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7 results on '"C. Andreoiu"'

1. Use of Bayesian Optimization to Understand the Structure of Nuclei

Author

J. Hooker, J. Kovoor, K.L. Jones, R. Kanungo, M. Alcorta, J. Allen, C. Andreoiu, L. Atar, D.W. Bardayan, S.S. Bhattacharjee, D. Blankstein, C. Burbadge, S. Burcher, W.N. Catford, S. Cha, K. Chae, D. Connolly, B. Davids, N. Esker, F.H. Garcia, S. Gillespie, R. Ghimire, A. Gula, G. Hackman, S. Hallam, M. Hellmich, J. Henderson, M. Holl, P. Jassal, S. King, T. Knight, R. Kruecken, A. Lepailleur, J. Liang, L. Morrison, P.D. O’Malley, S.D. Pain, X. Pereira-Lopez, A. Psaltis, A. Radich, A.C. Shotter, M. Vostinar, M. Williams, and O. Workman

Subjects
Nuclear and High Energy Physics, Direct reaction, FOS: Physical sciences, Transfer reaction, 01 natural sciences, Atomic, Stable ion beam, Particle and Plasma Physics, Affordable and Clean Energy, 0103 physical sciences, Nuclear, Nuclear Experiment (nucl-ex), 010306 general physics, Instrumentation, Nuclear Experiment, Bayesian optimization, Applied Physics, 010308 nuclear & particles physics, Low-energy reactions, Geant4 simulation, Molecular, Computational Physics (physics.comp-ph), Geochemistry, Interdisciplinary Engineering, Radioactive ion beam, Physics - Computational Physics
Abstract

Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a $^{12}$Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the $^{12}$C(d,p) reaction to well-known states in $^{13}$C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for $^{13}$Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in $^{13}$C were extracted to better than 90 keV, paving a way for extracting information on $^{13}$Be., 8 pages, 6 figures

Published
2021

2. Signature splitting of the g7/2[404]7/2+ bands in Ba131 and Ce133

Author

B. Ding, C. M. Petrache, S. Guo, E. A. Lawrie, I. Wakudyanaye, Z. H. Zhang, H. L. Wang, H. Y. Meng, D. Mengoni, Y. H. Qiang, J. G. Wang, C. Andreoiu, A. Astier, A. Avaa, T. Bäck, R. A. Bark, D. Bazzacco, A. Boso, T. D. Bucher, B. Cederwall, M. V. Chisapi, H. L. Fan, F. Galtarossa, F. H. Garcia, A. Goasduff, G. Jaworski, P. Jones, I. Kuti, J. J. Lawrie, G. S. Li, R. Li, M. L. Liu, Z. Liu, B. Lomberg, B. F. Lv, T. Marchlewski, L. Mdletshe, L. Msebi, S. H. Mthembu, D. R. Napoli, A. Netshiya, M. F. Nkalanga, J. N. Orce, K. Ortner, F. Recchia, S. Riccetto, A. Rohilla, T. W. Seakamela, M. Siciliano, M. A. Sithole, D. Sohler, J. Srebrny, D. Testov, A. Tucholski, J. J. Valiente-Dobón, F. Wentzel, K. Whitmore, Y. H. Zhang, K. K. Zheng, X. H. Zhou, and B. R. Zikhali

Subjects
010308 nuclear & particles physics, 0103 physical sciences, 010306 general physics, 01 natural sciences
Published
2021
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3. Excitations of the magic N=50 neutron-core revealed in Ga81

Author

J. Dudouet, A. Lemasson, G. Maquart, F. Nowacki, D. Verney, M. Rejmund, G. Duchêne, O. Stezowski, E. Clément, C. Michelagnoli, A. Korichi, C. Andreoiu, A. Astier, G. de Angelis, G. de France, C. Delafosse, I. Deloncle, F. Didierjean, Z. Dombradi, C. Ducoin, A. Gadea, A. Gottardo, D. Guinet, B. Jacquot, P. Jones, T. Konstantinopoulos, I. Kuti, F. Le Blanc, S. M. Lenzi, G. Li, R. Lozeva, B. Million, D. R. Napoli, A. Navin, R. M. Pérez-Vidal, C. M. Petrache, D. Ralet, M. Ramdhane, N. Redon, C. Schmitt, and D. Sohler

Subjects
Physics, Valence (chemistry), 010308 nuclear & particles physics, Fission, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, 01 natural sciences, Ion, 0103 physical sciences, Physics::Atomic and Molecular Clusters, AGATA, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Spectroscopy, Excitation
Abstract

The high-spin states of the neutron-rich Ga81, with three valence protons outside a Ni78 core, were measured. The measurement involved prompt γ-ray spectroscopy of fission fragments isotopically identified using the combination of the variable mode spectrometer (VAMOS++) and the advanced gamma tracking array (AGATA). The new γ-ray transitions, observed in coincidence with Ga81 ions, and the corresponding level scheme do not confirm the high-spin levels reported earlier. The newly observed high-spin states in Ga81 are interpreted using the results of state-of-the-art large-scale shell model (LSSM) calculations. The lower excitation energy levels are understood as resulting from the recoupling of three valence protons to the closed doubly magic core, while the highest excitation energy levels correspond to excitations of the magic N=50 neutron core. These results support the doubly magic character of Ni78 and the persistence of the N=50 shell closure but also highlight the presence of strong proton-neutron correlations associated with the promotion of neutrons across the magic N=50 shell gap, only few nucleons away from Ni78.

