Advances in Radioactive Isotope Science

Study on the Isoscalar Excitation of the Pygmy Dipole Resonance in 68Ni

1 Jun 2017, 18:05

15m

Quandry Peak

Invited Presentation Breakout 2

Speaker

Nunzia Simona Martorana (LNS-INFN, Catania, Italy)

Description

N.S. Martorana, L. Acosta, M.V. Andrés, G. Cardella, F. Catara, E. De Filippo, S. De Luca, D. Dell'Aquila, B. Gnoffo, E.G. Lanza, G. Lanzalone, I. Lombardo, C. Maiolino, S. Norella, A. Pagano, E.V. Pagano, M. Papa, S. Pirrone, G. Politi, F. Porto, L. Quattrocchi, F. Rizzo, P. Russotto, A. Trifirò, M. Trimarchi, M. Vigilante, A. Vitturi Recently, much relevance has been given to the collective states in neutron-rich nuclei. The remarkable interest in these states is driven by the presence of an electric dipole response around the nucleon binding energy [1,2]. This mode, the so called Pygmy Dipole Resonance (PDR), although is carrying few per cent of the isovector Energy Weighted Sum Rule (EWSR) has a strong relation with the symmetry energy and it has been used as a further tool to constrain it. It is predicted to be present in almost all nuclei with neutron excess: in particular for nuclei far from the stability line. This mode can be populated by both isoscalar and isovector probes due to the properties of its transition densities [3]. Several experiments, with both the probes, have been performed on stable nuclei [1,2,4,5]. Whereas, the study of the PDR with unstable nuclei has been done in pioneering experiments carried out at the GSI, using relativistic Coulomb excitations on 132Sn [6] and 68Ni [7] isotopes. We use, for the first time, an isoscalar probe to excite the PDR on an unstable isotope. The experiment with a 68Ni beam at 33 MeV/nucleon on a 12C target was performed at LNS-INFN of Catania. The unstable beam was produced by In Flight Fragmentation method in a dedicated In Fligth Radioactive Ion Beams (FRIBs) transport line. The detector systems CHIMERA [8] and Farcos [9] were used to detect both gamma and charged products. References: [1] D. Savran, T. Aumann and A. Zilges, Prog. Part. Nucl. Phys. 70, 210 (2013). [2] A. Bracco, F.C. L. Crespi, and E. G. Lanza, Eur. Phys. J. A 51 (2015). [3] E. G. Lanza, A. Vitturi, M. V. Andrés, F. Catara and D. Gambacurta, Phys. Rev. C 84, 064602 (2011). [4] D. Savran et al, Phys. Rev. Lett. 100, 232501 (2008). [5] J. Endres et al, Phys. Rev. C 80, 034302 (2009). [6] P. Adrich et al, Phys. Rev. Lett. 95, 132501 (2005). [7] O. Wieland et al, Phys. Rev. Lett. 102, 092502 (2009). [8] A.Pagano et al Nucl. Phys. A 734 (2004) 504. [9] E.V. Pagano et al, EPJ Web of Conferences 117, 10008 (2016).