Coulomb-nuclear dynamics in the weakly-bound 8Li breakup

Abstract

A detailed study of total, Coulomb and nuclear breakup cross sections dependence on the projectile ground-state binding energy $\varepsilon_b$ is presented, by considering the $^8$Li+$^{12}$C and $^8$Li+$^{208}$Pb breakup reactions. To this end, apart from the experimental one-neutron separation energy of $^8$Li nucleus ($\varepsilon_b=2.03$~MeV), lower values of $\varepsilon_b$ down to $\varepsilon_b=0.01$~MeV, are also being considered. It is shown that all breakup processes become peripheral as $\varepsilon_b\to 0.01$ MeV, which is understood as due to the well-known large spacial extension of ground-state wave functions associated to weakly-bound projectiles. The Coulomb breakup cross section is found to be more strongly dependent on $\varepsilon_b$ than the nuclear breakup cross section, such that the Coulomb breakup becomes more significant as $\varepsilon_b$ decreases, even in a naturally nuclear-dominated reaction. This is mainly due to the long-range nature of the Coulomb forces, leading to a direct dependence of the Coulomb breakup on the electromagnetic transition matrix. It is also highlighted the fact that the nuclear absorption plays a minor role for small binding when the breakup becomes more peripheral.