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Crespi F.C.L.,Polytechnic of Milan | Crespi F.C.L.,National Institute of Nuclear Physics, Italy | Bracco A.,Polytechnic of Milan | Bracco A.,National Institute of Nuclear Physics, Italy | And 79 more authors.
Physical Review Letters | Year: 2014

The properties of pygmy dipole states in Pb208 were investigated using the Pb208(O17, O17'γ) reaction at 340 MeV and measuring the γ decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted γ rays and of the scattered particles were measured. The results are compared with (γ, γ′) and (p, p′) data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2+ and 3- states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1- excited states from 4 to 8 MeV. © 2014 American Physical Society.


Curien D.,CNRS Hubert Curien Multi-disciplinary Institute | Dudek J.,CNRS Hubert Curien Multi-disciplinary Institute | Molique H.,CNRS Hubert Curien Multi-disciplinary Institute | Sengele L.,CNRS Hubert Curien Multi-disciplinary Institute | And 2 more authors.
International Journal of Modern Physics E | Year: 2011

Following a series of experiments launched by the TetraNuc collaboration to possibly demonstrate the existence of high-rank symmetries in subatomic physics, the first experimental results on the Rare Earth region appear in publications. Meanwhile an important progress has been made on the theory side strongly suggesting that the original criterion of the static tetrahedral symmetry in the form of vanishing quadrupole moments may need to be revised to include explicitly the vibrational motion. The Actinide region seems of particular interest because of the extra stability provided by the octahedral symmetry. In this article a summary of the current experimental efforts on both the Rare-Earth and Actinide regions is given. Finally the ELMA project addressing the experimental search for the symmetries in the Actinides is briefly discussed. © 2011 World Scientific Publishing Company.


Crespi F.C.L.,Polytechnic of Milan | Crespi F.C.L.,National Institute of Nuclear Physics, Italy | Bracco A.,Polytechnic of Milan | Bracco A.,National Institute of Nuclear Physics, Italy | And 70 more authors.
Physical Review C - Nuclear Physics | Year: 2015

2+ and 1- states in Zr90 were populated via the (O17,O′17γ) reaction at 340 MeV. The γ decay was measured with high resolution using the AGATA (advanced γ tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2+,3-, and 1- states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1- state at 6.424 MeV. The comparison of the present (O17,O′17γ) data with existing (γ,γ′) and (p,p′) data in the corresponding region of the γ continuum (6-11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy. © 2015 American Physical Society.


Pellegri L.,University of Milan | Pellegri L.,National Institute of Nuclear Physics, Italy | Bracco A.,University of Milan | Bracco A.,National Institute of Nuclear Physics, Italy | And 53 more authors.
Physical Review C - Nuclear Physics | Year: 2015

A multitude of discrete 2+ states in Sn124 with energy up to 5 MeV were populated and identified with the (O17, O′17γ) reaction at 340 MeV. Cross sections were compared with distorted wave Born approximation predictions and in general a good agreement was found. The measured energy and intensity distributions of the 2+ states are very similar to the predictions based on self-consistent density functional theory and extended QRPA approach accounting for multiphonon degrees of freedom. This provides evidence of the excitation of the pygmy quadrupole resonance in skin nuclei. © 2015 American Physical Society.


Ciemala M.,Niewodniczanski Institute of Nuclear Physics | Kmiecik M.,Niewodniczanski Institute of Nuclear Physics | Maj A.,Niewodniczanski Institute of Nuclear Physics | Kravchuk V.L.,National Institute of Nuclear Physics, Italy | And 4 more authors.
EPJ Web of Conferences | Year: 2014

An experiment focusing on study of the properties of hot rotating compound nucleus of 88Mo was performed in LNL Legnaro using 48Ti beam at energies of 300 and 600 MeV on 40Ca target. The compound nucleus was produced at the temperatures of 3 and 4.5 MeV, with angular momentum distribution with lmax > 60 Latin small letter h with stroke (i.e. exceeding the crtical angular momentum for fission). High-energy gamma rays, measured in coincidence with evaporation residues and alpha particles, were analyzed with the statistical model. The GDR parameters were obtained from the best fit to the data, which allowed investigating an evolution of the GDR width up to high temperatures. © Owned by the authors, published by EDP Sciences, 2014.


