The new experimental results, together with data for the one-proton-particle and one-neutron-particle nucleus 210Bi (taken from a previous study done at ILL in the EXILL campaign), allowed for an extensive comparison with predictions of shell-model calculations performed with realistic interactions. No phenomenological adjustments were introduced in the calculations. In 210Bi, state energies, transition multipolarities and decay branchings agree well with theory for the three well separated multiplets of states which dominate the low-lying excitations. On the contrary, in 206Tl significant discrepancies are observed: in the same energy region, six multiplets were identified, with a significant mixing among them being predicted, as a consequence of the smaller energy separation between the active orbitals. The discrepancies in 206Tl are attributed to the larger uncertainties in the determination of the off-diagonal matrix elements of the realistic shell-model interaction with respect to the calculated diagonal matrix elements, the only ones playing a major role in the case of 210Bi. The work points to the need of more advanced approaches in the construction of the realistic interactions. Keywords: Nuclear structure 206Tl, 210Bi, γγ-coin. 206Tl, Branching ratios 206Tl, Deduced levels and Jπ 206Tl, Comparison with shell-model calculations

Published
2020

24. Two-neutron and core-excited states in Pb210 : Tracing E3 collectivity and evidence for a new β -decaying isomer in Tl210

Author

G. J. Lane, B. A. Brown, S. Zhu, N. Cieplicka-Oryńczak, M. P. Carpenter, R. V. F. Janssens, F. G. Kondev, Calem Hoffman, W. B. Walters, Zs. Podolyák, R. Broda, C. J. Chiara, D. Seweryniak, B. Fornal, J. Wrzesiński, Ł. W. Iskra, and T. Lauritsen

Subjects
Physics, education.field_of_study, 010308 nuclear & particles physics, Yrast, Population, Coulomb barrier, 01 natural sciences, Excited state, 0103 physical sciences, Gammasphere, Neutron, Atomic physics, 010306 general physics, Spin (physics), education, Multiplet
Abstract

Yrast and near-yrast levels up to an I=17ℏ spin value and a 6-MeV excitation energy have been delineated in the “two-neutron” 210Pb nucleus following deep-inelastic reactions involving 208Pb targets and a number of heavy-ion beams at energies ∼25% above the Coulomb barrier. The level scheme was established on the basis of multifold prompt and delayed coincidence relationships measured with the Gammasphere array. In addition to the previously known states, many new levels were identified. For most of the strongly populated states, spin-parity assignments are proposed on the basis of angular distributions. The reinvestigation of the ν(g9/2)2, 8+ isomeric decay results in the firm identification of the low-energy E2 transitions involved in the 8+→6+→4+ cascade, and in a revised 6+ level half-life of 92(10) ns, nearly a factor of 2 longer than previously measured. Among the newly identified states figure spin I=4–10ℏ levels associated with the νg9/2i11/2 multiplet, as well as yrast states involving νg9/2j15/2, νi11/2j15/2, and ν(j15/2)2 neutron couplings. The highest-spin excitations are understood as 1p−1h core excitations and the yrast population is found to be fragmented to the extent that levels of spin higher than I=17ℏ could not be reached. Four E3 transitions are present in the 210Pb yrast decay; three of these involve the g9/2→j15/2 octupole component, as reflected in the 21(2) and >10 Weisskopf unit enhancements of the B(E3) rates of the first two. The fourth, 16+→13−E3 transition corresponds to the 3− core octupole excitation built on the νi11/2j15/2 state, in analogy to a similar E3 coupling to the νj15/2 level in 209Pb. Shell-model calculations performed for two-neutron states and 1p−1h 208Pb core excitations are in good agreement with the data. Evidence was found for the existence of a hitherto unknown high-spin β-decaying isomer in 210Tl. Shell-model calculations of the 210Tl levels suggest the possibility of a 11+ long-lived, β-decaying state, and the delayed yields observed in various reactions fit rather well with a 210Tl assignment.

