摘要
Effect of isospin dependence of nucleon-nucleon (N-N) cross sectionσNNiso on the isospin fractionation ratio (n/p)free/(n/p)liq as the increase of neutron-proton ratio of collision system (n/p)sys is investigated in heavy ion collisions. Where the isospin independent N-N cross sectionsσ1noiso andσ2noiso are defined asσnn=σpp =σnp(σ1noiso) andσnn=σpp=(1/2) (σnp+σnn)(σ2noiso) respectively. An empirical density dependent expression of the in-medium N-N cross section
Effect of isospin dependence of nucleon-nucleon （N-N） cross sectionσNNiso on the isospin fractionation ratio （n/p）free/（n/p）liq as the increase of neutron-proton ratio of collision system （n/p）sys is investigated in heavy ion collisions. Where the isospin independent N-N cross sectionsσ1noiso andσ2noiso are defined asσnn=σpp =σnp（σ1noiso） andσnn=σpp=（1/2） （σnp＋σnn）（σ2noiso） respectively.
