Quasiprojectile and intermediate velocity isotopic ratios for light fragments emitted in the Ar 36 +Ni 58 and Ni 58 +Ni 58 reactions between 32A and 84A MeV

Expérience GANILIsotopic ratios for light fragments (Z≤4 ) emitted by the quasiprojectile (QP) and the mid-rapidity (MR) sources are investigated by the use of a slightly asymmetric system (Ar 36 +Ni 58 ) and a symmetric one (Ni 58 +Ni 58 ) for six energies between 32A and 84A MeV and three semiperipheral centrality range selections. Experimental data come from the INDRA 4π multidetector. The results show a clear neutron-rich isotope production from the MR region as compared to the QP source. The beam energy and the centrality also show interesting different trends depending on the charge of the fragments and the emission source. Experimental results are compared to antisymmetrized molecular dynamics simulations

New isospin effects in central heavy-ion collisions at Fermi energies

10 pages. 6 figures. Submitted to Physical Review C.Isospin e ffects on multifragmentation properties were studied thanks to nuclear collisions between di fferent isotopes of xenon beams and tin targets. It is shown that, in central collisions leading to multifragmentation, the mean number of fragments and their mean kinetic energy increase with the neutron-richness of the total system. Comparisons with a stochastic transport model allow to attribute the multiplicity increase to the multifragmentation stage, before secondary decay. The total charge bound in fragments is proposed as an alternate variable to quantify preequilibrium emission and to investigate symmetry energy e ffects