Effect of coulomb interaction on isospin fractionation process

The authors studied the effect of Coulomb interaction on the isospin fractionation in intermediate energy heavy ion collisions by using isospin dependence quantum molecular dynamics model (IQMD). The results show that Coulomb interaction reduces the isospin fractionation process whatever the system mass, beam energy and system neutron-proton ratio are, because Coulomb interaction is repulsive for proton. The more bound protons became free under Coulomb interaction, which produces neutron-poor gas phase and neutron-rich liquid phase, thus isospin fractionation degree is weaken. On the contrary, the symmetry potential is repulsive for neutrons and attractive for protons in neutron-rich systems. The bound neutrons more than protons became free, which produces neutron-rich gas phase and neutron-poor liquid phase, so the isospin fractionation degree increases. Total effects of the Coulomb interaction and symmetry potential make the isospin fractionation degree to be in between those induced by themselves individually