Multinucleon transfer reactions in the ${}^{40}\mathrm{Ar}+{}^{208}\mathrm{Pb}$ system

We measured multinucleon transfer reactions in the ${}^{40}\mathrm{Ar}+{}^{208}\mathrm{Pb}$ system at an energy close to the Coulomb barrier, by employing the PRISMA magnetic spectrometer. We extracted differential and total cross sections of the different transfer channels, with a careful investigation of the total kinetic energy loss distributions. Comparisons between different systems having the same ${}^{208}\mathrm{Pb}$ target and with projectiles going from neutron-poor to neutron-rich nuclei, i.e., ${}^{40}\mathrm{Ca}$, ${}^{58}\mathrm{Ni}$, and ${}^{40}\mathrm{Ar}$, as well as between the data and GRAZING calculations have been carried out. The neutron-rich (stable) ${}^{40}\mathrm{Ar}$ beam allowed us to get access to the channels involving proton pickup, whose behavior in connection with the production of neutron-rich heavy partner has been outlined.

Figure 1

Matrix of range vs energy $E$ for the ${}^{40}\mathrm{Ar}+{}^{208}\mathrm{Pb}$ reaction at $E_{\mathrm{lab}}=6.4$ MeV/A and at ${\theta }_{\mathrm{lab}}={54}^{\circ }$. The range has been determined using the angle and position information of the ions entering the ionization chamber (IC), together with the different IC subanode information. The most intense band corresponds to Ar ions, with proton pickup and proton stripping channels visible above and below Ar.

Figure 2

Mass spectra for the transfer products measured in the ${}^{40}\mathrm{Ar}+{}^{208}\mathrm{Pb}$ reaction, spanning the range from $(+4p)$ to $(-4p)$ channels for even $Z$ isotopes for the three measured angles.

Figure 3

Experimental TKEL spectra for the indicated transfer channels at ${\theta }_{\mathrm{lab}}={54}^{\circ }$. The vertical dashed lines represent the ground-state $Q$ values. In the top row the mass spectra for each $Z$ are also depicted, with the red arrows indicating the pure proton transfer channels. The ${}^{40}\mathrm{Ar}$ peak has been scaled down by a factor 10 to better display the behavior of the transfer channels.

Figure 4

Wilczynski plots, kinetic energy $E$ in the laboratory system vs ${\theta }_{\mathrm{lab}}$, for selected channels in the ${}^{40}\mathrm{Ar}+{}^{208}\mathrm{Pb}$ reaction. The plots have been obtained by matching the measured events at the three PRISMA angular and magnetic settings.

Figure 5

Experimental (points) and GRAZING calculated (curves) angular distributions for the indicated transfer channels. The experimental distributions have been integrated over the full TKEL. The $\left(0n\right)$ channel corresponds to the elastic (+inelastic) channel, plotted as a ratio to the Rutherford cross section.

Figure 6

Experimental angular distributions of the $(+1n)$ and $(+1p+2n)$ channels integrated over the full TKEL range (black empty points) and integrated over the quasielastic part with the TKEL $\le 20$ MeV (red full points). The results of the GRAZING calculations are also plotted (curves).

Figure 7

Total experimental cross section for ${}^{40}\mathrm{Ar}$, ${}^{40}\mathrm{Ca}$, and ${}^{58}\mathrm{Ni}$ induced reactions on the ${}^{208}\mathrm{Pb}$ target, at beam energies $E_{\mathrm{lab}}=6.4$, 6.2, and 6 MeV/A, respectively (points), and the GRAZING calculations with (solid line) and without (dashed line) neutron evaporation.

Figure 8

Angle and energy integrated total cross section for ${}^{40}\mathrm{Ar}$, ${}^{40}\mathrm{Ca}$, and ${}^{58}\mathrm{Ni}$ projectiles on the ${}^{208}\mathrm{Pb}$ target, at energies $E_{\mathrm{lab}}=6.4$, 6.2, and 6 MeV/A, respectively. The cross section values of the elastic (+inelastic) channel, with $\mathrm{\Delta }N$ and $\mathrm{\Delta }Z=0$, have been scaled down by a factor 100 to better display the behavior of the transfer channels.