Using relativistic mean field theory, the neutron and the proton density distribution of 56Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamics model, the 56Ni nuclei have been simulated in ground state and in the neutron or proton excited state. We then used the three different states of 56Ni to collide with the 56Ni in the ground state. To discuss the evolution of the nuclear stopping in different reactions, two kinds of different excited nuclear reactions were studied at different reaction energies and at different impact parameters. Studies have shown that the nuclear stopping of an excited nuclear reaction is sensitive to the isospin-dependent in-medium nucleon-nucleon cross section, compared with the response value of the ground state nuclear reaction. So, it is better for the excited nuclei to extract the isospin dependence of nucleon-nucleon cross section information.
This paper presents a new empirical formula to calculate the average nucleon-nucleon （N-N） collisi011 number for the total reaction cross sections （aR）. Based on the initial average N-N collision number calculated by quantum molecular dynamics （QMD）, quantum correction and Coulomb correction are taken into account within it. The average N-N collision number is calculated by this empirical formula. The total reaction cross sections are obtained within the framework of the Glauber theory, aR of 23A1＋1：C, anAl＋12C, 25A1＋12C, 26A1＋12C and 27A1＋12C are calculated in the range of low energy. We also calculate the an of 27A1＋12C with different incident e^ergies. The calculated aR are compared with the experimental data and the results of Glauber theory including the aa of both spherical nuclear and deformed nuclear. It is seen that the calculated aR are larger than GR of spherical nuclear and smaller than aa of deformed nuclear, whereas the results agree well with the experimental data in low-energy range.
In the framework of the isospin-dependent quantum molecular dynamics transport model （QMD）, the effects of symmetry potential on the collision number and the neutron-proton bremsstrahlung photon in the reactions of 40Ca＋40Ca, 124Sn＋124Sn, 40Ca＋64Zn, 40Ca＋124Sn at different incident beam energies are studied. It is found that the collision number shows moderate sensitivity to the stiffness of the symmetry potential and the number of hard photons calculated with stiff symmetry potential is obviously smaller than that with soft symmetry potential. Thus, the neutron-proton bremsstrahlung photons produced in heavy-ion collisions may be a useful probe for the high-density behavior of the nuclear symmetry potential.
Based on a modified quantum molecular the nuclear stopping of reaction systems with different dynamics model, we calculate the neutron-proton ratio and symmetry potentials and collision cross sections. We perform correlations of several probes using the covariance data processing method. It is shown that the correlation between the nuclear stopping and the isospin-dependent nucleon-nucleon cross sections is strong, but the nuclear stopping and symmetry potentials have a weak correlation. The correlation between neutron-proton ratio and symmetry potentials in the case of low energy is stronger. The correlation between neutron-proton ratio and isospin-dependent collision cross sections is enhanced with the increase of energy, but remains weak. In addition, the correlations of the emission numbers of the deuteron with the symmetry potentials and collision cross sections at different beam energies are not obvious compared to two prior physical quantities. In this paper, we define a parameter to quantitatively describe the sensitivity of isospin-dependent probes. By analyzing this parameter, one can extract more information about the isospin effects of the physical quantity.
基于同位旋相关的量子分子动力学模型,研究了对称势、束流能量、对称能强度系数对中能重离子碰撞反应系统的熵的影响。研究发现,对称势对熵有一定影响,且对熵的影响大小与反应系统中质比有关。另外发现在^(40)Ca+^(40)Ca和^(40)Si+^(40)Si反应系统中对称能强度系数对熵也有影响,当对称能强度系数c=32 Me V时,对这两个系统来说其对熵的影响最大。通过实验上对熵的测量可以得到对称势的形式和大小。
