Dynamical and many-body correlation effects in the kinetic energy spectra of isotopes produced in nuclear multifragmentation

The properties of the kinetic energy spectra of light isotopes produced in the breakup of a nuclear source and during the de-excitation of its products are examined. The initial stage, at which the hot fragments are created, is modeled by the statistical multifragmentation model, whereas the Weisskopf-Ewing evaporation treatment is adopted to describe the subsequent fragment de-excitation, as they follow their classical trajectories dictated by the Coulomb repulsion among them. The energy spectra obtained are compared to available experimental data. The influence of the fusion cross section entering into the evaporation treatment is investigated and its influence on the qualitative aspects of the energy spectra turns out to be small. Although these aspects can be fairly well described by the model, the underlying physics associated with the quantitative discrepancies remains to be understood.

Figure 1

Experimental kinetic energy of selected isotopes produced in the collision of ${}^{112}\mathrm{Sn}$ + ${}^{112}\mathrm{Sn}$ nuclei [25].

Figure 2

Fusion cross section for the collision between ${}^3\mathrm{He}$ + ${}^9\mathrm{Be}$ nuclei as a function of the relative energy. The curves correspond to parametrizations used in different models. For details, see the text.

Figure 3

Energy spectra of selected fragments produced in the breakup of the $A_0=168$ and $Z_0=75$ nucleus (a) at $T=5.0$ MeV and $E_{\mathrm{flow}}/A=1.5$ MeV, (b) at $T=4.8$ MeV and $E_{\mathrm{flow}}/A=0.5$ MeV, (c) at $T=5.2$ MeV and $E_{\mathrm{flow}}/A=0.5$ MeV, and (d) at $T=5.0$ MeV, $E_{\mathrm{flow}}/A=0.5$ MeV, for the source $A_0=112$ and $Z_0=50$. For details see the text.

Figure 4

Energy spectra of selected fragments produced in the breakup of the $A_0=168$ and $Z_0=75$ nucleus, at $T=5$ MeV and $E_{\mathrm{flow}}/A=0.5$ MeV. The spectra associated with the primary fragments are displayed in (a) whereas those obtained with final yields are exhibited in (b), (c), and (d). The final fragment distributions are obtained considering the evaporation of nuclei with mass number up to 4 (b), 6 (c), and 10 (d). For details see the text.

Figure 5

Energy spectra of selected fragments produced in the breakup of the $A_0=168$ and $Z_0=75$ nucleus, at $T=5$ MeV and $E_{\mathrm{flow}}/A=0.5$ MeV. The partial decay widths are calculated using the fusion cross sections employed (a) in the EES model [15] and (b) in the standard SMM [39]. Only fragments with $A\le 4$ are allowed to be emitted in the de-excitation process. For details see the text.