Published
2018

25. Testing of the Brink--Axel Hypothesis with the HECTOR+PARIS+KRATTA Set-up

Author

N. Cieplicka-Oryńczak, M. Krzysiek, S. Brambilla, M. Ciemala, P. Bednarczyk, A. Maj, A. Bracco, P. J. Napiorkowski, J. Łukasik, J. Isaak, Izabela Ciepał, B. Fornal, P. Lasko, L. Qi, M. Stanoiu, Y. Sobolev, M. Lewitowicz, S. Bottoni, M. Matejska-Minda, Ch. Schmitt, Piotr Pawłowski, B. Wasilewska, Mohsen Harakeh, K. Guguła, Wiktor Parol, Ł. W. Iskra, F. C. L. Crespi, M. Zieblinski, S. Kihel, J. Grebosz, Atsushi Tamii, M. Kmiecik, A. Szperłak, B. Sowicki, K. Mazurek, Attila Krasznahorkay, 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), 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), 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 de Strasbourg (UNISTRA)-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)-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), and 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)

Subjects
Physics, Set (abstract data type), [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], 010308 nuclear & particles physics, 0103 physical sciences, General Physics and Astronomy, Art history, Physics::Accelerator Physics, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 010306 general physics, 01 natural sciences
Abstract

International audience; A very first experiment in the field of nuclear structure at the Cyclotron Centre Bronowice (CCB) facility in Kraków, Poland has been performed recently. The medical cyclotron IBA Proteus C-235 located at CCB produces proton beams in the energy range of 70–230 MeV, that can be used for experimental purposes as well. In the reported measurement, the energy of scattered protons at the incident beam energy of 85 MeV and emitted γ rays from the excited 208Pb target were measured in coincidence. During the experiment excitations in the energy region of the Giant Quadrupole and Dipole Resonances, as well as the Pygmy Dipole States were observed. By applying different conditions on the data, spectra corresponding to γ decays of excited states to selected low-lying levels in 208Pb were obtained, allowing a look into the Brink–Axel hypothesis.

Published
2018

26. Towards the lowest-energy limit for light ions identification with silicon pixel-type detectors

Author

S. Brambilla, F. C. L. Crespi, B. Fornal, S. Capra, G. Bocchi, C. Boiano, G. Jaworski, N. Cieplicka-Oryńczak, M. Siciliano, M. Ciemala, K. Hadynska-Klek, J. J. Valiente-Dobón, D. Mengoni, D. Bazzacco, Ł. W. Iskra, P. R. John, J.A. Dueñas, G. Benzoni, Alain Goasduff, S. Leoni, F. Recchia, and D. Testov

Subjects
Physics, Nuclear and High Energy Physics, Silicon, 010308 nuclear & particles physics, Detector, chemistry.chemical_element, Alpha particle, Kinetic energy, 01 natural sciences, Particle identification, Ion, Nuclear physics, chemistry, 0103 physical sciences, Nuclear fusion, Nuclear Experiment, 010306 general physics, Nucleon
Abstract

An in-beam test of two pixel-type silicon detectors of the TRACE detector project has been performed at Laboratori Nazionali di Legnaro (Italy). The aim was to investigate the lowest kinetic energy values at which isotopic identification of heavy-ion reactions products with mass $ A\sim 10$ is possible, by using a single-layer silicon detector. Two separate read-out chains, analog and digital, were used, and the Pulse Shape Analysis technique was employed to obtain the particle identification matrices for the digitally processed data. The results confirmed the high capability of the Pulse Shape Analysis method which can be used for light ion identification, with performances similar to the analog approach. Separation in both charge and mass was obtained for Li and Be isotopes, however, the presence of a significant background from alpha particles severely limited the data analysis in the lower energy region. Due to this effect, the identification of the light products (7, 6Li isotopes) could be possible down to $ \sim 24.5$ MeV only, while the 9, 7Be isotopes were separable down to $ \sim 29$ MeV. This gives the value of $ < 4$ MeV/nucleon as the lowest kinetic energy for light products identification by using the pixel-type detectors of the TRACE project, in the present experimental conditions.

Published
2018

27. Neutron-rich nuclei produced at zero degrees in damped collisions induced by a beam of 18O on a 238U target

Author

A. Maj, C. Portail, F. Rotaru, B. Fornal, M. A. Naumenko, L. Olivier, F. de Oliveira Santos, S. Franchoo, A. Chbihi, P. Bednarczyk, A. V. Karpov, C. Petrone, Bertrand Jacquot, Oleg B. Tarasov, Ł. W. Iskra, Yu. E. Penionzhkevich, F. Azaiez, T. Lauritsen, D. Verney, M. Stanoiu, B. Szpak, F. C. L. Crespi, M. Maccormick, O. Sorlin, O. Kamalou, H. Savajols, I. Stefan, R. V. F. Janssens, I. Matea, N. Cieplicka-Oryńczak, M. Ciemala, Dieter Ackermann, Y. Blumenfeld, S. Leoni, Paola Marini, S. Calinescu, F. Hammache, M. Lewitowicz, S. M. Lukyanov, J. C. Thomas, 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), 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), 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), 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and 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)

