Influence of neutron enrichment on compound system formation and decay in 78Kr+40Ca and 86Kr+48Ca reactions at 10 AMeV

The de-excitation of medium mass nuclei 118,134Ba produced in fusion process of 78,86Kr on 40,48Ca targets at 10 AMeV is studied, in order to investigate the isospin dependence of the decay modes; the neutron enrichment of the compound nuclei is in fact expected to play an important role on the emission mechanisms, providing crucial information on fundamental nuclear quantities such as level density, fission barrier, viscosity and symmetry energy. The experiment was performed at INFN-LNS with the 4π multidetector for charged particles CHIMERA, used for the first time in this low energy regime, thanks to a suitable Pulse Shape Discrimination method for charge identification applied to the silicon detectors. Preliminary results show a different isotopic composition and relative enrichment for the same Z in the two systems. The yields of the Intermediate Mass Fragments (IMF, 3<Z<12) exhibits a strong even-odd staggering, more pronounced for the n-poor system. The IMF energy spectra show some differences according to the entrance channel and to the charge and mass of the fragment.