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1. Magicity versus superfluidity around $^{28}$O viewed from the study of $^{30}$F

Author

Kahlbow, J., Aumann, T., Sorlin, O., Kondo, Y., Nakamura, T., Nowacki, F., Revel, A., Achouri, N. L., Falou, H. Al, Atar, L., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Delaunay, F., Delbart, A., Deshayes, Q., Dombradi, Z., Douma, C. A., Elekes, Z., Gasparic, I., Gheller, J. -M., Gibelin, J., Gillibert, A., Harakeh, M. N., Hirayama, A., Holl, M., Horvat, A., Horvath, A., Hwang, J. W., Isobe, T., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., Körper, D., Koyama, S., Kuti, I., Lapoux, V., Lindberg, S., Marques, F. M., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M., Nakano, K., Nakatsuka, N., Nilsson, T., Obertelli, A., Orr, N. A., Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Rossi, D. M., Saito, A. T., Saito, T., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimada, K., Shimizu, Y., Simon, H., Sohler, D., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., Törnqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Wang, H., Yang, Z., Yasuda, M., and Yoneda, K.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

The neutron-rich unbound fluorine isotope $^{30}$F$_{21}$ has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasi-free proton knockout reaction of $^{31}$Ne nuclei at 235 MeV/nucleon. The mass and thus one-neutron-separation energy of $^{30}$F has been determined to be $S_n = -472\pm 58 \mathrm{(stat.)} \pm 33 \mathrm{(sys.)}$ keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in $S_n$($^{30}$F) shows that the ``magic'' $N=20$ shell gap is not restored close to $^{28}$O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron $d$ and $fp$ orbitals, with the $1p_{3/2}$ and $1p_{1/2}$ orbitals becoming more bound than the $0f_{7/2}$ one. This degeneracy and reordering of orbitals has two potential consequences: $^{28}$O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both $^{29,31}$F appear to be good two-neutron halo-nucleus candidates., Comment: 9 pages, 2 figures, accepted for publication in Physical Review Letters

Published
2024
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2. Intruder configurations in $^{29}$Ne at the transition into the island of inversion: Detailed structure study of $^{28}$Ne

Author

Wang, H., Yasuda, M., Kondo, Y., Nakamura, T., Tostevin, J. A., Ogata, K., Otsuka, T., Poves, A., Shimizu, N., Yoshida, K., Achouri, N. L., Falou, H. Al, Atar, L., Aumann, T., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Crawford, H. L., Delaunay, F., Delbart, A., Deshayes, Q., Dombrádi, Zs., Douma, C., Elekes, Z., Fallon, P., Gašparić, I., Gheller, J. -M., Gibelin, J., Gillibert, A., Harakeh, M. N., Hirayama, A., Hoffman, C. R., Holl, M., Horvat, A., Horváth, Á., Hwang, J. W., Isobe, T., Kahlbow, J., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., Körper, D., Koyama, S., Kuti, I., Lapoux, V., Lindberg, S., Marqués, F. M., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M. A., Nakano, K., Nakatsuka, N., Nilsson, T., Obertelli, A., Santos, F. de Oliveira, Orr, N. A., Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Revel, A., Rossi, D., Saito, A. T., Saito, T., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimizu, Y., Simon, H., Sohler, D., Sorlin, O., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., Törnqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Yang, Z., and Yoneda, K.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

Detailed $\gamma$-ray spectroscopy of the exotic neon isotope $^{28}$Ne has been performed for the first time using the one-neutron removal reaction from $^{29}$Ne on a liquid hydrogen target at 240~MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $^{28}$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder $p$-wave strength providing evidence of the breakdown of the $N=20$ and $N=28$ shell gaps. Only a weak, possible $f$-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large $p$-wave and small $f$-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Published
2023
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3. Border of the Island of Inversion: Unbound states in $^{29}$Ne

