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1. Coulomb breakup of neutron-rich $^{29,30}$Na isotopes near the island of inversion

Author

Rahaman, A ., Datta, Ushasi, Aumann, T., Beceiro-Novo, S., Boretzky, K., Caesar, C., Carlson, B. V., Catford, W. N., Chakraborty, S., Chartier, M., Cortina-Gil, D., Angelis, G. De., Gonzalez-Diaz, D., Emling, H., Fernandez, P. Diaz, Fraile, L. M., Ershova, O., Geissel, H., Jonson, B., Johansson, H., Kalantar-Nayestanaki, N., Krücken, R., Kröll, T., Kurcewicz, J., Langer, C., Bleis, T. Le, Leifels, Y., Münzenberg, G., Marganiec, J., Nilsson, T., Nociforo, C., Najafi, A., Panin, V., Paschalis, S., Plag, R., Reifarth, R., Rigollet, C., Ricciardi, V., Rossi, D., Scheit, H., Simon, H., Scheidenberger, C., Typel, S., Taylor, J., Togano, Y., Volkov, V., Weick, H., Wagner, A., Wamers, F., Weigand, M., Winfield, J. S., Yakorev, D., and Zoric, M.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

First results are reported on the ground state configurations of the neutron-rich $^{29,30}$Na isotopes, obtained via Coulomb dissociation (CD) measurements as a method of the direct probe. The invariant mass spectra of those nuclei have been obtained through measurement of the four-momentum of all decay products after Coulomb excitation on a $^{208}Pb$ target at energies of 400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated Coulomb-dissociation cross-sections (CD) of 89 $(7)$ mb and 167 $(13)$ mb up to excitation energy of 10 MeV for one neutron removal from $^{29}$Na and $^{30}$Na respectively, have been extracted. The major part of one neutron removal, CD cross-sections of those nuclei populate core, in its' ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of $^{29}$Na${(3/2^+)}$ and $^{30}$Na${(2^+)}$ is the $d$ orbital with small contribution in the $s$-orbital which are coupled with ground state of the core. The ground state configurations of these nuclei are as $^{28}$Na$_{gs (1^+)\otimes\nu_{s,d}$ and $^{29}$Na$_{gs}(3/2^+)\otimes\nu_{ s,d}$, respectively. The ground state spin and parity of these nuclei, obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the $s$ and $d$ orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with the shell model calculation using MCSM suggests a lower limit of around 4.3 MeV of the sd-pf shell gap in $^{30}$Na., Comment: Modified version of the manuscript is accepted for publication in Journal of Physics G, Jan., 2017

Published
2016
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2. Beyond the Neutron Drip-Line: The Unbound Oxygen Isotopes 25O and 26O

Author

Caesar, C., Simonis, J., Adachi, T., Aksyutina, Y., Alcantara, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Aumann, T., Avdeichikov, V., Barr, M., Beceiro, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boretzky, K., Borge, M. J. G., Burgunder, G., Caamano, M., Casarejos, E., Catford, W., Cederkäll, J., Chakraborty, S., Chartier, M., Chulkov, L., Cortina-Gil, D., Pramanik, U. Datta, Fernandez, P. Diaz, Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L. M., Freer, M., Freudenberger, M., Fynbo, H. O. U., Galaviz, D., Geissel, H., Gernhäuser, R., Golubev, P., Diaz, D. Gonzalez, Hagdahl, J., Heftrich, T., Heil, M., Heine, M., Heinz, A., Henriques, A., Holl, M., Holt, J. D., Ickert, G., Ignatov, A., Jakobsson, B., Johansson, H. T., Jonson, B., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Knöbel, R., Kröll, T., Krücken, R., Kurcewicz, J., Labiche, M., Langer, C., Bleis, T. Le, Lemmon, R., Lepyoshkina, O., Lindberg, S., Machado, J., Marganiec, J., Maroussov, V., Menéndez, J., Mostazo, M., Movsesyan, A., Najafi, A., Nilsson, T., Nociforo, C., Panin, V., Perea, A., Pietri, S., Plag, R., Prochazka, A., Rahaman, A., Rastrepina, G., Reifarth, R., Ribeiro, G., Ricciardi, M. V., Rigollet, C., Riisager, K., Röder, M., Rossi, D. M., del Rio, J. Sanchez, Savran, D., Scheit, H., Schwenk, A., Simon, H., Sorlin, O., Stoica, V., Streicher, B., Taylor, J., Tengblad, O., Terashima, S., Thies, R., Togano, Y., Uberseder, E., Van de Walle, J., Velho, P., Volkov, V., Wagner, A., Wamers, F., Weick, H., Weigand, M., Wheldon, C., Wilson, G., Wimmer, C., Winfield, J. S., Woods, P., Yakorev, D., Zhukov, M. V., Zilges, A., Zoric, M., Zuber, K., and collaboration, R3B