Published
2019
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4. Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni78 Region: A Hint from Lifetime Measurements

Author

C. Delafosse, D. Verney, P. Marević, A. Gottardo, C. Michelagnoli, A. Lemasson, A. Goasduff, J. Ljungvall, E. Clément, A. Korichi, G. De Angelis, C. Andreoiu, M. Babo, A. Boso, F. Didierjean, J. Dudouet, S. Franchoo, A. Gadea, G. Georgiev, F. Ibrahim, B. Jacquot, T. Konstantinopoulos, S. M. Lenzi, G. Maquart, I. Matea, D. Mengoni, D. R. Napoli, T. Nikšić, L. Olivier, R. M. Pérez-Vidal, C. Portail, F. Recchia, N. Redon, M. Siciliano, I. Stefan, O. Stezowski, D. Vretenar, M. Zielinska, D. Barrientos, G. Benzoni, B. Birkenbach, A. J. Boston, H. C. Boston, B. Cederwall, L. Charles, M. Ciemala, J. Collado, D. M. Cullen, P. Désesquelles, G. de France, C. Domingo-Pardo, J. Eberth, V. González, L. J. Harkness-Brennan, H. Hess, D. S. Judson, A. Jungclaus, W. Korten, A. Lefevre, F. Legruel, R. Menegazzo, B. Million, J. Nyberg, B. Quintana, D. Ralet, P. Reiter, F. Saillant, E. Sanchis, Ch. Theisen, and J. J. Valiente Dobon

Subjects
Physics, Valence (chemistry), Proton, 010308 nuclear & particles physics, General Physics and Astronomy, 01 natural sciences, Particle identification, Recoil, Excited state, 0103 physical sciences, Quadrupole, Neutron, AGATA, Atomic physics, 010306 general physics
Abstract

Lifetime measurements of excited states of the light N = 52 isotones 88 Kr , 86 Se , and 84 Ge have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B ( E 2 ; 2 + → 0 + ) and B ( E 2 ; 4 + → 2 + ) were obtained for the first time for the hard-to-reach 84 Ge . While the B ( E 2 ; 2 + → 0 + ) values of 88 Kr , 86 Se saturate the maximum quadrupole collectivity offered by the natural valence ( 3 s , 2 d , 1 g 7 / 2 , 1 h 11 / 2 ) space of an inert 78 Ni core, the value obtained for 84 Ge largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N ≲ 49 , extend beyond N = 50 . The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector ρ field in shell-structure evolution.

Published
2018
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5. Kr369660 –Low- Z Boundary of the Island of Deformation at N=60

Author

J. Dudouet, A. Lemasson, G. Duchêne, M. Rejmund, E. Clément, C. Michelagnoli, F. Didierjean, A. Korichi, G. Maquart, O. Stezowski, C. Lizarazo, R. M. Pérez-Vidal, C. Andreoiu, G. de Angelis, A. Astier, C. Delafosse, I. Deloncle, Z. Dombradi, G. de France, A. Gadea, A. Gottardo, B. Jacquot, P. Jones, T. Konstantinopoulos, I. Kuti, F. Le Blanc, S. M. Lenzi, G. Li, R. Lozeva, B. Million, D. R. Napoli, A. Navin, C. M. Petrache, N. Pietralla, D. Ralet, M. Ramdhane, N. Redon, C. Schmitt, D. Sohler, D. Verney, D. Barrientos, B. Birkenbach, I. Burrows, L. Charles, J. Collado, D. M. Cullen, P. Désesquelles, C. Domingo Pardo, V. González, L. Harkness-Brennan, H. Hess, D. S. Judson, M. Karolak, W. Korten, M. Labiche, J. Ljungvall, R. Menegazzo, D. Mengoni, A. Pullia, F. Recchia, P. Reiter, M. D. Salsac, E. Sanchis, Ch. Theisen, J. J. Valiente-Dobón, and M. Zielińska

Subjects
Physics, Proton, 010308 nuclear & particles physics, Fission, General Physics and Astronomy, 01 natural sciences, Atomic orbital, Excited state, Neutron number, 0103 physical sciences, Quadrupole, Atomic number, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy
Abstract

Prompt γ-ray spectroscopy of the neutron-rich $^{96}$Kr, produced in transfer- and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS++ spectrometer. A second excited state, assigned to $J^π$ = $4^+$, is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R4/2 = E($4^+$)/E($2^+$) = 2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N = 60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z = 36, of similar amplitude to that observed at N = 60 at higher Z values. A possible reason for this abrupt transition could be related to the insufficient proton excitations in the g9/2, d5/2, and s1/2 orbitals to generate strong quadrupole correlations or to the coexistence of competing different shapes. An unexpected continuous decrease of R4/2 as a function of the neutron number up to N = 60 is also evidenced. This measurement establishes the Kr isotopic chain as the low-Z boundary of the island of deformation for N = 60 isotones. A comparison with available theoretical predictions using different beyond mean-field approaches shows that these models fail to reproduce the abrupt transitions at N = 60 and Z = 36.

