Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Morales, A. I.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs; Pfützner, M.; Regan, P. H.; Rudolph, D.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; De Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R.P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C.L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; Klupp, S.

The neutron-rich isotopes Tl-211,Tl-213, beyond the N = 126 shell closure, have been studied for the first time in isomer gamma-ray decay, exploiting the fragmentation of a primary uranium beam at the Fragment Separator-Rare Isotopes Investigation at GSI setup. The observed isomeric states in Tl-211,Tl-213 show a deviation from the seniority-like scheme of Tl-209. The possible interpretation of the data is discussed on the basis of energy-level systematics and shell-model calculations.

The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the beta decay of neutron-rich nuclei just beyond Pb-208. This paper reports on beta-delayed gamma decays of Tl211-213, Pb-215, and Bi215-219 de-exciting states in the daughters Pb211-213, Bi-215, and Po215-219. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden beta transitions in this mass region is discussed.

A. Gottardo, 2, ∗ J.J. Valiente-Dobón, G. Benzoni, S. Lunardi, 4 A. Gadea, A. Algora, N. Al-Dahan, G. de Angelis, Y. Ayyad, D. Bazzacco, J. Benlliure, P. Boutachkov, M. Bowry, A. Bracco, 9 A.M. Bruce, M. Bunce, F. Camera, 9 E. Casarejos, M.L. Cortes, F.C.L. Crespi, A. Corsi, 9 A.M. Denis Bacelar, A.Y. Deo, C. Domingo-Pardo, M. Doncel, T. Engert, K. Eppinger, G.F. Farrelly, F. Farinon, E. Farnea, H. Geissel, J. Gerl, N. Goel, M. Górska, J. Grebosz, E. Gregor, T. Habermann, R. Hoischen, 15 R. Janik, S. Klupp, I. Kojouharov, N. Kurz, S.M. Lenzi, 4 S. Leoni, 9 S. Mandal, R. Menegazzo, D. Mengoni, B. Million, V. Modamio, A.I. Morales, D.R. Napoli, F. Naqvi, 18 R. Nicolini, 9 C. Nociforo, M. Pfützner, S. Pietri, Zs. Podolyák, A. Prochazka, W. Prokopowicz, F. Recchia, P.H. Regan, M.W. Reed, D. Rudolph, E. Sahin, H. Schaffner, A. Sharma, B. Sitar, D. Siwal, K. Steiger, P. Strmen, T.P.D. Swan, I. Szarka, C.A. Ur, P.M. Walker, H. Weick, O. Wieland, and H-J. Wollersheim Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro, 35020, Italy Dipartimento di Fisica e Astronomia dell’Università degli Studi di Padova, Padova, 35131, Italy Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano, 20133, Italy Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova, 35131, Italy Instituto de F́ısica Corpuscular, CSIC-Universitat de València, València, E-46980, Spain Department of Physics, University of Surrey, Guildford, GU2 7XH, United Kingdom Universidade de Santiago de Compostela, Santiago de Compostela, E-175706, Spain GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, D-64291, Germany Dipartimento di Fisica dell’Università degli Studi di Milano, Milano, 20133, Italy School of Computing, Engineering and Mathematics, University of Brighton, Brighton, BN2 4GJ, United Kingdom EEI, Universidade de Vigo, Vigo, E-36310, Spain Grupo de F́ısica Nuclear, Universidad de Salamanca, Salamanca, E-37008, Spain Physik Department, Technische Universität München, Garching, D-85748, Germany Niewodniczanski Institute of Nuclear Physics, Polish Academy of Science, Krakow, PL-31-342, Poland Department of Physics, Lund University, Lund, S-22100, Sweden Faculty of Mathematics and Physics, Comenius University, Bratislava, 84215, Slovakia Department of Physics and Astrophysics, University of Delhi, Delhi, 110007, India Institut für Kernphysik, Universität zu Köln, Köln, D-50937, Germany Faculty of Physics, University of Warsaw, Warsaw, PL-00681, Poland (Dated: April 24, 2014)

The structure of the neutron-rich bismuth isotope Bi-217 has been studied for the first time. The fragmentation of a primary U-238 beam at the FRS-RISING setup at GSI was exploited to perform gamma-decay spectroscopy, since mu s isomeric states were expected in this nucleus. Gamma rays following the decay of a t(1/2) = 3 mu s isomer were observed, allowing one to establish the low-lying structure of Bi-217. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.