Subjects
Physics, Nuclear reaction, Nuclear and High Energy Physics, Proton, 010308 nuclear & particles physics, Scattering, Projectile, Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, lcsh:QC1-999, Momentum, Nuclear physics, Cross section (physics), Deep-inelastic collisions, 0103 physical sciences, Neutron, Nuclear reactions, 010306 general physics, Nuclear Experiment, Beam (structure), lcsh:Physics, Exotic nuclei
Abstract

Cross sections and corresponding momentum distributions have been measured for the first time at zero degrees for the exotic nuclei obtained from a beam of 18O at 8.5 MeV/A impinging on a 1 mg/cm2 238U target. Sizable cross sections were found for the production of exotic species arising from the neutron transfer and proton removal from the projectile. Comparisons of experimental results with calculations based on deep-inelastic reaction models, taking into account the particle evaporation process, indicate that zero degree is a scattering angle at which the differential reaction cross section for production of exotic nuclei is at its maximum. This result is important in view of the new generation of zero degrees spectrometers under construction, such as the S3 separator at GANIL, for example. Keywords: Nuclear reactions, Deep-inelastic collisions, Exotic nuclei

Published
2018
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28. Shape coexistence in the odd-odd nucleus Y98 : The role of the g9/2 neutron extruder

Author

W. Urban, M. Czerwiński, J. Kurpeta, T. Rząca-Urban, J. Wiśniewski, T. Materna, Ł. W. Iskra, A. G. Smith, I. Ahmad, A. Blanc, H. Faust, U. Köster, M. Jentschel, P. Mutti, T. Soldner, G. S. Simpson, J. A. Pinston, G. de France, C. A. Ur, V.-V. Elomaa, T. Eronen, J. Hakala, A. Jokinen, A. Kankainen, I. D. Moore, J. Rissanen, A. Saastamoinen, J. Szerypo, C. Weber, and J. Äystö

Subjects
Physics, Large deformation, 010308 nuclear & particles physics, 01 natural sciences, Nuclear physics, Excited state, 0103 physical sciences, Neutron, Gammasphere, Atomic physics, 010306 general physics, Spin (physics), Spectroscopy, Energy (signal processing), Spontaneous fission
Abstract

Excited states in $^{98}\mathrm{Y}$, populated in neutron-induced fission of $^{235}\mathrm{U}$ and in spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, have been studied by means of $\ensuremath{\gamma}$ spectroscopy using the Lohengrin fission-fragment separator at ILL Grenoble and the EXILL, Eurogam2, and Gammasphere Ge arrays. Two new isomers have been found in $^{98}\mathrm{Y}$: a deformed one with ${T}_{1/2}=180(7)$ ns and a rotational band on top of it, and a spherical one with ${T}_{1/2}=0.45(15)\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\text{s}$, analogous to the ${8}^{+}$ isomer in $^{96}\mathrm{Y}$, corresponding to the ${(\ensuremath{\nu}{g}_{7/2},\ensuremath{\pi}{g}_{9/2})}_{{8}^{+}}$ spherical configuration. Using the JYFLTRAP Penning trap, an accurate excitation energy of 465.7(7) keV has been determined for the 2.36-s isomer in $^{98}\mathrm{Y}$. This result and the studies of excited levels in $^{98}\mathrm{Zr}$, populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of the isomer, indicate a new spin-parity, ${I}^{\ensuremath{\pi}}={(7)}^{+}$ for the isomer. The high spin and the decay properties of this isomer suggest the presence of the $9/{2}^{+}[404]$ neutron extruder orbital in its structure. This is consistent with the large deformation of the isomer, reported recently. The present work does not provide arguments to support the special role of the $\ensuremath{\nu}{g}_{7/2}\phantom{\rule{0.16em}{0ex}}\text{\ensuremath{-}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}{g}_{9/2}$ interaction (the spin-orbit-partner, or SOP, mechanism).

