Nucleus Nucleus 2015

Dynamical Dipole Mode in the 40,48Ca+152,144Sm fusion-evaporation and fission reactions at 11 MeV/nucleon

23 Jun 2015, 15:15

20m

Aula A (Dipartimento di Fisica ed Astronomia, Università di Catania)

Oral presentation Fusion and Fission Fusion and Fission

Speakers

Dr Concetta Parascandolo (INFN - Napoli, Italy)Dr Dimitra Pierroutsakou (INFN - Napoli, Italy)

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The Dynamical Dipole mode (DD) is a large amplitude collective oscillation of protons against neutrons of the dinucleus formed in charge asymmetric heavy-ion collisions [1-4]. The study of its gamma decay gives us
valuable information on the reaction dynamics and could shed light on the density dependence of the symmetry energy in the nuclear matter Equation of State at sub-saturation densities [5]. Furthermore, being a pre-equilibrium phenomenon, the DD  decay could be an interesting cooling mechanism of the
composite system in the fusion path, to facilitate super-heavy element formation. In this framework, we investigated the DD excitation and subsequent gamma decay in the mass region of the 192Pb composite system
formed in the fusion-evaporation and fission 40Ca + 152Sm and 48Ca +144Sm reactions at Elab = 440 MeV and 485 MeV, respectively. The experiment was performed at Laboratori Nazionali del Sud, Italy. The gamma-rays
and the light charged particles emitted in the reaction were detected by using the MEDEA apparatus [6] while the heavy reaction fragments were detected by position sensitive Parallel Plate Avalanche Counters
placed symmetrically around the beam direction. The analysis of the gamma-ray spectra and angular distributions evidenced in a model independent way the DD excitation in such a heavy composite system in both exit channels: fusion-evaporation and fission. The possible implications of observing DD gamma radiation in the evaporation channel of a heavy composite system in the super-heavy element quest will be discussed. On the other hand, the observation of DD gamma radiation also in the fission exit channel (never observed before) provides inedited information on the DD excitation at higher partial waves, setting thus new severe constraints on theoretical models.

[1] S. Flibotte et al., PRC77 (1996)1448
[2] F. Amorini et al., PRC69 (2004) 014608
[3] D. Pierroutsakou et al., PRC71 (2005)054605, PRC80(2009)024612, B. Martin et al., PLB664 (2008)47
[4] A. Corsi et al., PLB679 (2008)197, A. Giaz PRC90 (2014) 014609
[5] V. Baran et al., PRC79 (2009)021603(R)
[6] E. Migneco et al., NIMA314 (1992)31