Isospin fractionation in the nucleon emissions and fragment emissions in the intermediate energy heavy ion collisions
Abstract The degree of isospin fractionation is measured by ( N / Z ) n /( N / Z ) N imf , where ( N / Z ) n and ( N / Z ) N imf are the saturated neutron–proton ratio of nucleon emissions (gas phase) and that of fragment emissions (liquid phase) in heavy ion collision at intermediate energy. The calculated results by using the isospin-dependent quantum molecular dynamics model show that the degree of isospin fractionation is sensitive to the neutron–proton ratio of colliding system but insensitive to the difference between the neutron–proton ratio of target and that of projectile. In particular, the degree of isospin fractionation sensitively depends on the symmetry potential. However, its dependences on the isospin dependent in-medium nucleon–nucleon cross section and momentum dependent interaction are rather weak. The nucleon emission (gas phase) mainly determines the dynamical behavior of the degree of isospin fractionation in the isospin fractionation process, compared to the effect of fragment emission. In this case, we propose that ( N / Z ) n /( N / Z ) N imf or ( N / Z ) n can be directly compared with the experimental data so that the information about symmetry potential can be obtained.
Probing the nuclear symmetry energy with heavy-ion reactions induced by neutron-rich nuclei
Heavy-ion reactions induced by neutron-rich nuclei provide a unique means to investigate the equation of state of isospin-asymmetric nuclear matter, especially the density dependence of the nuclear symmetry energy. In particular, recent analyses of the isospin diffusion data in heavy-ion reactions have already put a stringent constraint on the nuclear symmetry energy around the nuclear matter saturation density. We review this exciting result and discuss its implications on nuclear effective interactions and the neutron skin thickness of heavy nuclei. In addition, we also review the theoretical progress on probing the high density behaviors of the nuclear symmetry energy in heavy-ion reactions induced by high energy radioactive beams.
The single particle potential in nuclear matter
Abstract The energy dependent real part of the optical potential for particles and holes in nuclear matter is calculated from a realistic nuclear hamiltonian that explains the nucleon-nucleon scattering data and equilibrium properties of nuclear matter. The variational method is used with Fermi-hypernetted and single-operator-chain summation techniques. The results are comparable with empirical Woods-Saxon well depths at energies ≲ 150 MeV. At higher energies the potential has a density dependence suggesting a “wine-bottle” shaped nucleon-nucleus potential.