Fragment Distribution In Heavy-ion Collisions At Low And Intermediate Energies

In this thesis, we studied the distributions of kinetic energy of the fragments, charges and isotopes which generated from the heavy-ion collisions at low and interme-diate energies, based on the improved quantum molecular dynamics model (ImQMD-v2.2) together with the statistical decay model (GEMINI). The simulation results is consistent with the experimental data, which helps us to understand the mechanis-m of deep inelastic scattering and the dynamic processes of nuclear collision. Before the simulation of ions collision, the reliability and stability of the ImQMD-v2.2 model had been checked by testing the ground properties of nucleons.such as binding energy, root mean square radius etc. From the distribution of the total kinetic energy (TKE ) of reaction system of near-barrier 16O+40Ca and 154Sm+162Gd, the phenomenon of multi-nucleon transfer can be observed an central and semi-central collisions.The hybrid model (ImQMD-v2.2+GEMINI) is used to simulate the reaction of 197Au+197Au at E= 35 MeV/u, and the calculated results are in good agreement with the experimental data at central collisions, even without using the statistical de-cay model. However, at the peripheral collisions, the yields of heavy-mass fragments are over-predicted and the yields of median-mass fragments are under-predicted if ne-glecting the secondary decay of primary fragments. By using the code of GEMINI for describing the secondary decay of primary fragments, the charges distribution of 197Au+197Au at E = 35 MeV/u can be reproduced reasonably well.We also studied the isotopic distribution of 154Sm+162Gd at the centre-mass energy Ec.m.=440MeV. The experimental results show that the yields of neutron-rich isotopes are much larger than the proton-rich ones, and some new neutron-rich isotopes can be produced. We also calculated the isotopic distribution of 154Sm+154Sm and 238U+238U at the incident energy of E= 35 MeV/u. We found that in the influence of statistical decay is very obvious. The yields of neutron-rich nuclei are reduced by symmetric or asymmetric fission、 particle evaporation and so on. In the heavy ion collisions at intermediate-energies regions, we did not observe obvious new neutron-rich isotopes. Multi-nucleon transfer reactions at energies near the coulomb barrier could be a new way to produce new neutron-rich isotopes.