| Up to now, great progress on the study of the equation of status (EoS) of symmetric nuclear matter has been acheived, but the knowledge of isospin asymmetric nuclear equation of state is still less known. The key point to constrain the isospin asymmetric nuclear equation of state is to extract the information of symmetry energy term since the isospin asymmetric nuclear equation of state are composed by the symmetric and asymmetric part. A consensus on the constraints of symmetry energy at subsaturation density has been obtained in last ten years, but differences of these constraints are still exist among different models or approaches. Understanding these differences becomes a challenge in current studies, and hence stimulates nuclear physicist to propose new probes that are sensitive enough on the further discrimination of the stiffness of symmetry energy and then to perform new experiments for a comprehensive understanding of the mechanism of neutron-rich heavy ion collisionsThe purpose of this thesis is to understand the mechanism of the neutron-rich Heavy ion Collisions at low-intermediate energy and do further exploration about density dependence symmetry energy by using the ImQMD model. The collision systems are 40Ar+112Sn,124Sn,197Au,238U, the reduced impact parameter is -0.6 and the incident energy varies from 35 to 100MeV/u.Firstly, we focus our attention on the source of the anisotropy of the dynamic emission of Light Particles (LPs). It was found that the LPs of dynamic emission are mainly come from the overlapped region of projectile and target. And, the time evolution of density, isospin asymmetry, symmetrical potential and single particle potential are investigated. The simulation results show that the competition between coulomb potential and symmetry potential play vital roles on the understanding of the yields and its isospin contents of dynamics emission of LPs.Then, we propose the Coalescence Invariant Angular Distribution to analysis the density dependence of symmetry energy by using low-intermediate energy heavy ion collisions. The result shows that the CI-n/p values at forward region increased with the increasing of θcm. for γi= 0.5, and the opposite behaviors appears for γi=2.0, i.e. the CI-n/p values decrease with θc.m..To quantitatively describe the anisotropy of CI-n/p, Riso1=Rn/p(20°)/Rn/p(90°) was constructed, and our results show that Risol is strong correlation with the slope of symmetry energy. When we cut off the part that their energy are less than 10MeV/u, the sensitive of Risol to L become more stronger.Furthermore, we analyze some others reaction systems to understand its’ dependence on system size, asymmetry of reaction system and isospin asymmetry of reaction system. By comparing the results obtained with 40Ar+112Sn and 40Ar+124Sn, we found that neutron rich target in the reaction system weak the angular anisotropy of the dynamic emission of LPs. By comparing the results from 40Ar+112Sn, 40Ar+197Au we found the larger the target is, the more obvious the anisotropy the dynamic emission of the LPs. However, this conclusion also depends on the state of initial nucleus that have not been extensively studied in this thesis. |
