中能重离子碰撞中前平衡核子发射的同位旋效应

Isospin Dependence of Preequilibrium Nucleon Emission in Intermediate Energy Heavy Ion Collision

利用同位旋相关的输运理论 ,研究了中能重离子碰撞中丰中子和缺中子碰撞系统在较宽能区范围内前平衡发射核子的同位旋效应 .结果表明除低能区外 ,在 10 0MeV/u以上核子 -核子碰撞动力学效应起主要作用的能区 ,前平衡发射的中子 -质子比仍然对介质中核子 -核子碰撞截面的同位旋效应不灵敏 ,然而对于对称势的改变非常灵敏 .故从低能量到较高能量的较大能区内 ,前平衡发射的中子

The isospin dependence of preequilibrium nucleon emission for the neutron deficient colliding system and neutron rich system has been studied in the wide beam energy region. The calculation results show that the ratio of preequilibrium emission neutrons to protons is sensitive to the symmetrical potential and insensitive to the isospin dependence of in medium nucleonnucleon collision cross section from low beam energy region to high energy region, in which nucleonnucleon collision dynamics is dominant, namely the isospin dependence of in medium nucleonnucleon cross section excites neutron and proton to be emitted with about the same probability in wide beam energy region. At the same time, the neutrons and protons are excited to be emitted with the same probability for Pauli potential, momentum dependence interaction and impact parameter, even though their effects on preequilibrium neutron number and proton number are obvious. The ratio of preequilibrium neutrons to protons for neutron rich colliding system is larger than the initial value of neutron proton ratio of colliding system, but that for neutron deficient system is less than the initial value. In this case, one can compare the theoretical results with the experimental data systematically to extract information on the symmetrical potential.