NEUTRON ENRICHMENT OF THE NECK-ORIGINATED INTERMEDIATE MASS FRAGMENTS IN PREDICTIONS OF THE QMD MODEL

The effect of neutron enrichment of the neck formed during reseparation of two colliding nuclei was studied with the aim to infer an information on the density dependence of the asymmetry energy term in the equation of state. By using a version of the QMD model of Łukasik it is shown that the neutrons-to-protons ratio of the intermediate mass fragments (IMF) emitted from the neck, 〈N/Z〉, is not a sufficiently sensitive observable to discriminate between different assumptions regarding the symmetry term of the equation of state. As an alternative, isotopic ratios of selected pairs of isotopes turned out to be useful observables more sensitive to the assumed form of the symmetry term of the equation of state. A comparison with experimental data on isotopic ratios for beryllium and boron IMFs from the 124 Sn + 64 Ni reaction at 35 MeV/nucleon tentatively suggests that the ASY-SOFT option of the symmetry energy term in EOS is preferred.