The influence of the fission barrier on the mass distribution in reactions with symmetric fragmentation

The mass distributions of reaction products with symmetric fragmentation resulting from the bombardment of 144Sm, 165Ho, 175Lu, 176Hf, 181Ta, and 208Pb with 40Ar projectiles have been studied. The incident energies were chosen to populate nearly the same angular momentum range of the composite system while the nuclear temperature varies only weakly. The reaction products were identified by their energy and time of flight using a solid state detector placed at 600. The width of the mass distribution was found to increase by nearly a factor of two as the liquid drop fission barrier of the different compound nuclei decreases from 11 to 2.2 MeV. For all systems, the survival of evaporation residues proves that compound fission contributes to the observed symmetric reaction component. (orig.)