On the origin of the anomalous behaviour of 2+ excitation energies in the neutron-rich Cd isotopes

Recent experimental results obtained using $\beta$ decay and isomer spectroscopy indicate an unusual behaviour of the energies of the first excited 2$^{+}$ states in neutron-rich Cd isotopes approaching the N=82 shell closure. To explain the unexpected trend, changes of the nuclear structure far-off stability have been suggested, namely a quenching of the N=82 shell gap already in $^{130}$Cd, only two proton holes away from doubly magic $^{132}$Sn. We study the behaviour of the 2$^+$ energies in the Cd isotopes from N=50 to N=82, i.e. across the entire span of a major neutron shell using modern beyond mean field techniques and the Gogny force. We demonstrate that the observed low 2$^+$ excitation energy in $^{128}$Cd close to the N=82 shell closure is a consequence of the doubly magic character of this nucleus for oblate deformation favoring thereby prolate configurations rather than spherical ones.Comment: 10 pages, 4 figures, to be publised in Phys. Lett.

Low-energy nuclear excitations along the α-decay chains of superheavy 292Lv and 294Og

We present the first triaxial beyond-mean-field study of the excitation spectra of even-even superheavy nuclei. As representative examples, we have chosen the members of the α-decay chains of 292Lv and 294Og, the heaviest even-even nuclei which have been synthesized so far using 48Ca-induced fusion-evaporation reactions. In our calculations, the effective finite-range density-dependent Gogny force is used and the angular-momentum and particle-number symmetries are restored. Configuration-mixing calculations are performed to determine ground- and excited-state deformations and to establish the collective band structures of these nuclei. Rapidly varying characteristics are predicted for the members of both decay chains, which are further accentuated when compared to the predictions of simple collective models. Based on the present calculations, the prospect of observing α-decay fine structures in future experiments is discusse

High-spin structure in K-40

High-spin states of K-40 have been populated in the fusion-evaporation reaction C-12(Si-30,np)K-40 and studied by means of gamma-ray spectroscopy techniques using one triple-cluster detector of the Advanced Gamma Tracking Array at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. Several states with excitation energy up to 8 MeV and spin up to 10(-) have been discovered. These states are discussed in terms of J = 3 and T = 0 neutron-proton hole pairs. Shell-model calculations in a large model space have shown good agreement with the experimental data for most of the energy levels. The evolution of the structure of this nucleus is here studied as a function of excitation energy and angular momentum. ©2012 American Physical SocietyWe would like to thank the Swedish National Infrastructure for Computing (SNIC) and the Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) for the computer resources used in parts of the analysis.This work was financed by EURONS AGATA (Contract no. 506065-R113), the Swedish Research Council under contracts 621-2008-4163, 621-2011-4522, 822-2005-3332 and 821-2010-6024, the Japan Society for the Promotion of Science (JSPS) Kakenhi Grant No. 23·01752, Ankara University (BAP Project number 05B4240002), the Polish Ministry of Science and Higher Education under grants number DPN/N190/AGATA/2009 and N N202 073935, the German BMBF under Grants 06K-167, 06KY205I and 06KY9136I, the Knut and Alice Wallenberg Foundation contract number 2005.0184 and STFC (UK). A. Gadea and E. Farnea acknowledge the support of MICINN, Spain, and INFN, Italy through the AIC-D-2011-0746 bilateral action. A. Gadea’s activity has been partially supported by the Generalitat Valenciana, Spain, under grant PROMETEO/2010/101. A. Gadea, A. Jungclaus, A. Poves and B. Quintana acknowledge support from the MICINN, Spain, under grant FPA2011-29854. A. Pove is partially supported by the Comunidad de Madrid (Spain) (HEPHACOS S2009-ESP-1473). G. Jaworski acknowledges the support of the Center for Advanced Studies of Warsaw University of Technology. B. Cederwall acknowledge the support of the Göran Gustafsson FoundationPeer Reviewe

Analysis and results of the 104Sn Coulomb excitation experiment

G. Guastalla, et al. XX International School on Nuclear Physics, Neutron Physics and Applications (Varna 2013); 5 pags.; 1 fig.The analysis of the Coulomb excitation experiment conducted on 104Sn required a strict selection of the data in order to reduce the large background present in the γ-ray energy spectra and identify the γ-ray peak corresponding to the Coulomb excitation events. As a result the B(E2; 0+ →2+) value could be extracted, which established the downward trend towards 100Sn and therefore the robustness of the N=Z=50 core against quadrupole excitations. Published under licence by IOP Publishing LtdA. J. would like to thank the Spanish Ministerio de Ciencia e Innovacion for financial support under Contract No. FPA2011-29854- C04Peer Reviewe

Low-velocity transient-field technique with radioactive ion beams: G factor of the first excited 2 + state in 72Zn

