Alpha particle production by molecular single-particle effect in reactions of ${}^9$Be just above the Coulomb barrier

Abstract

The $\hat{I}\pm$-particle production in the dissociation of ${}^9$Be on ${}^{209}$Bi and ${}^{64}$Zn at energies just above the Coulomb barrier is studied within the two-center shell model approach. The dissociation of ${}^9$Be on ${}^{209}$Bi 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 ${}^9$Be+${}^{64}$Zn, and this explains the absence of fusion suppression observed for this system. The polarisation of the energy level of the last neutron of ${}^9$Be and, therefore the existence of avoided crossings with that level, depends on the structure of the target.

5 pages, 4 figures