Isospin Fractionation Process in Intermediate Energy Heavy Ion Collisions

GUO Wen-Jun; LIU Jian-Ye; XING Yong-Zhong; ZUO Wei; LI Xi-Guo

Chinese Physics C> 2003, Vol. 27> Issue(10) : 897-900

Isospin Fractionation Process in Intermediate Energy Heavy Ion Collisions

Center of Theoretical Nuclear Physics,National Laboratory of Heavy Ion Accelerator,Lanzhou 730000,China2 Institute of Modern Physics,CAS,Lanzhou 730000,China3 Institute for the Theory of Modem Physics,Tianshui Normal College,Tianshui 741000,China

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Abstract：
The isospin fractionation in intermediate energy heavy ion collisions is studied by using isospin dependence quantum molecular dynamics model. At first, the reaction productions in isospin fractionation process is separated into a gas phase and a liquid phase. The gas phase includes free neutrons and protons. But there are many choices for the liquid phase, we select the fragments from the region of 1P+Z_T)/2 as the liquid phase, here Z, Z_P and Z_T are charge of the fragment, projectile and target, respectively. For considering the influence of projectile-like and target-like , we choose the upper limit of charges to (Z_P+Z_T)/2. We define the degree of isospin fractionation as a ratio of gas phase neutron-proton ratio (N/Z)_gas to liquid phase neutron-proton ratio (N/Z)_liq. The calculated results show that the degree of isospin fractionation is sensitive to the symmetry potential and insensitive to isospin dependent neucleon-neucle-on cross section. This sensitivity mainly comes from the gas part of the isospin fractionation. The liquid part is insensitive to the symmetry potential. So we may compare the theory calculation results with the experimental data directly to get the knowledge of symmetry potential. The calculated results also show that the ( N/Z)_gas is larger than the (N/Z)_sys of the colliding system but the (N/Z)_liq is less than the (N/Z)_sys for the neutron-rich system. Finally, the isospin fractionation process is not sensitive to the choices for the fragments of liquid phase.

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GUO Wen-Jun, LIU Jian-Ye, XING Yong-Zhong, ZUO Wei and LI Xi-Guo. Isospin Fractionation Process in Intermediate Energy Heavy Ion Collisions[J]. Chinese Physics C, 2003, 27(10): 897-900.

GUO Wen-Jun, LIU Jian-Ye, XING Yong-Zhong, ZUO Wei and LI Xi-Guo. Isospin Fractionation Process in Intermediate Energy Heavy Ion Collisions[J]. Chinese Physics C, 2003, 27(10): 897-900. shu

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Received: 2002-11-18
Revised: 1900-01-01

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通讯作者: 陈斌, bchen63@163.com

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沈阳化工大学材料科学与工程学院沈阳 110142

Isospin Fractionation Process in Intermediate Energy Heavy Ion Collisions

Corresponding author: GUO Wen-Jun,

Center of Theoretical Nuclear Physics,National Laboratory of Heavy Ion Accelerator,Lanzhou 730000,China2 Institute of Modern Physics,CAS,Lanzhou 730000,China3 Institute for the Theory of Modem Physics,Tianshui Normal College,Tianshui 741000,China

Received Date: 2002-11-18

Accepted Date: 1900-01-01

Available Online: 2003-10-05

Abstract: The isospin fractionation in intermediate energy heavy ion collisions is studied by using isospin dependence quantum molecular dynamics model. At first, the reaction productions in isospin fractionation process is separated into a gas phase and a liquid phase. The gas phase includes free neutrons and protons. But there are many choices for the liquid phase, we select the fragments from the region of 1P+Z_T)/2 as the liquid phase, here Z, Z_P and Z_T are charge of the fragment, projectile and target, respectively. For considering the influence of projectile-like and target-like , we choose the upper limit of charges to (Z_P+Z_T)/2. We define the degree of isospin fractionation as a ratio of gas phase neutron-proton ratio (N/Z)_gas to liquid phase neutron-proton ratio (N/Z)_liq. The calculated results show that the degree of isospin fractionation is sensitive to the symmetry potential and insensitive to isospin dependent neucleon-neucle-on cross section. This sensitivity mainly comes from the gas part of the isospin fractionation. The liquid part is insensitive to the symmetry potential. So we may compare the theory calculation results with the experimental data directly to get the knowledge of symmetry potential. The calculated results also show that the ( N/Z)_gas is larger than the (N/Z)_sys of the colliding system but the (N/Z)_liq is less than the (N/Z)_sys for the neutron-rich system. Finally, the isospin fractionation process is not sensitive to the choices for the fragments of liquid phase.

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