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

The very neutron-rich oxygen isotopes 25O and 26O are investigated experimentally and theoret- ically. In this first R3B-LAND experiment, the unbound states are populated at GSI via proton- knockout reactions from 26F and 27F at relativistic energies around 450 MeV/nucleon. From the kinematically complete measurement of the decay into 24O plus one or two neutrons, the 25O ground- state energy and lifetime are determined, and upper limits for the 26O ground state are extracted. In addition, the results provide evidence for an excited state in 26O at around 4 MeV. The ex- perimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.

Published
2012
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3. Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Author

Atar, L, Paschalis, S, Barbieri, C, Bertulani, CA, Diaz Fernandez, P, Holl, M, Najafi, MA, Panin, V, Alvarez-Pol, H, Aumann, T, Avdeichikov, V, Beceiro-Novo, S, Bemmerer, D, Benlliure, J, Boillos, JM, Boretzky, K, Borge, MJG, Caamano, M, Caesar, C, Casarejos, E, Catford, W, Cederkall, J, Chartier, M, Chulkov, L, Cortina-Gil, D, Cravo, E, Crespo, R, Dillmann, I, Elekes, Z, Enders, J, Ershova, O, Estrade, A, Farinon, F, Fraile, LM, Freer, M, Galaviz Redondo, D, Geissel, H, Gernhaeuser, R, Golubev, P, Goebel, K, Hagdahl, J, Heftrich, T, Heil, M, Heine, M, Heinz, A, Henriques, A, Hufnagel, A, Ignatov, A, Johansson, HT, Jonson, B, Kahlbow, J, Kalantar-Nayestanaki, N, Kanungo, R, Kelic-Heil, A, Knyazev, A, Kroell, T, Kurz, N, Labiche, M, Langer, C, Le Bleis, T, Lemmon, R, Lindberg, S, Machado, J, Marganiec-Galazka, J, Movsesyan, A, Nacher, E, Nikolskii, EY, Nilsson, T, Nociforo, C, Perea, A, Petri, M, Pietri, S, Plag, R, Reifarth, R, Ribeiro, G, Rigollet, C, Rossi, DM, Roeder, M, Savran, D, Scheit, H, Simon, H, Sorlin, O, Syndikus, I, Taylor, JT, Tengblad, O, Thies, R, Togano, Y, Vandebrouck, M, Velho, P, Volkov, V, Wagner, A, Wamers, F, Weick, H, Wheldon, C, Wilson, GL, Winfield, JS, Woods, P, Yakorev, D, Zhukov, M, Zilges, A, Zuber, K, and Collaboration, R3B

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B/LAND setup with incident beam energies in the range of 300–450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.

Published
2018

4. Quasifree ($p,pN$) scattering of light neutron-rich nuclei near $N=14$

Author

Díaz Fernández, P., Alvarez-Pol, H., Crespo, R., Cravo, E., Atar, L., Deltuva, A., Aumann, T., Avdeichikov, V., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C.A., Boillos, J.M., Boretzky, K., Borge, M.J.G., Caamaño, M., Cabanelas, P., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chartier, M., Chulkov, L.V., Cortina-Gil, D., Datta Pramanik, U., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estradé, A., Farinon, F., Fernández-Domínguez, B., Fraile, L.M., Freer, M., Galaviz, D., Geissel, H., Gernhäuser, R., Golubev, P., Göbel, K., Hagdahl, J., Heftrich, T., Heil, M., Heine, M., Heinz, A., Henriques, A., Holl, M., Hufnagel, A., Ignatov, A., Johansson, H.T., Jonson, B., Jurčiukonis, D., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Knyazev, A., Kröll, T., Kurz, N., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lindberg, S., Machado, J., Marganiec, J., Moro, A.M., Movsesyan, A., Nacher, E., Najafi, A., Nikolskii, E., Nilsson, T., Nociforo, C., Panin, V., Paschalis, S., Perea, A., Petri, M., Pietras, B., Pietri, S., Plag, R., Reifarth, R., Ribeiro, G., Rigollet, C., Rossi, D., Röder, M., Savran, D., Scheit, H., Simon, H., Sorlin, O., Syndikus, I., Taylor, J.T., Tengblad, O., Thies, R., Togano, Y., Vandebrouck, M., Velho, P., Volkov, V., Wagner, A., Wamers, F., Weick, H., Wheldon, C., Wilson, G., Winfield, J.S., Woods, P., Yakorev, D., Zhukov, M., Zilges, A., Zuber, K., Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

