Coulomb-nuclear dynamics in the breakup of the weakly bound Li8 nucleus

Abstract

A detailed study of total, Coulomb, and nuclear breakup cross sections dependence on the projectile ground-state binding energy ${\ensuremath{\varepsilon}}_{b}$ is presented by considering the $^{8}\mathrm{Li}+^{12}\mathrm{C}$ and $^{8}\mathrm{Li}+^{208}\mathrm{Pb}$ breakup reactions. To this end, apart from the experimental one-neutron separation energy of $^{8}\mathrm{Li}$ nucleus $({\ensuremath{\varepsilon}}_{b}=2.03\phantom{\rule{0.16em}{0ex}}\mathrm{MeV})$, lower values of ${\ensuremath{\varepsilon}}_{b}$ down to ${\ensuremath{\varepsilon}}_{b}=0.01\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, are also being considered. It is shown that all breakup processes become peripheral as ${\ensuremath{\varepsilon}}_{b}\ensuremath{\rightarrow}0.01\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, 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 ${\ensuremath{\varepsilon}}_{b}$ than the nuclear breakup cross section, such that the Coulomb breakup becomes more significant as ${\ensuremath{\varepsilon}}_{b}$ 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.