Pauli blocking effects in nα -nucleus-induced fusion reactions

Abstract

The hindrances in the $n\ensuremath{\alpha}$-nucleus-induced fusion reactions at deep subbarrier energies are investigated by using the coupled-channels model. Inspired by the microscopic Pauli-blocking effects of $\ensuremath{\alpha}$-cluster decay in radioactive nuclei, a Pauli blocking potential is constructed in the $n\ensuremath{\alpha}$-nucleus-induced fusion reactions by using a single folding procedure, in which the $n\ensuremath{\alpha}$ nuclei are assumed to be consisted of $\ensuremath{\alpha}$ particles. A shallow pocket is formed in the inner part of the potential between two colliding nuclei as compared to the one obtained from the double-folding potential with standard Michigan-3-Yukawa effective nucleon-nucleon interaction. The experimental fusion cross sections are described well for fusion systems $^{12}\mathrm{C}+^{198}\mathrm{Pt}$, $^{16}\mathrm{O}+^{208}\mathrm{Pb}$, $^{12}\mathrm{C}+^{30}\mathrm{Si}$, $^{24}\mathrm{Mg}+^{30}\mathrm{Si}$, and $^{28}\mathrm{Si}+^{30}\mathrm{Si}$. At deep subbarrier energies, it is found that this shallow pocket potential reduces the partial fusion cross sections and shields the contributions of high-angular-momentum partial waves to fusion cross sections. In addition, a detailed comparison of fusion processes with different projectiles $^{12}\mathrm{C}$, $^{24}\mathrm{Mg}$, and $^{28}\mathrm{Si}$ on the same target $^{30}\mathrm{Si}$ shows the hindrance effect is stronger for heavier projectiles.