Probing equilibration with respect to isospin degree of freedom in intermediate energy heavy ion collisions

Abstract

We have studied equilibration with respect to isospin degree of freedom in four 96 mass systems $^{96}Ru+^{96}Ru$, $^{96}Ru+^{96}Zr$, $^{96}Zr+^{96}Ru$, $^{96}Zr+^{96}Zr$ at 100 AMeV and 400 AMeV with isospin dependent QMD. We propose that the neutron-proton differential rapidity distribution is a sensitive probe to the degree of equilibration with respect to the isospin degree of freedom. By analyzing the average $N/Z$ ratio of emitted nucleons, light charged particles (LCP) and intermediate mass fragments (IMF), it is found that there exist memory effect in multifragmentation process. The average $N/Z$ ratio of IMF reduces largely as beam energy increases from 100 AMeV to 400 AMeV which may result from the change of the behavior of the isotope distribution of IMF charges. The isotope distribution of IMF charges does also show certain memory effect at 100 AMeV case but not at 400 AMeV case.

12 papers, 5 figures, accepted by PRC