The region of neutron-rich nuclei beyond 208Pb has been very difficult to explore due to its high mass and exoticity. However, recent experimental improvements allowed one to perform a quite extended isomer decay spectroscopy of these nuclei.

Neutron-rich nuclei in the lead region, beyond N=126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in 210Hg: the 8+ isomer expected from the seniority scheme in the νg9/2 shell and a second one at low spin and low excitation energy. The decay strength of the 8+ isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3− state, although this is in contrast with theoretical expectations.

The population of 102Zr following the β decay of 102Y produced in the projectile fission of 238U at the GSI facility in Darmstadt, Germany has been studied. 102Y is known to ß decay into 102Zr via two states, one of high spin and the other low spin. These states preferentially populate different levels in the 102Zr daughter. In this paper the intensities of transitions in 102Zr observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Jülich.

Evidence has been obtained for the existence of the long predicted 16+ spin-gap isomer in 96Cd. The decay of the isomer was identified and studied following the use of an 850 MeV/u beam of 124Xe impinging on a Be target and the fragment recoil separator at the GSI Laboratory. Gamma decays from the fragments were detected using the RISING gamma ray array, in its stopped beam configuration, plus a silicon active stopper. The data obtained have been compared with shell model predictions, which indicate that the isoscalar neutron-proton interaction plays a key role in the formation of the isomer.

The knowledge of excited states in the odd-odd Pm-150, completely unknown until recently, is important both for understanding double beta decay of Nd-150 and for nuclear structure studies in mass regions with a quantum phase transition. A large number of excited states have been determined for the first time in this nucleus by measuring spectra of the Sm-152(d,alpha) direct reaction at 25 MeV with the Munich Q3D spectrograph and by gamma-ray spectroscopy with the (p, n gamma) reaction at 7.1 MeV at the Bucharest tandem accelerator. Some of these levels correspond to peaks recently observed with the (He-3,t) reaction at 140 MeV/u.

Results are presented from a one-neutron knockout experiment at relativistic energies of \( \approx 420 A\) MeV on 51-55Sc using the GSI Fragment Separator as a two-stage magnetic spectrometer and the MINIBALL array for gamma-ray detection. Inclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the contributions corresponding to knockout from the \( \nu p_{1/2}\) , \( \nu p_{3/2}\) , (L = 1 and \( \nu f_{7/2}\) , \( \nu f_{5/2}\) (L = 3 neutron orbitals. The observed L = 1 and L = 3 contributions are compared with theoretical cross-sections using eikonal knockout theory and spectroscopic factors from shell model calculations using the GXPF1A interaction. The measured inclusive knockout cross-sections generally follow the trends expected theoretically and given by the spectroscopic strength predicted from the shell model calculations. However, the deduced L = 1 cross-sections are generally 30-40% higher while the L = 3 contributions are about a factor of two smaller than predicted. This points to a promotion of neutrons from the \( \nu f_{7/2}\) to the \( \nu p_{3/2}\) orbital indicating a weakening of the N = 28 shell gap in these nuclei. While this is not predicted for the phenomenological GXPF1A interaction such a weakening is predicted by recent calculations using realistic low-momentum interactions \( V_{low k}\) obtained by evolving a chiral N3LO nucleon-nucleon potential.

Neutron-rich isotopes around lead, beyond N=126, have been studied exploiting the fragmentation of an uranium primary beam at the FRS-RISING setup at GSI. For the first time β-decay half-lives of Bi219 and Tl211,212,213 isotopes have been derived. The half-lives have been extracted using a numerical simulation developed for experiments in high-background conditions. Comparison with state of the art models used in r-process calculations is given, showing a systematic underestimation of the experimental values, at variance from close-lying nuclei.