International audience; Background: For many years, quasifree scattering reactions in direct kinematics have been extensively used to study the structure of stable nuclei, demonstrating the potential of this approach. The RB3 collaboration has performed a pilot experiment to study quasifree scattering reactions in inverse kinematics for a stable C12 beam. The results from that experiment constitute the first quasifree scattering results in inverse and complete kinematics. This technique has lately been extended to exotic beams to investigate the evolution of shell structure, which has attracted much interest due to changes in shell structure if the number of protons or neutrons is varied. Purpose: In this work we investigate for the first time the quasifree scattering reactions (p,pn) and (p,2p) simultaneously for the same projectile in inverse and complete kinematics for radioactive beams with the aim to study the evolution of single-particle properties from N=14 to N=15. Method: The structure of the projectiles O23, O22, and N21 has been studied simultaneously via (p,pn) and (p,2p) quasifree knockout reactions in complete inverse kinematics, allowing the investigation of proton and neutron structure at the same time. The experimental data were collected at the R3B-LAND setup at GSI at beam energies of around 400 MeV/u. Two key observables have been studied to shed light on the structure of those nuclei: the inclusive cross sections and the corresponding momentum distributions. Conclusions: The knockout reactions (p,pn) and (p,2p) with radioactive beams in inverse kinematics have provided important and complementary information for the study of shell evolution and structure. For the (p,pn) channels, indications of a change in the structure of these nuclei moving from N=14 to N=15 have been observed, i.e., from the 0d5/2 shell to the 1s1/2. This supports previous observations of a subshell closure at N=14 for neutron-rich oxygen isotopes and its weakening for the nitrogen isotopes.

Published
2018
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5. Quasifree ($p$, $2p$) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Author

Atar, Leyla, Paschalis, Stefanos, Barbieri, C., Bertulani, C. A., Fernández, P. Díaz, Holl, M., Najafi, M.A, Panin, V., Alvarez-Pol, H., Aumann, T., Avdeichikov, V., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Boillos, J.M., Boretzky, K., Borge, M. J. G., Caamaño, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chartier, M., Chulkov, L., Cortina-Gil, D., Cravo, E., Crespo, R., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L.M, Freer, M., Redondo, D. Galaviz, Geissel, H., Gernhäuser, R., Golubev, P., Göbel, K., Hagdahl, J., Heftrich, T., Heil, M., Heine, M., Heinz, A., Henriques, A., Hufnagel, A., Ignatov, A., Johansson, H.T, Jonson, B, Kahlbow, J., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Knyazev, A., Kröll, T., Kurz, N., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lindberg, S., Machado, J., Marganiec-Gałązka, J., Movsesyan, A., Nacher, E., Nikolskii, E.Y., Nilsson, T., Nociforo, C., Perea, A., Petri, Marina, Pietri, S., Plag, R., Reifarth, R., Ribeiro, G., Rigollet, C., Rossi, D.M., Röder, M., Savran, D., Scheit, H., Simon, H., Sorlin, O., Syndikus, I., Taylor, J. T., Tengblad, O, Thies, R., Togano, Y., Vandebrouck, M., Velho, P., Volkov, V., Wagner, A., Wamers, F., Weick, H., Wheldon, C., Wilson, G.L., Winfield, J.S., Woods, P., Yakorev, D., Zhukov, M., Zilges, A., Zuber, K, 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), 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), 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), Helmholtz Centre for Heavy Ion Research, Department of Energy (US), National Science Foundation (US), Ministerio de Economía y Competitividad (España), Science and Technology Facilities Council (UK), Federal Ministry of Education and Research (Germany), University of Leicester, and Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Nuclear Theory, ddc:550, Aucun, Nuclear Experiment
Abstract