Author

Holl, M., Lindberg, S., Heinz, A., Kondo, Y., Nakamura, T., Tostevin, J. A., Wang, H., Nilsson, T., Achouri, N. L., Falou, H. Al, Atar, L., Aumann, T., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Crawford, H. L., Delaunay, F., Delbart, A., Deshayes, Q., Fernández, P. Díaz, Dombrádi, Z., Douma, C. A., Elekes, 13 Z., Fallon, P., Gašparić, I., Gheller, J. -M., Gibelin, J., Gillibert, A., Harakeh, M. N., Hirayama, A., Hoffman, C. R., Horvat, A., Horváth, Á., Hwang, J. W., Isobe, T., Kahlbow, J., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., Körper, D., Koyama, S., Kuti, I., Lapoux, V., Marqués, F. M., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M., Nakano, K., Nakatsuka, N., Obertelli, A., Santos, F. de Oliveira, Orr, N. A., Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Revel, A., Rossi, D., Saito, A. T., Saito, T. Y., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimizu, Y., Simon, H., Sohler, D., Sorlin, O., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., Törnqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Yang, Z., Yasuda, M., and Yoneda, K.

Subjects
Nuclear Experiment
Abstract

The nucleus $^{29}$Ne is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder $f_{7/2}$-state, which would place $^{29}$Ne firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of $^{29}$Ne is reported. The states were populated in $^{30}\mathrm{Ne}(p,pn)$ and $^{30}\mathrm{Na}(p,2p)$ reactions at a beam energy of around $230$ MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing $\ell$-assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant $\ell$=3-component, giving first evidence for $f_{7/2}$ single particle strength in $^{29}$Ne. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction, Comment: 12 pages, 14 figures, accepted for publication in Physical Review C

Published
2022
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4. Extending the Southern Shore of the Island of Inversion to $^{28}$F

Author

Revel, A., Sorlin, O., Marques, F. M., Kondo, Y., Kahlbow, J., Nakamura, T., Orr, N. A., Nowacki, F., Tostevin, J. A., Yuan, C. X., Achouri, N. L., Falou, H. Al, Atar, L., Aumann, T., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Crawford, H. L., Delaunay, F., Delbart, A., Deshayes, Q., Dombradi, Z., Douma, C. A., Elekes, Z., Fallon, P., Gasparic, I., Gheller, J. -M., Gibelin, J., Gillibert, A., Harakeh, M. N., He, W., Hirayama, A., Hoffman, C. R., Holl, M., Horvat, A., Horvath, A., Hwang, J. W., Isobe, T., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., Korper, D., Koyama, S., Kuti, I., Lapoux, V., Lindberg, S., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M., Nakano, K., Nakatsuka, N., Nilsson, T., Obertelli, A., Santos, F. de Oliveira, Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Rossi, D., Saito, A. T., Saito, T., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimizu, Y., Simon, H., Sohler, D., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., Tornqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Yang, Z., Yasuda, M., and Yoneda, K.

Subjects
Nuclear Experiment
Abstract

Detailed spectroscopy of the neutron-unbound nucleus $^{28}$F has been performed for the first time following proton/neutron removal from $^{29}$Ne/$^{29}$F beams at energies around 230 MeV/nucleon. The invariant-mass spectra were reconstructed for both the $^{27}$F$^{(*)}+n$ and $^{26}$F$^{(*)}+2n$ coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the $^{28}$F ground state, with $S_n(^{28}$F$)=-199(6)$ keV, while analysis of the $2n$ decay channel allowed a considerably improved $S_n(^{27}$F$)=1620(60)$ keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of $^{28}$F. Importantly, in the case of the ground state, the reconstructed $^{27}$F$+n$ momentum distribution following neutron removal from $^{29}$F indicates that it arises mainly from the $1p_{3/2}$ neutron intruder configuration. This demonstrates that the island of inversion around $N=20$ includes $^{28}$F, and most probably $^{29}$F, and suggests that $^{28}$O is not doubly magic., Comment: 6 pages, 3 figures, Supplemental Material, accepted for publication in Physical Review Letters

Published
2020
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5. Strong neutron pairing in core+4n nuclei