Published
2017

29. The Low-spin Structure of $^{206}$Tl Studied by $\gamma $-ray Spectroscopy from Thermal Neutron Capture Reaction

Author

B. Fornal, Ł. W. Iskra, V. Werner, N. Cieplicka-Oryńczak, E. Ruiz-Martinez, Norbert Pietralla, Aurelien Blanc, P. Mutti, C. Michelagnoli, Michael Jentschel, F. C. L. Crespi, Ulli Köster, S. Bottoni, G. Benzoni, S. Leoni, Institut Laue-Langevin (ILL), and ILL

Subjects
Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Thermal neutron capture, General Physics and Astronomy, Spin structure, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, 0103 physical sciences, Gamma spectroscopy, Atomic physics, 010306 general physics, Nuclear Experiment
Abstract

International audience; The low-spin structure of the 206Tl nucleus has been investigated with the FIPPS prompt γ-ray spectrometer of ILL making use of the 205Tl(n,γ)206Tl reaction and the γ-coincidence technique. A large number of excitations up to the neutron binding energy (at 6.5 MeV) in 206Tl were observed. Preliminary results of the data analysis provided the information on the decay scheme of the capture state in 206Tl and on the multipolarities of a number of γ rays. The comparison of the experimental data with shell-model calculations will help describing the proton–hole and neutron–hole couplings near the doubly magic core 208Pb, benchmarking single-particle levels and two-body matrix elements of the residual interaction in this important region of the nuclear chart.

Published
2017

30. Doubly magic Pb208 : High-spin states, isomers, and E3 collectivity in the yrast decay

Author

C. M. Shand, S. Zhu, W. Królas, M. P. Carpenter, W. B. Walters, F. G. Kondev, Calem Hoffman, B. A. Brown, R. V. F. Janssens, N. Cieplicka-Oryńczak, C. J. Chiara, Zs. Podolyák, R. Broda, D. Seweryniak, B. Fornal, J. Wrzesiński, Ł. W. Iskra, T. Lauritsen, and B. Szpak

Subjects
Physics, Angular momentum, Spin states, 010308 nuclear & particles physics, Yrast, Nuclear Theory, Magic (programming), Nuclear shell model, 01 natural sciences, Nuclear physics, Excited state, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics
Abstract

The nucleus ${}^{208}$Pb provides an iconic test of the nuclear shell model because its 82 protons and 126 neutrons are both magic numbers. When excited levels are discovered and characterized, this nucleus provides a means to investigate the mechanisms responsible for the generation of angular momentum and, ultimately, for the development of collectivity. This experiment is a tour de force that reveals extensive new information on ${}^{208}$Pb about high-angular-momentum states, isomeric states, and collective states of octupole nature; thus it serves as a showcase for shell-model descriptions. Many of the states explored show good overall agreement with theory, but others at the highest energies reveal discrepancies, pointing to the need for improved calculations. Above the highest-lying ${28}^{-}$ isomer $\ensuremath{\gamma}$ transitions arising from yet higher spin levels could be identified in two separate experiments as displayed in the figure.

Published
2017

31. Multifaceted Quadruplet of Low-Lying Spin-Zero States in Ni66 : Emergence of Shape Isomerism in Light Nuclei

Author

A. Negreţ, C. Mihai, N. Florea, S. Leoni, S. Pascu, A. Mitu, Yusuke Tsunoda, L. Stroe, C. R. Niţă, S. Calinescu, I. Stiru, Ł. W. Iskra, C. Petrone, G Porzio, P. Petkov, B. Fornal, Rares Suvaila, Alin Titus Serban, N. Cieplicka-Oryǹczak, A. Olacel, Takaharu Otsuka, A. Turturica, G. Bocchi, S. Aydin, L. Stan, M. Boromiza, T. Glodariu, S. Ujeniuc, C. Sotty, A. Ionescu, Michele Sferrazza, R.E. Mihai, N. Marginean, C. A. Ur, M. Krzysiek, D. Bucurescu, F. C. L. Crespi, A. Bracco, S. Toma, C. Costache, A. Oprea, D. Ghiţă, and R. Marginean

Subjects
Physics, Light nucleus, 010308 nuclear & particles physics, SHELL model, Zero (complex analysis), General Physics and Astronomy, State (functional analysis), Prolate spheroid, 01 natural sciences, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics, Spin (physics), Energy (signal processing)
Abstract

