Compound nucleus formation cross sections in lead-induced reactions

The formation of the compound nucleus in heavy-ion collisions is considered in two steps. The first step is related to the penetration of the ions through the capture barrier, the formation of the sticking nuclei in the capture well, and the transfer of kinetic energy of relative motion into the intrinsic energy of the sticking nuclei. The second step is associated with the compound-nucleus formation from the sticking nuclei in competition to the quasielastic scattering. The compound nucleus is preferably formed when the height of the compound nucleus formation barrier is substantially smaller than the height of the quasielastic barrier. This leads to the values of the capture and compound nucleus formation cross sections being close. In contrast, the formation of the compound nuclei is suppressed when the height of the compound-nucleus formation barrier is close to or larger than that of the quasielastic barrier. In this case, the capture cross sections are greater than the compound-nucleus formation cross sections. The suppression of the compound-nucleus formation is increased with the mass and charge of ions colliding with lead because the quasielastic barrier height obtained relative to the compound nucleus ground state is decreased with the mass and charge of ions colliding with lead and the role of the compound-nucleus formation barrier rises. The dependence of the compound-nucleus formation suppression on the shell-correction energy of the compound nucleus is shown. The available experimental data for 14 heavy-ion reactions induced by lead are well described in the model.