ISOSPIN EQUILIBRIUM AND NONEQUILIBRIUM IN INTERMEDIATE ENERGY HIC

采用同位旋相关的ＱＭＤ模型探讨了同位旋的平衡与非平衡．此ＱＭＤ模型包含了同位旋相关的对称能、库仑能、Ｎ－Ｎ截面和Ｐａｕｌｉ阻塞．观察到随着入射能量超过某一阀能存在着同位旋由平衡到非平衡的跃迁，发现这种现象是由不同反应机制的共存与竞争所导致的，即当ＩＣＦ（非完全熔合）分量占主导时同位旋平衡能够达到，而当碎裂分量占主导时同位旋平衡受到破坏．

ISOSPIN EQUILIBRIUM AND NONEQUILIBRIUM IN INTERMEDIATE ENERGY HIC

The isospin equilibrium and nonequilibrium are studied in terms of an isospin dependent QMD model, which includes isopin dependent symmetry energy, Coulomb energy, N N cross sections and Pauli blocking. It is shown that there exists a transition from the isospin equilibrium to nonequilibrium as the incident energy from below to above a threshold energy in central, asymmetric heavy ion collisions. Meanwhile, it is found that the phenomenon results from the coexistence and competition of different reaction mechanisms, namely, the isospin reaches an equilibrium if the incomplete fusion (ICF) component is dominant and does not reach equilibrium if the fragmentation component is dominant.