Evaporation and fission of the primary fragments produced by multinucleon transfer reactions

The multinucleon transfer (MNT) reaction has aroused wide interest in recent years largely due to its ability to produce neutron-rich heavy nuclei. The semiclassical model GRAZING can describe well the experimental MNT data for many medium-heavy systems, but only simply considers neutron evaporation in the deexcitation of primary fragments. In order to describe the final MNT products for heavy and even superheavy systems, we try to consider both the transfer and subsequent deexcitation processes by combining, for the first time, the GRAZING model and the statistical-decay model GEMINI as well as the improved version GEMINI++. Considering fission in the deexcitation of primary fragments by GEMINI++ model, the isotope distributions of final fragments are much wider than those only by GRAZING model, indicating an important role of fission in the deexcitation process for heavy and superheavy fragments. However, our results have large deviations from the GRAZING-F results, which may result from the different technique adopted in the deexcitation process. Moreover, it is shown that the GEMINI++ model is more reasonable than the GEMINI model, because the latter overpredicts the fission probability and the width of fission isotope distributions to a large extent. With GEMINI++ model, the predictions of cross sections for final isotopes can be improved by taking into account charged-particle evaporations, especially the $\alpha$ evaporation.

Figure 1

Projectilelike isotopic production cross sections for ${}^{64}\mathrm{Ni}+{}^{238}\mathrm{U}$ at $E_{\mathrm{c}.\mathrm{m}.}=307.5$ MeV. The experimental data from Ref. [68] are shown as solid circles. The dashed (Gra-Pri) and dash-dotted lines (Gra-Fin) represent the primary fragments and final fragments generated by the original GRAZING model. Final fragments produced by GRAZING complemented with GEMINI and GEMINI++ are represented by solid (Gm) and the dotted lines (Gm++), respectively.

Figure 2

Same as Fig. 1 but for the distribution with neutron number.

Figure 3

Same as Fig. 1 but for the distribution with proton number. The dash-dotted and the solid lines almost overlap for $Z=22–30$.

Figure 4

Targetlike isotopic production cross sections for ${}^{238}\mathrm{U}+{}^{238}\mathrm{U}$ at $E_{\mathrm{lab}}=1628$, 1785, 2059 MeV. The experimental data from Ref. [13] are shown as solid circles. The dashed (Gra-Pri) lines represent the primary fragments predicted by the original GRAZING. The predictions shown as the dash-dotted lines are calculated by GRAZING-F [49]. Final fragments predicted by GRAZING plus GEMINI and GEMINI++ are represented by solid (Gm) and the dotted lines (Gm++), respectively.

Figure 5

Same as Fig. 4 but for ${}^{136}\mathrm{Xe}+{}^{248}\mathrm{Cm}$ at $E_{\mathrm{lab}}=769$ MeV. The experimental data are obtained from Ref. [69].

Figure 6

Primary projectilelike and targetlike isotopic production cross sections of the MNT reaction ${}^{136}\mathrm{Xe}+{}^{248}\mathrm{Cm}$ at $E_{\mathrm{lab}}=769$ MeV, which are calculated with GRAZING model. The black lines represent the assumed positions of corresponding neutron and proton shells. The enlarged targetlike fragment distribution is plotted as the insert located at the bottom right position, which shares the same coordinate systems.

Figure 7

Same as Fig. 6 but for final targetlike isotopic production cross sections, which are calculated with GRAZING plus GEMINI++ model. The cross symbols denote the locations of the projectile and target.

Figure 8

Same as Fig. 6 but for final targetlike isotopic production cross sections, which are calculated with GRAZING plus GEMINI model.