Author

Revel, A., Marques, F. M., Sorlin, O., Aumann, T., Caesar, C., Holl, M., Panin, V., Vandebrouck, M., Wamers, F., Alvarez-Pol, H., Atar, L., Avdeichikov, V., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boillos, J. M., Boretzky, K., Borge, M. J. G., Caamano, M., Casarejos, E., Catford, W. N., Cederkäll, J., Chartier, M., Chulkov, L., Cortina-Gil, D., Cravo, E., Crespo, R., Pramanik, U. Datta, Fernandez, P. Diaz, Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L. M., Freer, M., Galaviz, D., Geissel, H., Gernhauser, 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., Kroll, T., Kurz, N., Labiche, M., Langer, C., Bleis, T. Le, Lemmon, R., Lindberg, S., Machado, J., Marganiec, J., 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., Roder, M., Rossi, D., Savran, D., Scheit, H., 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., and Zuber, K.

Subjects
Nuclear Experiment
Abstract

The emission of neutron pairs from the neutron-rich $N\!=\!12$ isotones $^{18}$C and $^{20}$O has been studied by high-energy nucleon knockout from $^{19}$N and $^{21}$O secondary beams, populating unbound states of the two isotones up to 15~MeV above their two-neutron emission thresholds. The analysis of triple fragment-$n$-$n$ correlations shows that the decay $^{19}$N$(-1p)^{18}$C$^*\!\rightarrow^{16}$C+$n$+$n$ is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a $^{14}$C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay $^{21}$O$(-1n)^{20}$O$^*\!\rightarrow^{18}$O+$n$+$n$, attributed to its formation through the knockout of a deeply-bound neutron that breaks the $^{16}$O core and reduces the number of pairs., Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev. Lett

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., Santos, F. De Oliveira, 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., Caamano, M., Casarejos, E., Catford, W., Cederkäll, J., Chartier, M., Chulkov, L., Cortina-Gil, D., Cravo, E., Crespo, R., Pramanik, U. Datta, Fernandez, P. Diaz, Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L. M., Freer, M., Galaviz, D., Geissel, H., Gernhauser, R., Gibelin, J., Golubev, P., Göbel, K., Hagdahl, J., Heftrich, T., Heil, M., Heine, M., 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., Bleis, T. Le, Lemmon, R., Lindberg, S., Machado, J., Marganiec, J., Marques, 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., 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., and Zuber, K.

Subjects
Nuclear Experiment
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. Determination of the Neutron-Capture Rate of 17C for the R-process Nucleosynthesis

Author

Heine, M., Typel, S., Wu, M. -R., Adachi, T., Aksyutina, Y., Alcantara, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Aumann, T., Avdeichikov, V., Barr, M., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boretzky, K., Borge, M. J. G., Burgunder, G., Caamano, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chakraborty, S., Chartier, M., Chulkov, L. V., Cortina-Gil, D., Crespo, R., 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., Göbel, K., Golubev, P., Diaz, D. Gonzalez, Hagdahl, J., Heftrich, T., Heil, M., Heinz, A., Henriques, A., Holl, M., 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., Kurz, N., Labiche, M., Langer, C., Bleis, T. Le, Lemmon, R., Lepyoshkina, O., Lindberg, S., Machado, J., Marganiec, J., Martínez-Pinedo, G., Maroussov, V., Mostazo, M., Movsesyan, A., Najafi, A., Neff, T., 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, M. V., Rigollet, C., Riisager, K., Röder, M., Rossi, D., del Rio, J. Sanchez, Savran, D., Scheit, H., Simon, H., Sorlin, O., Stoica, V., Streicher, B., Taylor, J. T., 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., and Zuber, K.

Subjects
Nuclear Experiment, Astrophysics - Solar and Stellar Astrophysics
Abstract

With the R$^{3}$B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of $^{18}$C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of $^{17}$C into the ground state of $^{18}$C. Those data have been used to constrain theoretical calculations for transitions populating excited states in $^{18}$C. This allowed to derive the astrophysical cross section $\sigma^{*}_{\mathrm{n}\gamma}$ accounting for the thermal population of $^{17}$C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures $T_{9}\leq{}1$~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of $^{17}$C on the production of second- and third-peak elements in contrast to earlier sensitivity studies.

