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HK: Fachverband Hadronen und Kerne

HK 71: Nuclear Structure and Dynamics I

HK 71.1: Eingeladener Gruppenbericht

Donnerstag, 19. März 2009, 16:30–17:00, H-ZO 40

The GDR strength function in exotic nuclei measured with gamma decay — •Angela Bracco — Università di Milano e INFN sez. Milano

The study of the gamma decay from the giant dipole resonance (GDR) in nuclei far from stability both at zero and finite temperature is a powerful tool to obtain information on the nuclear properties, such as shape and isospin effects. In particular, two specific problems related to isospin effects will be discussed.

The first problem is that of the possible restoration of the isospin symmetry at finite temperature. The problem of determining isospin mixing in N=Z nuclei has been addressed both at zero and finite temperature T up to Z=N=32 (with the mixing found to increase with Z). In addition at T=2 and T=0 the isospin mixing are similar. Thus the combination of data at T=0 and T>0 provide important information on this problem. A new exclusive experiment on the GDR at T= 2 MeV in the unexplored region N=Z=40 was made using the GARFIELD-HECTOR set up at LNL. Preliminary results will be presented.

The second topic that will be discussed is the search of the pygmy resonance in the exotic 68Ni nucleus using Coulomb excitation at 600 A MeV and the RISING array at the FRS of GSI. The gamma decay of 68Ni isotopes was measured in BaF2 and HpGe detectors. A peak at approximately 11 MeV was observed. This is the first measurement of the gamma decay of the Pygmy Resonance with radioactive beams. Discussion will be made on the interest in relating these states with the oscillation of the neutron skin.