Published
2017
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6. EXPERIMENTAL MEASUREMENT OF THE DEFORMATION THROUGH THE ELECTROMAGNETIC PROBE: SHAPE COEXISTENCE IN EXOTIC <font>KR</font> AND <font>SR</font> ISOTOPES

Author

E. CLÉMENT, G. DE FRANCE, J.M. CASANDJIAN, A. GÖRGEN, W. KORTEN, E. BOUCHEZ, A. CHATILLON, A. HÜRSTEL, Y. LE COZ, A. OBERTELLI, C. THEISEN, J.N. WILSON, J.-P. DELAROCHE, M. GIROD, H. GOUTTE, S. PÉRU, T. CZOSNYKA, J. IWANICKI, P.J. NAPIORKOWSKI, J. SREBRNY, K. WRZOSEK-LIPSKA, M. ZIELIŃSKA, N. BREE, I. STEFANESCU, J. VAN DE WALLE, C. ANDREOIU, P.A. BUTLER, R.-D. HERZBERG, D.G. JENKINS, G.D. JONES, A. PETTS, F. BECKER, J. GERL, W.N. CATFORD, C.N. TIMIS, G. SLETTEN, G. GEORGIEV, J. LJUNGVALL, 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 Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), 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), 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 Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Nuclear and High Energy Physics, Isotope, 010308 nuclear & particles physics, Nuclear Theory, General Physics and Astronomy, Experimental data, Isotopes of krypton, Coulomb excitation, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Nuclear physics, Excited state, 0103 physical sciences, Quadrupole, Physics::Atomic Physics, Deformation (engineering), Atomic physics, Nuclear Experiment, 010306 general physics, Mixing (physics)
Abstract

The light krypton isotopes were studied in a series of Coulomb excitation experiments using radioactive beams at GANIL. The static quadrupole moments found in these experiments give firm experimental evidence for the shape coexistence scenario that is based on theoretical calculations and on the systematics of low-lying excited 0+ states. The experimental results are interpreted within a phenomenological two-band mixing model. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and compared to experimental data.

Published
2011
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7. Shape coexistence in neutron-deficient krypton isotopes

Author

E. Clément, A. Görgen, W. Korten, E. Bouchez, A. Chatillon, J.-P. Delaroche, M. Girod, H. Goutte, A. Hürstel, Y. Le Coz, A. Obertelli, S. Péru, Ch. Theisen, J. N. Wilson, M. Zielińska, C. Andreoiu, F. Becker, P. A. Butler, J. M. Casandjian, W. N. Catford, T. Czosnyka, G. de France, J. Gerl, R.-D. Herzberg, J. Iwanicki, D. G. Jenkins, G. D. Jones, P. J. Napiorkowski, G. Sletten, C. N. Timis, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Département de Physique Théorique et Appliquée (DPTA), DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Helmholtz zentrum für Schwerionenforschung GmbH (GSI), 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), SPIRAL, and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Physics, Nuclear and High Energy Physics, 21.10.Ky, 21.60.-n, 23.20.Js, 25.70.De, 27.50+e, Isotope, 010308 nuclear & particles physics, Nuclear Theory, Hartree–Fock method, Isotopes of krypton, Coulomb excitation, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Excited state, 0103 physical sciences, Quadrupole, Diagonal matrix, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics
Abstract

GANIL E344aS; Shape coexistence in the light krypton isotopes was studied in two low-energy Coulomb excitation experiments using radioactive $^{74}$Kr and $^{76}$Kr beams from the SPIRAL facility at GANIL. The ground-state bands in both isotopes were populated up to the $8^+$ state via multi-step Coulomb excitation, and several non-yrast states were observed. Large sets of matrix elements were extracted for both nuclei from the observed $\\gamma$-ray yields. Diagonal matrix elements were determined by utilizing the reorientation effect. In both isotopes the spectroscopic quadrupole moments for the ground-state bands and the bands based on excited $0_2^+$ states are found to have opposite signs. The experimental data are interpreted within a phenomenological two-band mixing model and model-independent quadrupole invariants are deduced for the relevant $0^+$ states using the complete sets of matrix elements and the formalism of quadrupole sum rules. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and are compared both with the experimental results and with recent calculations using the Skyrme SLy6 effective interaction and the full generator-coordinate method restricted to axial shapes.

Published
2007
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