Published
2016
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8. Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

Author

Thies, R., Heinz, A., Adachi, T., Aksyutina, Y., Alcantara-Núñes, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Aumann, T., Avdeichikov, V., Barr, M., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boretzky, K., Borge, M. J. G., Burgunder, G., Caamano, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chakraborty, S., Chartier, M., Chulkov, L. V., Cortina-Gil, D., Crespo, R., Datta, U., Fernández, P. Díaz, Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estradé, A., Farinon, F., Fraile, L. M., Freer, M., Freudenberger, M., Fynbo, H. O. U., Galaviz, D., Geissel, H., Gernhäuser, R., Göbel, K., Golubev, P., Diaz, D. Gonzalez, Hagdahl, J., Heftrich, T., Heil, M., Heine, M., Henriques, A., Holl, M., Ickert, G., Ignatov, A., Jakobsson, B., Johansson, H. T., Jonson, B., Kalantar-Nayestanaki, N., Kanungo, R., Knöbel, R., Kröll, T., Krücken, R., Kurcewicz, J., Kurz, N., Labiche, M., Langer, C., Bleis, T. Le, 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, M. V., Rigollet, C., Riisager, K., Röder, M., Rossi, D., del Rio, J. Sanchez, Savran, D., Scheit, H., Simon, H., Sorlin, O., Stoica, V., Streicher, B., Taylor, J. T., 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, J. S., Woods, P., Yakorev, D., Zhukov, M. V., Zilges, A., and Zuber, K.

Subjects
Nuclear Experiment
Abstract

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 to reach 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 10,12-18C and 10-15B isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent dataset. We compare our data to model calculations. Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic 10,12-18C and 10-15B isotopes impinging on a carbon target. Comparing model calculations to the data, we find that EPAX 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 have allowed for 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.

Published
2016
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9. 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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10. Border of the island of inversion: Unbound states in 29 Ne

Author

Holl, M., Lindberg, S., Heinz, A., Kondo, Y., Nakamura, T., Tostevin, J. A., Wang, H., Nilsson, T., Achouri, N. L., Al Falou, H., Atar, L., Aumann, T., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Crawford, H. L., Delaunay, F., Delbart, A., Deshayes, Q., D��az Fern��ndez, P., Dombr��di, Z., Douma, C. A., Elekes, Z., Fallon, P., Ga��pari��, I., Gheller, J.-M., Gibelin, J., Gillibert, A., Harakeh, M. N., Hirayama, A., Hoffman, C. R., Horvat, A., Horv��th, ��., Hwang, J. W., Isobe, T., Kahlbow, J., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., K��rper, D., Koyama, S., Kuti, I., Lapoux, V., Marqu��s, F. M., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M., Nakano, K., Nakatsuka, N., Obertelli, A., de Oliveira Santos, F., Orr, N. A., Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Revel, A., Rossi, D., Saito, A. T., Saito, T. Y., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimizu, Y., Simon, H., Sohler, D., Sorlin, O., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., T��rnqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Yang, Z., Yasuda, M., Yoneda, K., 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 de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, 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), SAMURAI21, Research unit Nuclear & Hadron Physics, and Nuclear Energy

Subjects
Physics, FOS: Physical sciences, Nuclear structure, direct reactions, radioactive beams, ddc:530, Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

The nucleus $^{29}$Ne is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder $f_{7/2}$-state, which would place $^{29}$Ne firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of $^{29}$Ne is reported. The states were populated in $^{30}\mathrm{Ne}(p,pn)$ and $^{30}\mathrm{Na}(p,2p)$ reactions at a beam energy of around $230$ MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing $\ell$-assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant $\ell$=3-component, giving first evidence for $f_{7/2}$ single particle strength in $^{29}$Ne. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction, Comment: 12 pages, 14 figures, accepted for publication in Physical Review C

