摘要
Effect of isospin dependence of nucleon-nucieon cross sectionσNNiso on the neutron-proton ratio of nucleon emissions (n/p)free 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 sectionσ1noiso andσ2noiso are defined asσnn=σpp =σnp(σ1noiso) andσnn=σpp= (1/2)(σnp+σnn) (σ2noiso) respectively. Because the isospin dependent in-medium N-N cross sectionσNNiso,especially the neutron-proton to proton-proton (neutron-neutron) cross section
Effect of isospin dependence of nucleon-nucieon cross sectionσNNiso on the neutron-proton ratio of nucleon emissions （n/p）free 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 sectionσ1noiso andσ2noiso are defined asσnn=σpp =σnp（σ1noiso） andσnn=σpp= （1/2）（σnp＋σnn） （σ2noiso） respectively. Because the isospin dependent in-medium N-N cross sectionσNNiso,
