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Wobbling motion as an exotic collective mode in nuclei without axial symmetry, was intensively discussed during the last few years. The observation of the newly proposed transverse wobbling, first reported in $^{135}$Pr and soon after in nuclei from other mass regions, was considered as a significant discovery in low-spin nuclear structure. However, both the reported experimental results and the proposed theoretical models were lively questioned in a series of works devoted to the investigation of the low-spin wobbling mode in the same nucleus. The electromagnetic properties of the $\Delta I=1$ transitions connecting the one- to zero-phonon and the two- to one-phonon wobbling bands in $^{135}$Pr were recently remeasured, demonstrating their predominant $M1$ magnetic character which is in contradiction with the wobbling motion interpretation. These new experimental observables being well reproduced by both quasiparticle-plus-triaxial-rotor model and interacting boson-fermion model calculations, are against the previously proposed wobbling characteristics of the low-spin bands in $^{135}$Pr. On the other hand, we obtained conclusive experimental evidence for the theoretically suggested transverse wobbling bands at medium spin in $^{136}$Nd. The comparison of the experimental data with calculations utilizing the triaxial projected shell model and a new developed particle-rotor model with frozen orthogonal geometry of the active nucleons, supports the description in terms of transverse wobbling of medium-spin bands in triaxial even-even nuclei.

Physics letters / B 762, 404 - 408 (2016). doi:10.1016/j.physletb.2016.09.058, Published by North-Holland Publ., Amsterdam

A big part in understanding the nucleosynthesis of heavy nuclei is a proper description of the effective interaction between an α-particle and a target nucleus. Information about the so-called α + nucleus optical-model potential is achieved by precise cross-section measurements at sub-Coulomb energies aiming to constrain the theoretical models for the nuclear physics input-parameters. The cross sections of the 108Cd( α , γ ) and 108Cd( α , n ) reaction have been measured for the first time close to the astrophysically relevant energy region via the in-beam method at the high-efficiency γ-ray spectrometer HORUS and via the activation technique at the Cologne Clover Counting Setup at the Institute for Nuclear Physics in Cologne, Germany. Comparisons between experimental results and theoretical predictions calculated in the scope of the Hauser–Feshbach statistical model confirm the need for a exponentially decreasing imaginary part of the potential. Moreover, it is shown that the results presented here together with already published data indicate that a systematic investigation of the real part of the potential could help to further improve the understanding of reactions involving α-particles.

Although environmental radioactivity is all around us, the collective public imagination often associates a negative feeling to this natural phenomenon. To increase the familiarity with this phenomenon we have designed, implemented, and tested an interdisciplinary educational activity for pre-collegiate students in which nuclear engineering and computer science are ancillary to the comprehension of basic physics concepts. Teaching and training experiences are performed by using a 4&rdquo, &times, 4&rdquo, NaI(Tl) detector for in-situ and laboratory &gamma, ray spectroscopy measurements. Students are asked to directly assemble the experimental setup and to manage the data-taking with a dedicated Android app, which exploits a client-server system that is based on the Bluetooth communication protocol. The acquired &gamma, ray spectra and the experimental results are analyzed using a multiple-platform software environment and they are finally shared on an open access Web-GIS service. These all-round activities combining theoretical background, hands-on setup operations, data analysis, and critical synthesis of the results were demonstrated to be effective in increasing students&rsquo, awareness in quantitatively investigating environmental radioactivity. Supporting information to the basic physics concepts provided in this article can be found at http://www.fe.infn.it/radioactivity/educational.

Undergraduate students at the University of Dallas have investigated basic properties of nuclei through γ-ray and neutron spectroscopy following neutron scattering. The former has been used primarily for nuclear structure investigations, while the latter has been used to measure neutron scattering cross sections important for fission reactor applications. A series of ( n , n ’) and ( n , n ’γ) measurements have been made on 54 Fe and 56 Fe to determine neutron cross sections for scattering to excited levels in these nuclei. The former provides the cross sections directly and the latter are used to deduce inelastic neutron scattering cross sections by measuring the γ-ray production cross sections to states not easily resolved in neutron spectroscopy. All measurements have been completed at the University of Kentucky Accelerator Laboratory using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. Students participate in accelerator operation, experimental setup, data acquisition, and data analyses. An overview of the research program and student contributions is presented.

Our understanding of the evolution of the shell structure in nuclei far from stability is based on the study of some key nuclei. Nuclei at or next to double shell closures play a special role in this. Presently, a lot of discussion is concentrated on the neutron-rich calcium isotopes, which provide a rich testing ground for various nuclear models with several traditional and new magic numbers. 60 Ca is now almost within reach with the most advanced radioactive beam facilities. In order to investigate the evolution of the shell gap at N = 40, the configuration of states in the odd–even titanium isotopes up to N = 37 ( 59 Ti) have been studied. In order to experimentally access the shell gap at N = 40, it is nowadays within the reach of the most advanced facility the investigation of neutron hole configuration states in odd–even titanium isotopes up to N = 37, in the 59 Ti nucleus. Such states correspond to relatively simple configurations that constitute a challenging testing ground for effective nuclear interactions. The new data obtained in our experiment allows to place the present predictions concerning the shell closure at N = 40 in the calcium region on a more solid ground.

Lifetimes of high-spin states in 69As have been measured using Doppler shift attenuation technique with the GASP and RFD setup. The determined transition probabilities indicate large deformation associated with some rotational bands in this nucleus.