Direct and compound-nucleus reaction mechanisms in the 7Be + 58Ni system at near-barrier energies

Abstract

The energy and angular distributions of 3He and 4He ions produced in the 7Be+58Ni reaction at a bombarding energy of 22 MeV have been measured for the first time. The yield of the heavier helium isotope was four to five times more abundant than that of its lighter counterpart, ruling out the possibility that in this energy range the 7Be reaction dynamics is dominated by the exclusive breakup process 7Be → 3He + 4He (Sα = 1.586 MeV). Extensive kinematic and theoretical calculations suggest that the 3He ions mostly originate from the 4He-stripping process and the 4He production is mainly triggered by the fusion-evaporation channel. The role played by the breakup, 3He-stripping, 1n-stripping, and 1n-pickup processes is also discussed.