7 pags., 4 figs., tab., Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the (RB)-B-3/LAND setup with incident beam energies in the range of 300-450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type O-A(p,2p)NA-1 have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry., This work was supported by the German Federal Ministry for Education and Research (BMBF project 05P15RDFN1), and through the GSI-TU Darmstadt cooperation agreement. The work of C. B., W. C., and G.W. was supported by the United Kingdom Science and Technology Facilities Council (STFC) under Grants No. ST/L005743/1 and No. ST/P005314/1. SCGF calculations were performed at the DiRAC Complexity system of the University of Leicester (BIS National E-1023 infrastructure capital Grant No. ST/K000373/1 and STFC 1024 Grant No. ST/K0003259/1). C. A. B. acknowledges support by the U.S. DOE Grant No. DE-FG02- 08ER41533 and the U.S. NSF Grant No. 1415656. L. M. F. acknowledges funding from MINECO FPA2015-65035-P project.

Published
2018
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6. Effective proton-neutron interaction near the drip line from unbound states in $^{25,26}$F

Author

Vandebrouck, M., Lepailleur, A., Sorlin, O., Aumann, T., Caesar, C., Holl, M., Panin, V., Wamers, F., Stroberg, S. R., Holt, J. D., de Oliveira Santos, F., Alvarez-Pol, H., Atar, L., Avdeichikov, V., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Bogner, S. K., Boillos, J. M., Boretzky, K., Borge, M. J. G., Caamaño, M., Casarejos, E., Catford, W., Cederkäll, J., Chartier, M., Chulkov, L., Cortina-Gil, D., Cravo, E., Crespo, R., Datta Pramanik, U., Díaz Fernández, P., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estradé, A., Farinon, F., Fraile, L. M., Freer, M., Galaviz, D., Geissel, H., Gernhäuser, R., Gibelin, J., Golubev, P., Göbel, K., Hagdahl, J., Heftrich, T., Heil, M., Heine, M. (Marcel), Heinz, A., Henriques, A., Hergert, H., Hufnagel, A., Ignatov, A., Johansson, H. T., Jonson, B., Kahlbow, J., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Knyazev, A., Kröll, T., Kurz, N., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lindberg, S., Machado, J., Marganiec, J., Marqués, F. M., Movsesyan, A., Nacher, E., Najafi, M., Nikolskii, E., Nilsson, T., Nociforo, C., Paschalis, S., Perea, A., Petri, M., Pietri, S., Plag, R., Reifarth, R., Ribeiro, G., Rigollet, C., Röder, M., Rossi, D., Savran, D., Scheit, H., Schwenk, A., Simon, H., Syndikus, I., Taylor, J. T., Tengblad, O., Thies, R., Togano, Y., Velho, P., Volkov, V., Wagner, A., Weick, H., Wheldon, C., Wilson, G., Winfield, J. S., Woods, P., Yakorev, D., Zhukov, M., Zilges, A., Zuber, K., 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 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), 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), R3B Collaboration, 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)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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
21.10.-k, Nuclear Theory, Aucun, Coulomb dissociation radioactive beam, FOS: Physical sciences, Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment, 27.30.+t, 25.60.-t, 29.30.Hs
Abstract

Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The $^{26}$F nucleus, composed of a deeply bound $\pi0d\_{5/2}$ proton and an unbound $\nu0d\_{3/2}$ neutron on top of an $^{24}$O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a $J^{\pi} = 1^{+}\_1 - 4^{+}\_1$ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The $J^{\pi} = 1^{+}\_1, 2^{+}\_1,4^{+}\_1$ bound states have been determined, and only a clear identification of the $J^{\pi} =3^{+}\_1$ is missing.Purpose: We wish to complete the study of the $J^{\pi} = 1^{+}\_1 - 4^{+}\_1$ multiplet in $^{26}$F, by studying the energy and width of the $J^{\pi} =3^{+}\_1$ unbound state. The method was firstly validated by the study of unbound states in $^{25}$F, for which resonances were already observed in a previous experiment.Method: Radioactive beams of $^{26}$Ne and $^{27}$Ne, produced at about $440A$\,MeV by the FRagment Separator at the GSI facility, were used to populate unbound states in $^{25}$F and $^{26}$F via one-proton knockout reactions on a CH$\_2$ target, located at the object focal point of the R$^3$B/LAND setup. The detection of emitted $\gamma$-rays and neutrons, added to the reconstruction of the momentum vector of the $A-1$ nuclei, allowed the determination of the energy of three unbound states in $^{25}$F and two in $^{26}$F. Results: Based on its width and decay properties, the first unbound state in $^{25}$F is proposed to be a $J^{\pi} = 1/2^-$ arising from a $p\_{1/2}$ proton-hole state. In $^{26}$F, the first resonance at 323(33)~keV is proposed to be the $J^{\pi} =3^{+}\_1$ member of the $J^{\pi} = 1^{+}\_1 - 4^{+}\_1$ multiplet. Energies of observed states in $^{25,26}$F have been compared to calculations using the independent-particle shell model, a phenomenological shell-model, and the ab initio valence-space in-medium similarity renormalization group method.Conclusions: The deduced effective proton-neutron interaction is weakened by about 30-40\% in comparison to the models, pointing to the need of implementing the role of the continuum in theoretical descriptions, or to a wrong determination of the atomic mass of $^{26}$F., Comment: 14 pages, 7 figures, 3 tables, submitted to PRC

