C. Rizzo

Dynamical dipole mode in fusion reactions with exotic nuclear beams

We report the properties of the prompt dipole radiation, produced via a collective bremsstrahlung mechanism, in fusion reactions with exotic beams. We show that the

Prompt dipole radiation in fusion reactions

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THE DYNAMICAL DIPOLE RADIATION IN DISSIPATIVE COLLISIONS WITH EXOTIC BEAMS

yield is sensitive to the density dependence of the symmetry energy below/around saturation. Moreover, we find that the angular distribution of the emitted photons from such fast collective mode can represent a sensitive probe of its excitation mechanism and of fusion dynamics in the entrance channel.

Exotic break-up modes in heavy ion reactions at low energies

Abstract The prompt γ-ray emission is investigated in the 16 A MeV energy region by means of the 36,40Ar + 96,92Zr fusion reactions leading to a compound nucleus in the vicinity of 132Ce. The dynamical nature of this radiation is confirmed. We show that the prompt γ radiation has an angular distribution pattern consistent with a dipole oscillation along the symmetry axis of the dinuclear system. The data are compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics.

Pre-equilibrium GDR in a heavy composite system

Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this work we present a selection of reaction observables in dissipative collisions particularly sensitive to the isovector part of the interaction, i.e. to the symmetry term of the nuclear Equation of State (EoS). At low energies the behavior of the symmetry energy around saturation influences dissipation and fragment production mechanisms. We will first discuss the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation during the charge equilibration in fusion and deep-inelastic collisions. We will review in detail all the main properties, yield, spectrum, damping and angular distributions, revealing important isospin effects. Reactions induced by unstable 132Sn beams appear to be very promising tools to test the sub-saturation Isovector EoS. Predictions are also presented for deep-inelastic and fragmentation collisions induced by neutron ...

Dynamical Dipole mode in heavy-ion fusion reactions in the 192Pb mass region

New reaction mechanisms occurring in heavy ion collisions at low energy (10- 30 MeV/A) are investigated within the Stochastic Mean Field model. We concentrate on the analysis of ternary breakup events, of dynamical origin, occurring in semi-central reactions, where the formation of excited systems in various conditions of shape and angular momentum is observed. We show how this fragmentation mode, which can be considered as a precursor of the neck emission observed at higher beam energies, emerges from the combined action of surface (neck) instabilities and angular momentum effects. Interesting perspectives are opening towards the investigation of this mechanism in neutron-rich (or exotic) systems, with the possibility to access information on the low-density behavior of the nuclear symmetry energy.

Low Energy Reaction Mechanisms In a Transport Approach

The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first time in the formation of a heavy composite system in the A~190 mass region, in fusion-evaporation and fission events. The composite system was formed at identical conditions of excitation energy and spin from two reactions with different charge asymmetry: the charge asymmetric 40Ca + 152Sm and the nearly charge symmetric 48Ca + 144Sm at E lab =11 and 10.1 MeV/nucleon, respectively. In this paper, we report the results on fusion evaporation events and the preliminary analysis on fission channel.

DYNAMICAL DIPOLE MODE IN FUSION HEAVY-ION REACTIONS IN THE MASS REGION OF A = 192

The dynamical dipole mode was investigated in the mass region of the 192Pb compound nucleus, by using the 40Ca + 152Sm and 48Ca + 144Sm reactions at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

Exploring the nuclear matter phase diagram with heavy ion reactions

Starting from Heavy Ion Collisions with exotic nuclear beams at low energy, the reaction path is investigated in a transport theory based on a stochastic mean field approach. We focus on the interplay between reaction mechanisms, fusion vs. break-up in HIC with exotic nuclear beams at low energies. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10AMeV are evaluated looking at the evolution of the phase-space quadrupole collective modes. The break-up events appear sensitive to the stiffness of the symmetry energy. 197Au + 197Au collisions at 15 and 23 AMeV are simulated to investigate the main modes of re-separation, ternary-quaternary partition, of a heavy nuclear system.

Measurements of dynamical dipole in isospin asymmetric fusion reactions

C. PARASCANDOLO, D. PIERROUTSAKOU, C. AGODI, R. ALBA, V. BARAN, A. BOIANO, M. COLONNA, R. CONIGLIONE, E. DE FILIPPO, A. DEL ZOPPO, M. DI TORO, U. EMANUELE, F. FARINON, A. GUGLIELMETTI , M. LA COMMARA, C. MAIOLINO, B. MARTIN, M. MAZZOCCO, C. MAZZOCCHI , C. RIZZO, M. ROMOLI, D. SANTONOCITO, C. SIGNORINI, R. SILVESTRI, F. SORAMEL, E. STRANO, D. TORRESI, A. TRIFIRO AND M. TRIMARCHI a Dip. di Fisica e Astronomia, Universita di Padova and INFN, Sezione di Padova,