A search for shape isomers in the ^{66}Ni nucleus was performed, following old suggestions of various mean-field models and recent ones, based on state-of-the-art Monte Carlo shell model (MCSM), all considering ^{66}Ni as the lightest nuclear system with shape isomerism. By employing the two-neutron transfer reaction induced by an ^{18}O beam on a ^{64}Ni target, at the sub-Coulomb barrier energy of 39 MeV, all three lowest-excited 0^{+} states in ^{66}Ni were populated and their γ decay was observed by γ-coincidence technique. The 0^{+} states lifetimes were assessed with the plunger method, yielding for the 0_{2}^{+}, 0_{3}^{+}, and 0_{4}^{+} decay to the 2_{1}^{+} state the B(E2) values of 4.3, 0.1, and 0.2 Weisskopf units (W.u.), respectively. MCSM calculations correctly predict the existence of all three excited 0^{+} states, pointing to the oblate, spherical, and prolate nature of the consecutive excitations. In addition, they account for the hindrance of the E2 decay from the prolate 0_{4}^{+} to the spherical 2_{1}^{+} state, although overestimating its value. This result makes ^{66}Ni a unique nuclear system, apart from ^{236,238}U, in which a retarded γ transition from a 0^{+} deformed state to a spherical configuration is observed, resembling a shape-isomerlike behavior.

Published
2017

32. The first results from studies of gamma decay of proton-induced excitations at the ccb facility

Author

A. Szperłak, B. Wasilewska, M. Kmiecik, Izabela Ciepał, K. Mazurek, Piotr Pawłowski, J. Łukasik, Wiktor Parol, F. C. L. Crespi, B. Fornal, M. Zieblinski, Atsushi Tamii, J. Grebosz, B. Sowicki, A. Maj, M. Matejska-Minda, K. Guguła, P. J. Napiorkowski, S. Brambilla, Ł. W. Iskra, M. Krzysiek, M. Ciemala, P. Lasko, A. Bracco, and A. Giaz

Subjects
Physics, Nuclear physics, Physics and Astronomy (all), Proton, Gamma ray, General Physics and Astronomy
Published
2017

33. New isomer in $^{96}$Y marking the onset of deformation at N = 57

Author

T. Kröll, Zs. Podolyák, C. A. Ur, Michael Jentschel, S. Bottoni, W. Korten, D. Mengoni, D. Bazzacco, F. C. L. Crespi, B. Melon, Torsten Soldner, Ulli Köster, C. Porzio, S. Lalkovski, N. Marginean, Aurelien Blanc, G. Benzoni, G. Bocchi, N. Cieplicka-Oryńczak, P. H. Regan, P. Mutti, B. Fornal, L. M. Fraile, B. Szpak, S. Leoni, Alison Bruce, J.-M. Régis, D. R. Napoli, C. Michelagnoli, A. Nannini, G. S. Simpson, Ł. W. Iskra, W. Urban, A. Petrovici, B. Million, Institut Laue-Langevin (ILL), ILL, Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, 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, Shape change, 010308 nuclear & particles physics, General Physics and Astronomy, chemistry.chemical_element, Yttrium, Deformation (meteorology), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Molecular physics, Nuclear magnetic resonance, chemistry, Cascade, Excited state, 0103 physical sciences, 010306 general physics, Excitation
Abstract

EXILL experimental campaign; International audience; The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6−. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4− isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model.

Published
2017

34. Medium and high spin structure in the $^{94}$Y isotope produced in fission induced by cold neutrons

Author

Ł W Iskra, B Fornal, S Leoni, G Bocchi, A Blanc, S Bottoni, N Cieplicka-Oryńczak, M Jentschel, U Köster, C Michelagnoli, P Mutti, T Soldner, G de France, G S Simpson, C A Ur, W Urban, Institut Laue-Langevin (ILL), ILL, 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), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), 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), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)

Subjects
Physics, Cold fission, Cluster decay, Isotope, 010308 nuclear & particles physics, Fission, Neutron emission, Astrophysics::High Energy Astrophysical Phenomena, Fission product yield, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Condensed Matter Physics, 7. Clean energy, 01 natural sciences, Fast fission, Atomic and Molecular Physics, and Optics, Nuclear physics, 0103 physical sciences, Neutron, 010306 general physics, Mathematical Physics
Abstract

International audience; The level scheme of the neutron-rich 94Y isotope has been extended up to the 5324 keV excitation energy. During the analysis, a structure above the previously known (5+) isomer, at 1202 keV, was extended by employing multifold gamma-ray coincidence relationships measured with the EXILL array. For some of the new states, the spin-parity assignment has been proposed on the basis of gamma angular correlations and shell-model considerations. The newly identified structure is characteristic of spherical or nearly spherical configurations and no evidence for new isomers and rotational patterns was found.

