Dipole strength measurements in the 132Sn region
نویسندگان
چکیده
Properties of the Giant Dipole Resonance in nuclei far off stability provide information on the isospin dependence of the effective nuclear interaction [1]. Moreover, recent RPA calculations of the dipole strenght in n-rich nuclei predict the existence of a new mode of collective excitation, exhausting a considerable fraction of the sum rule strenght [2, 3]. This so called Pygmy resonance, expected at energies close to the neutron separation threshold, is most commonly explained as a collective oscillation of a neutron skin against the core of a nucleus. There are, however, numerous controversies on the nature of this excitation as well as on the degree of its collectivity. Nevertheless, the existence of such a low lying state would have pronounced consequences for the astrophysical r-process scenarios [4]. Measurements of the dipole strength functions in neutron-rich nuclei around the doubly magic nucleus Sn have been performed with the LAND-FRS facility at GSI.
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