Published
2017
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7. Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

Author

Thies, R, Heinz, A, Adachi, T, Aksyutina, Y, Alcantara-Nunes, J, Altstadt, S, Alvarez-Pol, H, Ashwood, N, Aumann, T, Avdeichikov, V, Barr, M, Beceiro-Novo, S, Bemmerer, D, Benlliure, J, Bertulani, CA, Boretzky, K, Borge, MJG, Burgunder, G, Camano, M, Caesar, C, Casarejos, E, Catford, W, Cederkall, J, Chakraborty, S, Chartier, M, Chulkov, LV, Cortina-Gil, D, Crespo, R, Datta, U, Diaz Fernandez, P, Dillmann, I, Elekes, Z, Enders, J, Ershova, O, Estrade, A, Farinon, F, Fraile, LM, Freer, M, Freudenberger, M, Fynbo, HOU, Galaviz, D, Geissel, H, Gernhauser, R, Gobel, K, Golubev, P, Diaz, DG, Hagdahl, J, Heftrich, T, Heil, M, Heine, M, Henriques, A, Holl, M, Ickert, G, Ignatov, A, Jakobsson, B, Johansson, HT, Jonson, B, Kalantar-Nayestanaki, N, Kanungo, R, Knobel, R, Kroll, T, Krucken, R, Kurcewicz, J, Kurz, N, Labiche, M, Langer, C, Le Bleis, T, Lemmon, R, Lepyoshkina, O, Lindberg, S, Machado, J, Marganiec, J, Maroussov, V, Mostazo, M, Movsesyan, A, Najafi, A, Nilsson, T, Nociforo, C, Panin, V, Paschalis, S, Perea, A, Petri, M, Pietri, S, Plag, R, Prochazka, A, Rahaman, A, Rastrepina, G, Reifarth, R, Ribeiro, G, Ricciardi, MV, Rigollet, C, Riisager, K, Roder, M, Rossi, D, Sanchez del Rio, J, Savran, D, Scheit, H, Simon, H, Sorlin, O, Stoica, V, Streicher, B, Taylor, JT, Tengblad, O, Terashima, S, Togano, Y, Uberseder, E, Van de Walle, J, Velho, P, Volkov, V, Wagner, A, Wamers, F, Weick, H, Weigand, M, Wheldon, C, Wilson, G, Wimmer, C, Winfield, JS, Woods, P, Yakorev, D, Zhukov, MV, Zilges, A, Zuber, K, Collaboration, R, 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), R3B Collaboration, KVI - Center for Advanced Radiation Technology, Research unit Nuclear & Hadron Physics, Federal Ministry of Education and Research (Germany), Nuclear Astrophysics Virtual Institute (Germany), Helmholtz Association, Science and Technology Facilities Council (UK), Department of Energy (US), Ministerio de Economía y Competitividad (España), Swedish Research Council, Helmholtz Centre for Heavy Ion Research, National Science Foundation (US), 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, Ion beam, 010308 nuclear & particles physics, Fission, Projectile, Nuclear Theory, Fragmentation (computing), Aucun, FOS: Physical sciences, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Nuclear physics, nuclear fragmentation fission radioactive ion beam facilities C10 C12−18 B10−15 isotope, 0103 physical sciences, Neutron, Física nuclear, Nuclear Experiment (nucl-ex), 010306 general physics, Nucleon, Nuclear Experiment, Excitation, Beam (structure)
Abstract

