Isospin effect of Coulomb interaction on the dissipation and fragmentation in intermediate energy heavy ion collisions

We investigate separately the isospin effects of Coulomb interaction and symmetry potential on the dissipation and fragmentation in the intermediate energy heavy ion collisions by using isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces the reductions of both isospin fractionation ratio and nuclear stopping (momentum dissipation). However, the Coulomb interaction not only does not change obviously the strong isospin effect of the symmetry potential on the isospin fractionation ratio but also does not change obviously that of in-medium two-body collision on the nuclear stopping. On the contrary, the symmetry potential induces the enhancement of the isospin fractionation ratio but it is insensitive to the nuclear stopping. Finally, the competition between the Coulomb interaction and symmetry potential induces the reductions of both isospin fractionation ratio and nuclear stopping for two forms of symmetry potentials in this paper.

Figure 1

The ${(N∕Z)}_{\text{gas}}∕{(N∕Z)}_{\mathrm{liq}}$ as a function of neutron-proton ratio of system at the beam energy of $50\mathrm{MeV}∕\text{nucleon}$ and impact parameter $b=2.0\mathrm{fm}$ with and without Coulomb terms.

Figure 2

The ${(N∕Z)}_{\text{gas}}∕{(N∕Z)}_{\mathrm{liq}}$ as a function of system mass with and without Coulomb interactions at a beam energy of $50\mathrm{MeV}∕\text{nucleon}$ and an impact parameter of $2.0\mathrm{fm}$.

Figure 3

The time evolution of ${(N∕Z)}_{\text{gas}}$ (left window) and ${(N∕Z)}_{\mathrm{liq}}$ (right window) for three cases for the reaction ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at a beam energy of $50\mathrm{MeV}∕\text{nucleon}$ and impact parameter of $2.0\mathrm{fm}$.

Figure 4

The time evolution of ${(N∕Z)}_{\text{gas}}$ (left window) and ${(N∕Z)}_{\mathrm{liq}}$ (right window) for three systems at $E=50\mathrm{MeV}∕\text{nucleon}$ and $b=2.0\mathrm{fm}$.

Figure 5

The $R$ as a function of beam energy with and without Coulomb interactions as well as for the reaction ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at impact parameter $b=2.0\mathrm{fm}$.

Figure 6

The $R$ as a function of system mass with and without Coulomb interactions at beam energy $E=100\mathrm{MeV}∕\text{nucleon}$ and impact parameter $b=2.0\mathrm{fm}$.

Figure 7

The time evolution of $R$ for the reaction ${}^{89}\mathrm{Kr}+{}^{89}\mathrm{Kr}$ at a beam energy of $50\mathrm{MeV}∕\text{nucleon}$ and impact parameter of $2.0\mathrm{fm}$.

Figure 8

The time evolution for rms error of $R$ (left window) and that of ${(N∕Z)}_{\text{gas}}∕{(N∕Z)}_{\mathrm{liq}}$ (right window) for 100 events and for the reaction ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at an impact parameter $b$ of $2.0\mathrm{fm}$ and beam energy of $50\mathrm{MeV}∕\text{nucleon}$.