Inhibition of Fusion in Mass-Asymmetric Collisions

Comprehensive fission and evaporation residue measurements have been made for three reactions, all of which lead to the 216Ra compound nucleus, at energies from the Coulomb barriers upwards. The results show inhibition of fusion and the increasing presence of quasi-fission with decreasing mass-asymmetry of the projectile and target combination in the entrance channel. This work demonstrates a lower threshold for the inhibition of fusion and the onset of quasi-fission than previously expected.