R. Thies et al.; 9 pags., 7 figs., 1 tab., Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions. Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes. Method: We have measured projectile fragments from C10,12-18 and B10-15 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations. Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic C10,12-18 and B10-15 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well. Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study. ©2016 American Physical Society, We thank the FRS and the GSI accelerator staff for their efforts. This work was supported by the Swedish Research Council. O.T. was supported by the Spanish Research Council under project FPA2012-32443, C.A.B. acknowledges support from the U.S. DOE Grant No. DE-FG02-08ER41533 and the U.S. NSF Grant No. 1415656. L.M.F. acknowledges support by the Spanish Research Council under project FPA2013-41267-P and M.R. was supported by GSI (F&E, DR-ZUBE), German BMBF (06DR134I and 05P09CRFN5), the Nuclear Astrophysics Virtual Institute (NAVI, HGF VHVI- 417) and the Helmholtz Association Detector Technology and Systems Platform. T.K. acknowledges support by the German BMBF No. 06DA9040I, No. 05P12RDFN8, and No. 05P15RDFN1. C.W. acknowledges funding by the UK STFC No. ST/E500651/1, while N.A. and M.F. acknowledge funding by the UK STFC No. ST/F011989/1.

Published
2016
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8. Efficiency determination of resistive plate chambers for fast quasi-monoenergetic neutrons

Author

Röder, M., Elekes, Z., Aumann, T., Bemmerer, D., Boretzky, K., Caesar, C., Cowan, T. E., Hehner, J., Heil, M., Kempe, M., Maroussov, V., Nusair, O., Prokofiev, A. V., Reifarth, R., Sobiella, M., Stach, D., Wagner, A., Yakorev, D., Zilges, A., Zuber, K., and for the R3B Collaboration

Subjects
Physics::Instrumentation and Detectors, Nuclear Theory, Nuclear Experiment
Abstract

Composite detectors made of stainless-steel converters and multigap resistive plate chambers have been irradiated with quasi-monoenergetic neutrons with a peak energy of 175 MeV. The neutron detection efficiency has been determined using two different methods. The data are in agreement with the output of Monte Carlo simulations. The simulations are then extended to study the response of a hypothetical array made of these detectors to energetic neutrons from a radioactive ion beam experiment.

Published
2014

9. Beyond the neutron drip line: The unbound oxygen isotopes O-25 and O-26

Author

Caesar, C., Simonis, J., Adachi, T., Aksyutina, Y., Alcantara, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Aumann, T., Avdeichikov, V., Barr, M., Beceiro, S., Bemmerer, D., Benlliure, J., Bertulani, C., Boretzky, K., Borge, M., Burgunder, G., Caamano, M., Casarejos, E., Catford, W., Cederkall, J., Chakraborty, S., Chartier, M., Chulkov, L., Cortina-Gil, D., Pramanik, U., Fernandez, P., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L., Freer, M., Freudenberger, M., Fynbo, H., Galaviz, D., Geissel, H., Gernhauser, R., Golubev, P., Diaz, D., Hagdahl, J., Heftrich, T., Heil, M., Heine, M., Heinz, A., Henriques, A., Holl, M., Holt, J., Ickert, G., Ignatov, A., Jakobsson, B., Johansson, H., Jonson, B., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Knobel, R., Kroll, T., Krucken, R., Kurcewicz, J., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lepyoshkina, O., Lindberg, S., Machado, J., Marganiec, J., Maroussov, V., Menendez, J., Mostazo, M., Movsesyan, A., Najafi, A., Nilsson, T., Nociforo, C., Panin, V., Perea, A., Pietri, S., Plag, R., Prochazka, A., Rahaman, A., Rastrepina, G., Reifarth, R., Ribeiro, G., Ricciardi, M., Rigollet, C., Riisager, K., Roder, M., Rossi, D., Del Rio, J., Savran, D., Scheit, H., Schwenk, A., Simon, H., Sorlin, O., Stoica, V., Streicher, B., Taylor, J., Tengblad, O., Terashima, S., Thies, R., Togano, Y., Uberseder, E., Walle, J., Velho, P., Volkov, V., Wagner, A., Wamers, F., Weick, H., Weigand, M., Wheldon, C., Wilson, G., Wimmer, C., Winfield, J., Woods, P., Yakorev, D., Zhukov, M., Zilges, A., Zoric, M., and Zuber, K.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The very neutron-rich oxygen isotopes O-25 and O-26 are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via proton-knockout reactions from F-26 and F-27 at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into O-24 plus one or two neutrons, the O-25 ground-state energy and width are determined, and upper limits for the O-26 ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in O-26 at around 4 MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.