Published
2017

35. Investigating Core Excitations in the $^{131}$Sn One-valence-hole Nucleus

Author

Michael Jentschel, S. Leoni, C. Michelagnoli, S. Bottoni, A. Bracco, G. Benzoni, Ulli Köster, B. Fornal, Aurelien Blanc, P. Mutti, D. Bazzacco, F. C. L. Crespi, Gianluca Colò, C. A. Ur, G. Bocchi, L. Gatti, N. Cieplicka-Oryńczak, B. Million, Torsten Soldner, W. Urban, Ł. W. Iskra, Institut Laue-Langevin (ILL), and ILL

Subjects
Physics, Valence (chemistry), [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Molecular physics, medicine.anatomical_structure, 0103 physical sciences, medicine, Nuclear Experiment, 010306 general physics, Nucleus
Abstract

International audience; The structure of the 131Sn nucleus was studied at the Institut LaueLangevin by prompt-delayed γ-ray spectroscopy across the 0.3 µs, 23/2− isomeric state at 4670 keV, following cold-neutron-induced fission of 235U and 241Pu targets. New γ-ray transitions are observed and the results are compared with theoretical calculations performed with the Hybrid Configuration Mixing Model. The latter suggests that the majority of the states can be well-described in terms of couplings between single-hole degrees of freedom and 132Sn core excitations, pointing to a robust neutron shell closure at N = 82.

Published
2019

36. Shell-model states with seniorityν=3, 5, and 7 in odd-Aneutron-rich Sn isotopes

Author

R. V. F. Janssens, B. Fornal, J. Wrzesiński, T. Lauritsen, N. Hoteling, S. Zhu, M. P. Carpenter, W. Królas, D. Seweryniak, C. J. Chiara, F. G. Kondev, R. Broda, T. Pawłat, I. Stefanescu, Ł. W. Iskra, and W. B. Walters

Subjects
Physics, education.field_of_study, 010308 nuclear & particles physics, Population, Gamma ray, State (functional analysis), 01 natural sciences, Excited state, 0103 physical sciences, Gammasphere, Neutron, Atomic physics, 010306 general physics, education, Excitation, Spin-½
Abstract

Excited states with seniority $\ensuremath{\nu}=3$, 5, and 7 have been investigated in odd neutron-rich $^{119,121,123,125}\text{Sn}$ isotopes produced by fusion-fission of 6.9-MeV/$A\phantom{\rule{4pt}{0ex}}^{48}\text{Ca}$ beams with $^{208}\text{Pb}$ and $^{238}\text{U}$ targets and by fission of a $^{238}\text{U}$ target bombarded with 6.7-MeV/$A\phantom{\rule{4pt}{0ex}}^{64}\text{Ni}$ beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known $27/{2}^{\ensuremath{-}}$ isomers were expanded by identifying new deexcitation paths feeding $23/{2}^{+}$ long-lived states and $21/{2}^{+}$ levels. Competing branches in the decay of $23/{2}^{\ensuremath{-}}$ states toward two $19/{2}^{\ensuremath{-}}$ levels were delineated as well. In $^{119}\text{Sn}$, a new $23/{2}^{+}$ isomer was identified, while a similar $23/{2}^{+}$ long-lived state, proposed earlier in $^{121}\text{Sn}$, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of $\ensuremath{\nu}=3$ excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the $27/{2}^{\ensuremath{-}}$ isomers, an elaborate structure of negative-parity levels was established reaching the ($39/{2}^{\ensuremath{-}}$), $\ensuremath{\nu}=7$ states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity ($35/{2}^{+}$), ($31/{2}^{+}$), and ($27/{2}^{+}$) states were established, feeding the $23/{2}^{+}$ isomers via cascades of three transitions. In the $^{121,123}\text{Sn}$ isotopes, these sequences also enabled the delineation of higher-lying levels, up to ($43/{2}^{+}$) states. In $^{123}\text{Sn}$, a short half-life was determined for the ($35/{2}^{+}$) state. Shell-model calculations were carried out for all the odd Sn isotopes, from $^{129}\text{Sn}$ down to $^{119}\text{Sn}$, and the results were found to reproduce the experimental level energies rather well. Nevertheless, some systematic deviations between calculated and experimental energies, especially for positive-parity states, point to the need to improve some of the two-body interactions used in calculations. The computed wave-function amplitudes provide for a fairly transparent interpretation of the observed level structures. The systematics of level energies over the broad $A$ = 117--129 range of Sn isotopes displays a smooth decrease with mass $A$, and the observed regularity confirms most of the proposed spin-parity assignments. The systematics of the $B(E2)$ reduced transition probabilities extracted for the $23/{2}^{+}$ and $19/{2}^{+}$ isomers is discussed with an emphasis on the close similarity of the observed $A$ dependence with that of the $E2$ transition rates established for other $\ensuremath{\nu}=2$, 3, and 4 isomers in the Sn isotopic chain.