Published
2022
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11. 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

12. 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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13. Structure of $^{13}$Be studied in proton knockout from $^{14}$B

Author

Ribeiro, G., Nácher, E., Tengblad, O., Díaz Fernández, P., Aksyutina, Y., Alvarez-Pol, H., Atar, L., Aumann, T., Avdeichikov, V., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boillos, J. M., Boretzky, K., Borge, M. J. G., Caamano, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chartier, M., Chulkov, L., Cortina-Gil, D., Cravo, E., Crespo, R., Datta Pramanik, U., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fraile, L. M., Freer, M., Fynbo, H. O. U., 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., Kalantar-Nayestanaki, N., Kanungo, R., Kelic-Heil, A., Kurz, N., Kröll, T., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lindberg, S., Machado, J., Marganiec, J., Movsesyan, A., Nilsson, T., Nociforo, C., Panin, V., Paschalis, S., Perea, A., Petri, M., Pietri, S., Plag, R., Reifarth, R., Rigollet, C., Riisager, K., Rossi, D., Röder, M., Savran, D., Scheit, H., Simon, H., Sorlin, O., Syndikus, I., Taylor, J. T., Thies, R., Velho, P., Wagner, A., Wamers, F., Vandebrouck, M., Weick, H., Wheldon, C., Wilson, G., Wimmer, C., Winfield, J. S., Woods, P., Zhukov, M. V., Zilges, A., Zuber, K., 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), R$^3$B, 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
radioactive beams, nuclear structure, Nuclear Theory, Aucun, 13Be, Nuclear Reactions, unbound nuclei, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

Physical review / C 98(2), 024603 (2018). doi:10.1103/PhysRevC.98.024603, Published by Inst., Woodbury, NY

Published
2018
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14. Quasi-free (p,pN) scattering of light neutron-rich nuclei around N = 14

Author

Diaz Fernandez, 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., Caamano, M., Cabanelas, P., Caesar, C., Casarejos, E., Catford, W., Cederkall, J., Chartier, M., Chulkov, L. V., Cortina-Gil, D., Datta Pramanik, U., Dillmann, I., Elekes, Z., Enders, J., Ershova, O., Estrade, A., Farinon, F., Fernandez-Dominguez, 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., Jurciukonis, 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., and Zuber, K.

Subjects
quasi-free scattering reactions radioactive beams single-particle, Nuclear Experiment
Abstract

In this work we investigate for the first time the quasi-free 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.

Published
2018

15. 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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16. Determination of the Neutron-Capture Rate of 17C for the R-process Nucleosynthesis

Author

Heine, M., Typel, S., Wu, M.-R., Adachi, T., Aksyutina, Y., Alcantara, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Avdeichikov, T. A. V., Barr, M., Beceiro-Novo, S., Bemmerer, D., Benlliure, J., Bertulani, C. A., Boretzky, K., Borge, M. J. G., Burgunder, G., Caamano, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chakraborty, S., Chartier, M., Chulkov, L. V., Cortina-Gil, D., Crespo, R., Datta Pramanik, U., Diaz Fernandez, P., 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., Göbel, K., Golubev, P., Gonzalez Diaz, D., Hagdahl, J., Heftrich, T., Heil, M., Heinz, A., Henriques, A., Holl, M., 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., Kurz, N., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lepyoshkina, O., Lindberg, S., Machado, J., Marganiec, J., Martínez-Pinedo, G., Maroussov, V., Mostazo, M., Movsesyan, A., Najafi, A., Neff, T., 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, M. V., Rigollet, C., Riisager, K., Röder, M., Rossi, D., Sanchez Del Rio, J., Savran, D., Scheit, H., Simon, H., Sorlin (Ganil), O., Stoica, V., Streicher, B., Taylor, J. T., 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. S., Woods, P., Yakorev, D., Zhukov, M. V., Zilges, A., and Zuber, K.

