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

TL;DR

This study investigates how the breakup cross sections of weakly-bound 8Li nuclei depend on their binding energy, revealing that Coulomb breakup becomes more dominant as the binding energy decreases, especially in peripheral reactions.

Contribution

It provides a detailed analysis of Coulomb and nuclear breakup dependencies on binding energy, highlighting the increasing significance of Coulomb breakup at lower binding energies.

Findings

Breakup processes become more peripheral as binding energy decreases.

Coulomb breakup cross section increases more significantly than nuclear as binding energy decreases.

Nuclear absorption plays a minor role at small binding energies.

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.