The population of 102Zr following the β decay of 102Y produced in the projectile fission of 238U at the GSI facility in Darmstadt, Germany has been studied. 102Y is known to ß decay into 102Zr via two states, one of high spin and the other low spin. These states preferentially populate different levels in the 102Zr daughter. In this paper the intensities of transitions in 102Zr observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Jülich.

The population of Zr-102 following the beta decay of Y-102 produced in the projectile fission of U-238 at the GSI facility in Darmstadt, Germany has been studied. Y-102 is known to beta decay into Zr-102 via two states, one of high spin and the other low spin. These states preferentially populate different levels in the Zr-102 daughter. In this paper the intensities of transitions in Zr-102 observed are compared with those from the decay of the low-spin level studied at the TRISTAN facility at Brookhaven National Laboratory and of the high-spin level studied at the JOSEF separator at the Kernforschungsanlage Julich.

The neutron-rich lead isotopes, up to (216)Pb, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond (208)Pb.

One-neutron knockout reactions in a 9 Be target have been investigated at relativistic energies, near 700 MeV/ u , for a set of sd -shell, neutron-rich nuclei. The experiment was performed in the FRS spectrometer, at GSI. γ -ray measurements were carried out by means of the MINIBALL γ -ray spectrometer and allowed the determination of partial cross-sections and branching ratios corresponding to the final states of the emerging knockout fragments. Experimental results are presented for 17 C, 19 N, 21 O and 25 F projectiles. The role of excited states of the N − 1 fragments in the composition of the ground state of these neutron-rich projectiles is outlined in this work.

Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a 238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structure of neutron-rich nuclei around the Z=82 shell closure. Some preliminary results are reported in this paper.

Boutachkov, P.; Gorska, M.; Grawe, H.; Blazhev, A.; Braun, N.; Brock, T. S.; Liu, Z.; Singh, B. S. Nara; Wadsworth, R.; Pietri, S.; Domingo-Pardo, C.; Kojouharov, I.; Caceres, L.; Engert, T.; Farinon, F.; Gerl, J.; Goel, N.; Grbosz, J.; Hoischen, Robert; Kurz, N.; Nociforo, C.; Prochazka, A.; Schaffner, H.; Steer, S. J.; Weick, H.; Wollersheim, H. -J.; Faestermann, T.; Podolyak, Zs.; Rudolph, Dirk; Atac, A.; Bettermann, L.; Eppinger, K.; Finke, F.; Geibel, K.; Gottardo, A.; Hinke, C.; Ilie, G.; Iwasaki, H.; Jolie, J.; Kruecken, R.; Merchan, E.; Nyberg, J.; Pfuetzner, M.; Regan, P. H.; Reiter, P.; Rinta-Antila, S.; Scholl, C.; Soderstrom, P. -A.; Warr, N.; Woods, P. J.

One-neutron knockout data for N18-22 are analyzed in the eikonal approximation of the Glauber model. The role of the s-d shell and the crossing of the N = 14 neutron subshell are discussed. Of particular interest is the nucleus N-22, where the knockout data provide a sensitive experimental test for a possible halo structure of its ground state. The observation of a narrow momentum distribution of the N-21 fragments, together with an essential 1s(1/2) contribution needed to describe the observed longitudinal-momentum distribution, allow the firm conclusion that the ground state of N-22 is a well-developed nuclear halo. The results also show that the N = 14 subshell in N-22 is somewhat reduced as compared to that of O-23.

The RISING setup at the GSI-FRS facility was used to investigate the isomer and beta decays in N similar to Z similar to 50 Cd, Ag and Pd isotopes. A preliminary analysis of the data has revealed new results on the T-z=1, Pd-94, Ag-96 and Cd-98 isotopes. In Pd-94 a new high-spin isomer was observed, whilst in Ag-96 3 new isomeric states were identified, including core-excited states. In Cd-98 a new high-energy isomeric gamma-ray transition is observed, thus enabling us to confirm the previous spin assignment for the core-excited 12(+) isomer.