利用同质异位素产额比提取对称能的近似方法

在修改的Fisher模型框架下, 利用同质异位素产额比和结合能方程中对称能系数与温度比率的关联, 可以提取对称能系数与温度的比值。 利用3种不同的近似方法得到了重离子核反应产生丰中子余核的对称能系数与温度比（a_sym/T）,并研究了相关物理量对a_sym/T的影响。结果表明, 库仑能对提取丰中子余核的a_sym/T影响较小,且参考核的选取对a_sym/T的提取也有一定的影响。 In the framework of the modified Fisher model, correlations between the symmetry energy coefficient in semi classical mass formula to temperature (a_sym/T) and the isobaric yield ratio in Heavy ion collisions are established. a_sym/Tof neutron rich fragments are extracted using these correlations. It is found that the Coulomb energy term has little effect on a_sym/T of fragments, while the reference isobars adopted have great influence on the extracted a sym/T of fragments.     

利用同质异位素产额比提取对称能的近似方法

在修改的Fisher模型框架下,利用同质异位素产额比和结合能方程中对称能系数与温度比率的关联,可以提取对称能系数与温度的比值。利用3种不同的近似方法得到了重离子核反应产生丰中子余核的对称能系数与温度比（asym/T）,并研究了相关物理量对asym/T的影响。结果表明,库仑能对提取丰中子余核的asym/T影响较小,且参考核的选取对asym/T的提取也有一定的影响。     

Symmetry energy from neutron-rich fragments in heavy-ion collisions, and its dependence on incident energy, and impact parameters

The yields of fragments produced in the 60Ni+ 12C reactions at 80 A and 140 A MeV, and with maximum impact parameters of 1.5, 2 and 7.3 fm at 80 A MeV are calculated by the statistical abrasion-ablation model. The yields of fragments are analyzed by the isobaric yield ratio (IYR) method to extract the coefficient of symmetry energy to temperature (asym/T ). The incident energy is found to influence asym/T very little. It’s found that asym/T of fragments with the same neutron-excess I = N-Z increases when A increases, while asym/T of isobars decreases when A increases. The asym/T of prefragments is rather smaller than that of the final fragments, and the asym/T of fragments in small impact parameters is smaller than that of the larger impact parameters, which both indicate that asym/T decreases when the temperature increases. The choice of the reference IYRs is found to have influence on the extracted a sym /T of fragments, especially on the results of the more neutron-rich fragments. The surface-symmetry energy coefficient (bs/T ) and the volume-symmetry energy coefficient (bv/T) are also extracted, and the bs/bv is found to coincide with the theoretical results.     

Temperature of Heavy Fragments in Heavy-Ion Collisions

The heavy fragments in heavy-ion collisions are finally formed after the hot prefragments undergo sequential decay,of whom the temperature should be much lower than that of prefragments.Using the double ratio(DR) method,the isotopic thermometer(Tiso) for heavy fragment is constructed using the yield of heavy isotopes.T iso of heavy fragment is obtained by analyzing the measured data in the 1A GeV124,136Xe and 140A MeV 48Ca/64Ni reactions.Result shows that T iso varies from 0.5 MeV to 10 MeV.But most T iso is around 1±0.5 MeV,which is much lower than temperature of light particles.Result also indicates that the difference between T iso of heavy fragments in different reactions is very small,and T iso is independent on the size of the reaction system,the incident energy and the neutron-richness of the projectile.