Isoscaling Behaviour in the Isospin-Dependent Quantum Molecular Dynamics Model

The isoscaling behaviour is investigated in a frame of isospin-dependent quantum molecular dynamics models. The isotopic yields ratio Y2/Y1 for reactions ^48Ca ^48Ca and ^40 Ca ^4oCa at different entrance channels are simulated and presented, the relationship between the isoscaling parameter and the entrance channel is analysed, the results show that a and β reduce with the rise of incident energies and increase with the impact parameter b, which can be attributed to the temperature varying of the pre-fragments in different entrance channels. The relation of a and symmetry-term coefficient Csym reveals that the chemical potential difference △μ is sensitive to thesymmetry-term coefficient Csym, and raises with the increasing Csym.     

Isoscaling in Statistical Sequential Decay Model

A sequential decay model is used to study isoscaling, i.e. the factorization of the isotope ratios from sources of different isospins and sizes over a broad range of excitation energies, into fugacity terms of proton and neutron number, R21（N, Z） = Y2（ N, Z）/Y1（ N, Z） = Cexp（αN -βZ）. It is found that the isoscaling parameters α and β have a strong dependence on the isospin difference of equilibrated source and excitation energy, no significant influence of the source size on α andβ has been observed. It is found that α and β decrease with the excitation energy and are linear functions of 1/T and △（Z/A）2 or△（N/A）2 of the sources. Symmetry energy coefticient Gsym is constrained from the relationship of a and source △（Z/A）2, /3 and source △（N/A）2.     

Transverse radius dependence for transverse velocity and elliptic flow in intermediate energy HIC

The mean transverse velocity and elliptic flow of light fragments (A ≤ 2) as a function of transverse radius are studied for 25 MeV/nucleon ⁶⁴Cu+⁶⁴Cu collisions with impact parameters 3--5 fm by the isospin-dependent quantum molecular dynamics model. By comparison between the in-plane and the out-of-plane transverse velocities, the elliptic flow dependence on the transverse radius can be understood qualitatively, and variation of the direction of the resultant force on the fragments can be investigated qualitatively.     

Energy dependence for directed and elliptic flow in in termediate-energy heavy ion collisions

Differential and integrated directed flow and elliptic flow of light charged particles （z≤2） are studied systematically for semi-central （b=5 fm）¹⁹⁷ Au+197 Au collisions at incident energies from 25 to 250 MeV/nucleon by the isospin-dependent quantum molecular dynamics model. The changes of directed and elliptic flow with incident energy reflect the dynamic competition between the mean field and nucleon-nucleon collisions and also between collective rotation and expansion.     

23Al及其邻近丰质子核的奇异结构研究

在RIKEN-RIPS上测量了²³Al等丰质子核素的核反应总截面(σ_R)和平行动量分布(P^//). 观察到了²³Al核反应总截面的增强, 与以前的实验结果相符. 同时得到了²³Al等丰质子核素擦掉一个质子后的P_//. 在Few-body Glauber模型下对实验结果进行了讨论. P_//的宽度显示²³Al基态的外层质子处于d态, 这与g因子测量实验结果一致. 为了同时解释P_//和σ_R的实验测量结果, 我们认为²³Al可能有核芯增大的现象.     

弹核碎裂反应的同位旋标度率及核的对称能系数研究

用统计擦碎模型对中能区弹核碎裂反应中的同位旋标度率现象进行了系统研究. 发现在弹核碎裂反应中存在同位旋标度率现象, 但同位旋标度率参数随每核子的激发能的增加迅速下降. 而影响同位旋标度率参数变化的最主要的因素是由于激发能不同及蒸发效应. 采用费米气体模型的激发能与核温度的关系, 从同位旋标度率参数提取出核的对称能系数, 值的大小及其与激发能的变化趋势跟实验数据基本一致.     

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field （RMF） model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that ^19,29,32Ne and ^20,31Mg maybe have a triaxial deformation and ^25-28Ne and ^27-30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for ^20Mg is predicted to be very weak.     

Cross Sections of Elastic Electron and Positron Scattering from Proton-Rich Nuclei

We investigate the cross sections of the elastic electron or positron scat tering from 208 Pb, ^12C ^12,16O and ^28,32S by the relativistic partial-wave expansion method using the static charge density distribution from the self-consistent relativistic mean fiel model and also calculate the charge form factor for ^12＇16O and ^28,32S. The numerical results are compared with the available data. Calculations indicate that the extended charge density distributions of ^12O and ^28S have observable effects on the cross sections of the electron or positron scattering as well as the charge form factors.     

中能重离子碰撞中集体流标度性质研究

利用同位旋相关的量子分子动力学模型模拟了40Ca+40Ca,50Ca+40Ca,64Cu+64Cu和197Au+197Au等多个碰撞系统中快度轻碎片集体流标度的性质。发现,中能区不同碰撞系统横向动量相关的椭圆流存在对碎片核子数的标度,且存在v4/v22标度,对不同碎片该比值都近似为常数0.5。同时探讨了碰撞能量、碰撞参数、核状态方程对标度律的影响,发现这些标度行为不敏感于以上物理量,可能是核碎片形成机制(组合机制)的必然结果。     

Studies on the exotic structure of 23Al

The longitudinal momentum distribution (P_//) of fragments after one-proton removal from ²³Al and reaction cross sections (σ_R) for ^23,24Al on carbon target at 74A MeV have been measured simultaneously. An enhancement in σ_R is observed for ²³Al compared with ²⁴Al. The full width at half maximum of the P_// distribution for ²²Mg fragments has been determined to be 232±28 MeV/c. Analysis of P_// using the Few-Body Glauber Model indicates a dominant d-wave configuration for the valence proton in the ground state of ²³Al. The exotic structure in ²³Al is discussed.