Production of neutron-rich transcalifornium nuclei in ${}^{238}\mathrm{U}$-induced transfer reactions

In order to produce more unknown neutron-rich transcalifornium nuclei, the collisions of ${}^{238}\mathrm{U}$ with the targets ${}^{248}\mathrm{Cm}$, ${}^{249}\mathrm{Cf}$, and ${}^{250}\mathrm{Cm}$ are investigated within the framework of the dinuclear system model. The production cross sections of unknown neutron-rich nuclei with $Z=99–104$ in these reactions are predicted. The influences of $N/Z$ ratios and charge numbers of the targets on the production cross sections are studied. It is found that high $N/Z$ ratios of ${}^{248}\mathrm{Cm}$ and ${}^{250}\mathrm{Cm}$ targets enhance the production cross sections of neutron-rich transcalifornium nuclei. However, due to high charge number of the target ${}^{249}\mathrm{Cf}$ the predicted production cross sections of unknown neutron-rich nuclei with $Z=104$ in the reaction ${}^{238}\mathrm{U}+{}^{249}\mathrm{Cf}$ are higher than those in ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$. We also have studied the entrance angular momentum effects on production probabilities of transfer products in the reaction ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$. It is found that the formation probabilities of the final neutron-rich products increase first and then decrease with the increasing $J$.

Figure 1

Comparison of calculated cross sections for the formation of isotopes of the elements einsteinium (solid lines), fermium (dashed lines), and mendelevium (dash-dotted lines) with the experimental data [6]. The thin and thick lines are distributions of primary and final fragments, respectively. The incident energy $E_{\mathrm{c}.\mathrm{m}.}=800$ MeV.

Figure 2

Cross sections for synthesizing isotopes of the elements with $Z=99–104$ in transfer reactions ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$ (dash lines), ${}^{238}\mathrm{U}+{}^{249}\mathrm{Cf}$ (solid lines), and ${}^{238}\mathrm{U}+{}^{250}\mathrm{Cm}$ (dash-dotted lines). The incident energy $E_{\mathrm{c}.\mathrm{m}.}=1.1\times V_{\mathrm{CN}}$. $V_{\mathrm{CN}}$ is the interaction potential at the touching point (tip-tip). The circles denote the unknown nuclei.

Figure 3

$N/Z$ ratios of the unknown neutron-rich nuclei denoted in Fig. 2.

Figure 4

The probability distributions of the production of einsteinium isotopes in the transfer reactions ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$ at different incident angular momentums. The incident energy $E_{\mathrm{c}.\mathrm{m}.}=1.1\times V_{\mathrm{CN}}$. Thick and thin lines denote the probability distributions of final and primary fragments, respectively. The circles denote the unknown neutron-rich isotopes.

Figure 5

The excitation energies of the primary products with $Z=99$ in the reaction ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$ at different incident angular momentums. The incident energy $E_{\mathrm{c}.\mathrm{m}.}=1.1\times V_{\mathrm{CN}}$.