Subjects
r-process, nucleosynthesis, Coulomb dissociation, Nuclear Experiment, radiative neutron capture
Abstract

With the R3B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of 18C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of 17C into the ground state of 18C. Those data have been used to constrain theoretical calculations for transitions populating excited states in 18C. This allowed to derive the astrophysical cross section σ∗nγ accounting for the thermal population of 17C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures T9≤1~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of 17C on the production of second- and third-peak elements in contrast to earlier sensitivity studies.

Published
2017

17. Determination of the Neutron-Capture Rate of $^{17}$C for the R-process Nucleosynthesis

Author

Heine, M., Typel, S., Wu, M. -R, Adachi, T., Aksyutina, Y., Alcantara, J., Altstadt, S., Alvarez-Pol, H., Ashwood, N., Aumann, T., Avdeichikov, V., Barr, M., Beceiro-Novo, S., Daniel Bemmerer, Benlliure, J., Bertulani, C. A., Boretzky, K., Borge, M. J. G., Burgunder, G., Caamano, M., Caesar, C., Casarejos, E., Catford, W., Cederkäll, J., Chakraborty, S., Chartier, M., Chulkov, L. V., Cortina-Gil, D., Crespo, R., Datta Pramanik, U., Diaz Fernandez, P., 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., Göbel, K., Golubev, P., Gonzalez Diaz, D., Hagdahl, J., Heftrich, T., Heil, M., Heinz, A., Henriques, A., Holl, M., 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., Kurz, N., Labiche, M., Langer, C., Le Bleis, T., Lemmon, R., Lepyoshkina, O., Lindberg, S., Machado, J., Marganiec, J., Martínez-Pinedo, G., Maroussov, V., Mostazo, M., Movsesyan, A., Najafi, A., Neff, T., 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, M. V., Rigollet, C., Riisager, K., Röder, M., Rossi, D., Sanchez Del Rio, J., Savran, D., Scheit, H., Simon, H., Sorlin, O., Stoica, V., Streicher, B., Taylor, J. T., 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. S., Woods, P., Yakorev, D., Zhukov, M. V., Zilges, A., Zuber, K., Helmholtz zentrum für Schwerionenforschung GmbH (GSI), KVI-CART, University of Groningen, University of Groningen [Groningen], 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), R3B Collaboration, Research unit Nuclear & Hadron Physics, 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
astro-ph.SR, Astrophysics - Solar and Stellar Astrophysics, FOS: Physical sciences, Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], nucl-ex, Nuclear Experiment, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

International audience; With the R$^{3}$B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of $^{18}$C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of $^{17}$C into the ground state of $^{18}$C. Those data have been used to constrain theoretical calculations for transitions populating excited states in $^{18}$C. This allowed to derive the astrophysical cross section $\sigma^{*}_{\mathrm{n}\gamma}$ accounting for the thermal population of $^{17}$C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures $T_{9}\leq{}1$~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of $^{17}$C on the production of second- and third-peak elements in contrast to earlier sensitivity studies.

Published
2017
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18. Beta-delayed proton emission from 20Mg

Author

Lund, M. V., Andreyev, Andrei, Borge, M. J. G., Cederkäll, J., De Witte, H., Fraile, L. M., Fynbo, H. O. U., Greenlees, P. T., Harkness-Brennan, L. J., Howard, A. M., Huyse, M., Jonson, B., Judson, D. S., Kirsebom, O. S., Konki, J., Kurcewicz, J., Lazarus, I., Lica, R., Lindberg, S., Madurga, M., Marginean, N., Marginean, R., Marroquin, I., Mihai, C., Munch, M., Nacher, E., Negret, A., Nilsson, T., Page, R. D., Pascu, S., Perea, A., Pucknell, V., Rahkila, P., Rapisarda, E., Riisager, K., Rotaru, F., Sotty, C., Stanoiu, M., Tengblad, O., Turturica, A., Van Duppen, P., Vedia, V., Wadsworth, R., and Warr, N.

Subjects
Nuclear Experiment
Abstract

Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15O( $ \alpha$ , $ \gamma$ )19Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms.

Published
2016

19. 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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20. 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

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