Production of medium-mass neutron-rich nuclei from fragmentation of 132Sn nuclei

The extension of the nuclear chart towards the neutron-rich side is of utmost importance for nuclear structure and nuclear astrophysics. However, these investigations are limited because of the difficulties in producing neutron-rich nuclei. In the case of masses around A∝130 a two step reaction scheme was proposed to partially overcome this limitation. Therefore, this experimental technique might be a tool for producing beams of extremely neutron-rich isotopes of refractory elements and short lived nuclei in future ISOL facilities. The production cross sections of residual nuclei, were investigated in an experiment performed at the Fragment Separator (GSI). A 950 MeV/u, and 109 particles per spill, 238U beam impinged onto a 650 mg/cm2 Pb target at the entrance of the separator for producing fission fragments. Forward emitted fragments were isotopically identified in the first part of the FRS. These fully identified fission residues impinged onto a 2.6 g/cm2 beryllium target located at the intermediate focal plane. The fragmentation products were also identified in the second section of the separator. In this contribution we present the measured production cross sections of this two-step reaction residues that are compared to direct production in 238U fission and 136Xe fragmentation, and with different model calculations.