Valdre S.,University of Florence | Valdre S.,National Institute of Nuclear Physics, Italy | Barlini S.,University of Florence | Casini G.,National Institute of Nuclear Physics, Italy | And 53 more authors.
EPJ Web of Conferences | Year: 2014

The 48Ti on 40Ca reactions have been studied at 300 and 600 MeV focusing on the fusion-evaporation (FE) and fusion-fission (FF) exit channels. Energy spectra and multiplicities of the emitted light charged particles have been compared to Monte Carlo simulations based on the statistical model. Indeed, in this mass region (A ∼ 100) models predict that shape transitions can occur at high spin values and relatively scarce data exist in the literature about coincidence measurements between evaporation residues and light charged particles. Signals of shape transitions can be found in the variations of the lineshape of high energy gamma rays emitted from the de-excitation of GDR states gated on different region of angular momenta. For this purpose it is important to keep under control the FE and FF processes, to regulate the statistical model parameters and to control the onset of possible pre-equilibrium emissions from 300 to 600 MeV bombarding energy. © Owned by the authors, published by EDP Sciences, 2014.


Sadhukhan J.,University of Tennessee at Knoxville | Sadhukhan J.,Oak Ridge National Laboratory | Mazurek K.,University of Tennessee at Knoxville | Mazurek K.,Oak Ridge National Laboratory | And 13 more authors.
Physical Review C - Nuclear Physics | Year: 2013

The spontaneous fission lifetime of 264Fm has been studied within nuclear density functional theory by minimizing the collective action integral for fission in a two-dimensional quadrupole collective space representing elongation and triaxiality. The collective potential and inertia tensor are obtained self-consistently using the Skyrme energy density functional and density-dependent pairing interaction. The resulting spontaneous fission lifetimes are compared with the static result obtained with the minimum-energy pathway. We show that fission pathways strongly depend on assumptions underlying collective inertia. With the nonperturbative mass parameters, the dynamic fission pathway becomes strongly triaxial and it approaches the static fission valley. On the other hand, when the standard perturbative cranking inertia tensor is used, axial symmetry is restored along the path to fission; an effect that is an artifact of the approximation used. © 2013 American Physical Society.


Vandone V.,University of Milan | Leoni S.,University of Milan | Assanelli D.,University of Milan | Bottoni S.,University of Milan | And 38 more authors.
Journal of Physics: Conference Series | Year: 2012

The transition between order and chaos is studied in the warm rotating nucleus 174W by γ-spectroscopy, focusing on the conservation of selection rules of the K quantum number with the excitation energy, where K is the projection of the total angular momentum on the symmetry axis. The 174W nucleus was populated by the fusion-evaporation reaction of 80Ti (at 217 MeV) on a 128Te backed target. The measurement was performed in July 2010 at Legnaro National Laboratories of INFN using the AGATA Demonstrator HPGe-array coupled to an array of 27 BaF 2 scintillators, named Helena. The data analysis concentrates on γ-γ coincidence matrices selecting the γ-decay flow populating low-K and high-K structures. By a statistical fluctuation analysis the total number of low-K and high-K bands can be evaluated as a function of excitation energy. Comparisons with cranked shell model calculations at finite temperature are used to extract information on the onset of the chaotic regime as a function of excitation energy.


Avdeyev S.P.,Joint Institute for Nuclear Research | Karnaukhov V.A.,Joint Institute for Nuclear Research | Oeschler H.,TU Darmstadt | Kirakosyan V.V.,Joint Institute for Nuclear Research | And 5 more authors.
Bulletin of the Russian Academy of Sciences: Physics | Year: 2010

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d + Au collisions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multi-body Coulomb trajectory calculations under the assumption of various decay times of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emission time is found to be less than 40 fm c-1. © Allerton Press, Inc., 2010.


Mazurek K.,Niewodniczanski Institute of Nuclear Physics | Mazurek K.,French Atomic Energy Commission | Schmitt C.,French Atomic Energy Commission | Wieleczko J.P.,French Atomic Energy Commission | And 2 more authors.
Physical Review C - Nuclear Physics | Year: 2011

The present work is dedicated to a careful investigation of the influence of the potential energy surface on the fission process. The time evolution of nuclei at high excitation energy and angular momentum is studied by means of three-dimensional Langevin calculations performed for two different parametrizations of the macroscopic potential: the Finite Range Liquid Drop Model (FRLDM) and the Lublin-Strasbourg Drop (LSD) prescription. Depending on the mass of the system, the topology of the potential throughout the deformation space of interest in fission is observed to noticeably differ within these two approaches, due to the treatment of curvature effects. When utilized in the dynamical calculation as the driving potential, the FRLDM and LSD models yield similar results in the heavy-mass region, whereas the predictions can be strongly dependent on the Potential Energy Surface (PES) for medium-mass nuclei. In particular, the mass, charge, and total kinetic energy distributions of the fission fragments are found to be narrower with the LSD prescription. The influence of critical model parameters on our findings is carefully investigated. The present study sheds light on the experimental conditions and signatures well suited for constraining the parametrization of the macroscopic potential. Its implication regarding the interpretation of available experimental data is briefly discussed. © 2011 American Physical Society.

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