A. Illana et al. ; 11 pags. ; 10 figs. ; 3 tabs. ; PACS number(s): 23.20.En, 21.10.Ky, 21.60.Cs, 27.50.+eThe g factor of the first excited 2+ state in 72Zn has been measured using the transient-field (TF) technique in combination with Coulomb excitation in inverse kinematics. This experiment presents only the third successful application of the TF method to a short-lived radioactive beam in 10 y, highlighting the intricacies of applying this technique to present and future isotope separator on-line facilities. The significance of the experimental result, g(21+)=+0.47(14), for establishing the structure of the Zn isotopes near N=40 is discussed on the basis of shell-model and beyond-mean-field calculations, the latter accounting for the triaxial degree of freedom, configuration mixing, and particle number and angular momentum projections. © 2014 American Physical Society.This work has been supported by the Spanish Ministerio de Ciencia e Innovacion under Contracts No. FPA2009-13377- ´ C02 and No. FPA2011-29854-C04 and the Spanish Project MEC Consolider-Ingenio 2010, Project No. CDS2007-00042.Peer Reviewe

Light and heavy transfer products in Xe 136 + U 238 multinucleon transfer reactions

A. Vogt et al.; 12 pags.; 14 figs.; PACS number(s): 24.10.−i, 25.70.Hi, 29.30.Aj, 29.40.Gx© 2015 American Physical Society. ©2015 American Physical Society. Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in Xe136+U238 have been measured in a high-resolution γ-ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the grazing model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z=93 is found to perform nuclear structure investigations. In-beam γ-ray spectroscopy is feasible for few-neutron transfer channels in U and the -2p channel populating Th isotopes.The research leading to these results has received funding from the German Bundesministerium fur Bildung ¨ und Forschung (BMBF) under Contract No. 05P12PKFNE TP4, the European Union Seventh Framework Programme (FP7/2007-2013) under Grant No. 262010-ENSAR, and the Spanish Ministerio de Ciencia e Innovacion under Contract ´ No. FPA2011-29854-C04. A.V. thanks the Bonn-Cologne Graduate School of Physics and Astronomy (BCGS) for financial support. One of the authors (A. Gadea) was supported by MINECO, Spain, under Grants No. FPA2011-29854-C04 and No. FPA2014-57196-C5, Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019, and EU under the FEDER program.Peer Reviewe

Particle-core coupling in S 37

R. Chapman et al. ; 8 págs.; 6 figs.; 2 tabs.Excited states of the neutron-rich N=21 S37 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. The level scheme of S37 was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11/2-) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1f7/2 neutron to the first 2+ state of the S36 core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed. ©2016 American Physical SocietyWe would like to thank the technical staff of the INFN Legnaro National Laboratory for their support during this experiment. This work was supported by the EPSRC (U.K). Four of us (A.H,M.B, K.L.K., and A.P.) would like to acknowledge the receipt of financial support from EPSRC during the course of this work. A.J. would like to acknowledge support from the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5-4-P. Z.D. acknowledges financial support from OTKA Grant No. K100835.Peer Reviewe

Pair neutron transfer in Ni 60 + Sn 116 probed via γ -particle coincidences

D. Montanari et al. ; 6 págs.; 5 figs.; 1 tab.We performed a γ-particle coincidence experiment for the Ni60+Sn116 system to investigate whether the population of the two-neutron pickup channel leading to Ni62 is mainly concentrated in the ground-state transition, as has been found in a previous work [D. Montanari et al., Phys. Rev. Lett. 113, 052501 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.052501]. The experiment has been performed by employing the PRISMA magnetic spectrometer coupled to the Advanced Gamma Tracking Array (AGATA) demonstrator. The strength distribution of excited states corresponding to the inelastic, one- and two-neutron transfer channels has been extracted. We found that in the two-neutron transfer channel the strength to excited states corresponds to a fraction (less than 24%) of the total, consistent with the previously obtained results that the 2n channel is dominated by the ground-state to ground-state transition. ©2016 American Physical SocietyThis work was partly supported by the EU FP7/2007-2013 under Grant No. 262010-ENSAR and by the Croatian Science Foundation under Project No. 7194. A.G. was partially supported by MINECO and Generalitat Valenciana, Spain, under Grants No. FPA2014-57196-C5 and No. PROMETEOII/2014/019 and the EU under the FEDER program.Peer Reviewe

β decay of semi-magic 130Cd: Revision and extension of the level scheme of 130 In

A. Jungclaus et al.; 8 págs.; 5 figs.; 3 tabs.The β decay of the semi-magic nucleus Cd130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In130 and the observation of additional β feeding to high-lying core-excited states in In130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N=50-82 neutron and Z=28-50 proton shells and the NA-14 interaction, and good agreement is found. ©2016 American Physical SocietyWe thank the staff of the RIKEN Nishina Center accelerator complex for providing stable beams with high intensities to the experiment. We acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. This work was supported by the Spanish Ministerio de Ciencia e Innovación under contract FPA2011-29854-C04 and the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5- 4-P, the Generalitat Valenciana (Spain) under Grant No. PROMETEO/2010/101, the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (NRF-2014S1A2A2028636, 2016K1A3A7A09005579), the Priority Centers Research Program in Korea (2009-0093817), OTKA Contract No. K-100835, JSPS KAKENHI (Grant No. 25247045), the European Commission through the Marie Curie Actions call FP7-PEOPLE-2011-IEF under Contract No. 300096, the US Department of Energy, Office of Nuclear Physics, under Contract No.DE-AC02-06CH11357, the STFC (UK), the “RIKEN foreign research program,” the German BMBF (No. 05P12RDCIA, No. 05P12RDNUP, and No. 05P12PKFNE), HIC for FAIR, the DFG cluster of excellence “Origin and Structure of the Universe,” and DFG (Contract No. KR2326/2-1).Peer Reviewe