Alpha particle production by molecular single-particle effect in reactions of [formula omitted] just above the Coulomb barrier

Abstract

The α-particle production in the dissociation of 9Be on 209Bi and 64Zn at energies just above the Coulomb barrier is studied within the two-center shell model approach. The dissociation of 9Be on 209Bi is caused by a molecular single-particle effect (Landau–Zener mechanism) before the nuclei reach the Coulomb barrier. Molecular single-particle effects do not occur at that stage of the collision for 9Be+64Zn, and this explains the absence of fusion suppression observed for this system. The polarisation of the energy level of the last neutron of 9Be and, therefore the existence of avoided crossings with that level, depends on the structure of the target.