Published
2016

37. Higher-seniority excitations in even neutron-rich Sn isotopes

Author

S. Zhu, R. V. F. Janssens, N. Hoteling, D. Seweryniak, R. Broda, C. J. Chiara, W. Królas, B. Szpak, Ł. W. Iskra, T. Lauritsen, W. B. Walters, F. G. Kondev, B. Fornal, I. Stefanescu, M. P. Carpenter, J. Wrzesiński, and T. Pawłat

Subjects
Physics, Nuclear and High Energy Physics, education.field_of_study, Excited state, Yrast, Population, Gammasphere, Neutron, Sensitivity (control systems), Atomic physics, education, Wave function, Excitation
Abstract

Excited states above the seniority $\ensuremath{\nu}=2$ isomers have been investigated in even neutron-rich ${}^{118--128}$Sn isotopes produced by fusion-fission of 6.9 MeV/$A$ $^{48}\mathrm{Ca}$ beams with $^{208}\mathrm{Pb}$ and $^{238}\mathrm{U}$ targets and by fission of 6.7 MeV/$A$ $^{64}\mathrm{Ni}$ beams on a $^{238}\mathrm{U}$ target. Level schemes up to excitation energies in excess of 8 MeV have been established based on multifold $\ensuremath{\gamma}$-ray coincidence relationships measured with the Gammasphere array. Isotopic identification of crucial transitions was achieved through a number of techniques, including prompt and delayed cross-coincidence methods. As a result, seniority $\ensuremath{\nu}=4$, 15${}^{\ensuremath{-}}$, and 13${}^{\ensuremath{-}}$ isomers were observed and their half-lives determined. These long-lived states in turn served as steppingstones to delineate the isomeric decays and to locate higher-lying states with good sensitivity. As the observed isomeric decays feed down to 10${}^{+}$ and 7${}^{\ensuremath{-}}$ isomers, firm spin-parity assignments could be proposed for most of the seniority $\ensuremath{\nu}=4$ states. Higher-lying, seniority $\ensuremath{\nu}=6$ levels were assigned tentatively on the basis of the observed deexcitation paths as well as of general yrast population arguments. Shell-model calculations were carried out down to $^{122}\mathrm{Sn}$ in the ${g}_{7/2}$, ${d}_{5/2}$, ${d}_{3/2}$, ${s}_{1/2}$, and ${h}_{11/2}$ model space of neutron holes with respect to a $^{132}\mathrm{Sn}$ core. Effective two-body interactions were adjusted such that satisfactory agreement with data was achieved for $^{130}\mathrm{Sn}$. The results reproduce the experimental level energies and spin-parity assignments rather well. The intrinsic structure of the states is discussed on the basis of the calculated wave functions which, in many instances, point to complex configurations. In a few cases, the proposed assignments lead to unresolved issues. The smooth, systematic decrease of the level energies with mass $A$ is accompanied by the similarly regular behavior with $A$ of the reduced transition probabilities extracted from the isomeric half-lives. This $A$ dependence is discussed for the $E1$ and $E2$ transitions in the decay of the seniority $\ensuremath{\nu}=4$ isomers and is compared to that determined in earlier work for the $E2$ transition rates from the $\ensuremath{\nu}=2,3$ isomers.

Published
2014

38. Spectroscopic study of the64,66,68Ni isotopes populated in64Ni + 238U collisions

Author

Ł. W. Iskra, W. Krolas, R. Broda, R. V. F. Janssens, T. Lauritsen, C. J. Chiara, N. Hoteling, I. Stefanescu, B. Fornal, D. Seweryniak, W. B. Walters, X. Wang, T. Pawłat, F. G. Kondev, S. Zhu, J. Wrzesinski, and M. P. Carpenter

Subjects
Physics, Nuclear and High Energy Physics, education.field_of_study, Proton, Excited state, Population, Gammasphere, Neutron, Atomic physics, education, Space (mathematics), Excitation, Spin-½
Abstract

