The excitation function for quasielastic scattering of the weakly bound projectile ${}^6\mathrm{Li}$ on a ${}^{159}\mathrm{Tb}$ target, at large backward angle, has been measured at energies around the Coulomb barrier. The corresponding quasielastic barrier distribution has been extracted from the experimental cross sections, both including and excluding the $\alpha$ particles produced in the reaction. The quasielastic scattering cross sections, excluding the $\alpha$ particles, have been analyzed in the framework of coupled channels calculations. The centroid of the quasielastic barrier distribution, including the $\alpha$ particles, is found to shift towards higher energy relative to the centroid of the fusion barrier distribution for the system. This has been attributed to the low $\alpha$-breakup threshold of the nucleus ${}^6\mathrm{Li}$.

• Received 8 April 2021
• Revised 25 June 2021
• Accepted 23 August 2021

DOI:https://doi.org/10.1103/PhysRevC.104.034620