Published
2013

10. Electromagnetic dipole strength of 136Ba below the neutron separation energy

Author

Massarczyk, R., Schwengner, R., Dönau, F., Litvinova, E., Rusev, G., Beyer, R., Hannaske, R., Junghans, A. R., Kempe, M., Kelley, J. H., Kögler, T., Kosev, K., Kwan, E., Marta, M., Matic, A., Nair, C., Raut, R., Schilling, K. D., Schramm, G., Stach, D., Tonchev, A. P., Tornow, W., Trompler, E., Yakorev, D., and Wagner, A.

Subjects
nuclear spectroscopy, gamma strength function, Nuclear Theory, nuclear structure, Physics::Accelerator Physics, Photon scattering, Nuclear Experiment
Abstract

The electromagnetic dipole strength of the nucleus 136Ba has been investigated at two facilities. At the bremsstrahlung facility at the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf, two measurements were performed with electron energies of 7.0 and 11.4 MeV. Photon scattering on the same nucleus has been investigated at the HI$gS facility of the Triangle Universities Nuclear Laboratory. The GEANT4 code has been used to determine detector response and non-nuclear scattered events. Thus it is possible to account for the dipole strength in the quasi-continuum of unresolvable transitions. A statistical code was used to simulate inelastic transitions and to determine the branching ratios of transitions to the ground-state. The resulting photo-absorption cross section is compared to QRPA and RQTBA calculations.

Published
2012

11. NeuLAND - Concepts for the Detection of Fast Neutrons

Author

Aumann, T., Basu, P., Bemmerer, D., Bertini, D., Blanco, A., Boretzky, K., Caesar, C., Chakraborty, S., Chatterjee, S., Cherciu, M., Datta Pramanik, U., Elekes, Z., Fonte, P., Galaviz, D., Gonzalez Diaz, D., Haiduc, M., Hehner, J., Heil, M., Ignatov, A., Kempe, M., Leifels, Y., Machado, J., Maroussov, V., Panja, J., Potlog, M., Rahaman, A., Reifarth, R., R. ̈Oder, M., Rossi, D., Simon, H., Sobiella, M., Stach, D., Stan, E., Teubig, P., Wagner, A., Yakorev, D., Zilges, A., and Zuber, K.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The acronym NeuLAND (new Large Area Neutron De-tector) stands for the high-efficiency time-of-flight spectrometer for high-energy neutrons (200 to 1000 MeV) within the R3B experiment being designed for FAIR. A spatial resolution of approximately sigma~1 cm and a time resolution of approximately sigma~100 ps are envisaged together with an efficiency of more than 90 % for one-neutron events, as well as a high multi-neutron recognition capability.

Published
2011

12. Fast Neutron Cross-Section Measurements with the nELBE Neutron Time-of-Flight Facility

Author

Wagner, A., Bemmerer, D., Beyer, R., Birgersson, E., Ferrari, A., Grosse, E., Hannaske, R., Junghans, A. R., Kempe, M., Kögler, T., Marta, M., Matic, A., Nolte, R., Schilling, K. D., Schramm, G., Schwengner, R., Weiss, F.-P., and Yakorev, D.

Subjects
Nuclear Theory, Physics::Accelerator Physics, Nuclear Experiment
Abstract

At the Forschungszentrum Dresden-Rossendorf a new neutron time-of-flight facility has been set up. Fast neutrons in the energy range from 0.1 MeV to 10 MeV are produced using pulsed electron beams from a superconducting electron linear accelerator. Short beam pulses of less than 10 ps allow high-resolution time-of-flight experiments with the aim to determine interaction cross sections of neutrons with reactor structural materials and actinides at energies matching the neutron energies in fast reactors. Following experiments using a thermionic electron injector a new superconducting radio-frequency injector has been built which will allow average beam currents of 0.5 mA at a repetition rate of 500 kHz. Meanwhile, first experiments on inelastic neutron scattering cross sections on 56Fe and total neutron cross sections on aluminium and tantalum have been performed as benchmark experiments. While photons from the de-exciting transitions are being detected using a 16-element BaF2 scintillator array, neutrons are measured with five low-threshold plastic scintillation detectors. Beam normalisation is done using a calibrated 235U fission chamber. The preparation of actinide targets for neutron induced fission cross section measurements is under way.

Published
2010

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