Excited states in ${}^{64}$Ni, ${}^{66}$Ni, and ${}^{68}$Ni were populated in quasielastic and deep-inelastic reactions of a 430-MeV ${}^{64}$Ni beam on a thick ${}^{238}$U target. Level schemes including many nonyrast states were established up to respective excitation energies of 6.8, 8.2, and 7.8 MeV on the basis of \ensuremath{\gamma}-ray coincidence events measured with the Gammasphere array. Spin-parity assignments were deduced from an angular-correlation analysis and from observed \ensuremath{\gamma}-decay patterns, but information from earlier \ensuremath{\gamma}-spectroscopy and nuclear-reaction studies was used as well. The spin assignments for nonyrast states were supported further by their observed population pattern in quasielastic reactions selected through a cross-coincidence technique. Previously established isomeric-state decays in ${}^{66}$Ni and ${}^{68}$Ni were verified and delineated more extensively through a delayed-coincidence analysis. A number of new states located above these long-lived states were identified. Shell-model calculations were carried out in the ${p}_{3/2}{f}_{5/2}{p}_{1/2}{g}_{9/2}$ model space with two effective interactions using a ${}^{56}$Ni core. Satisfactory agreement between experimental and computed level energies was achieved, even though the calculations indicate that all the states are associated with rather complex configurations. This complexity is illustrated through the discussion of the structure of the negative-parity states and of the M1 decays between them. The best agreement between data and calculations was achieved for ${}^{68}$Ni, the nucleus where the calculated states have the simplest structure. In this nucleus, the existence of two low-spin states reported recently was confirmed as well. Results of the present study do not indicate any involvement of collective degrees of freedom and confirm the validity of a shell-model description in terms of neutron excitations combined with a closed $Z$ $=$ 28 proton shell. Further improvements to the calculations are desirable.

Published
2012

39. High-spin shell model states in neutron-rich Sn isotopes

Author

B. Fornal, R. Broda, S. Zhu, I. Stefanescu, B. Szpak, Ł. W. Iskra, T. Pawłat, D. Seweryniak, W. B. Walters, T. Lauritsen, R. V. F. Janssens, M. P. Carpenter, W. Królas, C. J. Chiara, N. Hoteling, F. G. Kondev, and J. Wrzesiński

Subjects
Nuclear reaction, Mass number, History, Isotope, Fission, Chemistry, Nuclear Theory, Computer Science Applications, Education, Isotopes of tin, Neutron, Atomic physics, Nuclear Experiment, Nucleon, Spin (physics)
Abstract

High-spin states with the seniority v ≥ 2 have been investigated in the neutron-rich 118,120,122,124,126Sn isotopes. They were produced in fusion-fission processes following 48Ca + 208Pb, 48Ca + 238U reactions and via fission of target nuclei in the 64Ni + 238U system. By employing techniques of delayed- and cross-coincidences, it was possible to establish level schemes up to an 8 MeV excitation energy. The 13− and 15− states were identified as being isomeric and their half-lives were determined. The reduced transition probabilities extracted for isomeric transitions behave very regularly with the mass number A. The spin-parity values assigned to or suggested for the identified states were supported by shell-model calculations and by systematics.

Published
2015

40. E2 Transition Probabilities for Decays of Isomers Observed in Neutron-rich Odd Sn Isotopes

Author

S. Zhu, J. Wrzesinski, M. P. Carpenter, T. Pawłat, W. Krolas, T. Lauritsen, W. B. Walters, C. J. Chiara, D. Seweryniak, B. Fornal, F. G. Kondev, R. Broda, R. V. F. Janssens, I. Stefanescu, N. Hoteling, and Ł. W. Iskra

Subjects
Physics, Nuclear physics, Amplitude, Isotope, Fission, General Physics and Astronomy, Neutron, Atomic physics, Coincidence
Abstract

High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudes for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.

Published
2015

43. New isomer in 96Y marking the onset of deformation at N = 57.

Author

Ł. W. Iskra, B. Fornal, S. Leoni, G. Bocchi, A. Petrovici, C. Porzio, A. Blanc, G. De France, M. Jentschel, U. Köster, P. Mutti, J.-M. Régis, G. Simpson, T. Soldner, C. A. Ur, W. Urban, D. Bazzacco, G. Benzoni, S. Bottoni, and A. Bruce

Abstract

The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6−. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4− isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model. [ABSTRACT FROM AUTHOR]

Published
2017
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