Isospin effects and the density dependence of the nuclear symmetry energy

The density dependence of the nuclear symmetry energy is inspected using the statistical multifragmentation model with Skyrme effective interactions. The model consistently considers the expansion of the fragments’ volumes at finite temperature at the freeze-out stage. By selecting parametrizations of the Skyrme force that lead to very different equations of state for the symmetry energy, we investigate the sensitivity of the isoscaling parameter and the isotopic distributions to differences in the symmetry energy. Our results suggest that, in spite of being sensitive to the thermal dilation of the fragments’ volumes, it is difficult to distinguish among the Skyrme forces from the isoscaling analysis. On the other hand, the isotopic distribution of the emitted fragments turns out to be very sensitive to the force employed in the calculation.

Figure 1

Symmetry energy coefficient of cold nuclear matter for the SLy4 and Gs Skyrme forces as a function of the density $\rho$.

Figure 2

Isoscaling predicted by the SMM-TF using the SLy4 for $E^{*}/A=6.0$ MeV. In the upper panel, the yields of the hot primary fragments are used; the lower panel displays the results after the deexcitation of these fragments. The lines correspond to the best fit of the results using Eq. (1).

Figure 3

Isoscaling parameter $\alpha$ as a function of the excitation energy of the source, for different Skyrme forces and the ISMM, before and after the deexcitation of the primary fragments. The data are from Ref. [13].

Figure 4

Isotopic distribution of selected primary fragments for the Ar$\hspace{0.5em}+\hspace{0.5em}$Ni system at $E^{*}/A=8.5$ MeV.