ENTRANCE-CHANNEL EFFECTS IN QUASI-FISSION REACTIONS

The entrance-channel dependence of the distribution of reaction streng th has been studied for three systems, namely S-32 + W-182, Ti-48+ Er- 166, and Ni-60 + Sm-154, which all lead to the compound system Th-214 in complete fusion reactions. The cross sections for elastic/quasielas tic scattering, deeply inelastic, and fissionlike processes were measu red at beam energies of E(lab) = 166, 177, 222, 260 MeV for S-32+W-182 , E(lab) = 220, 240, 270, 298 MeV for Ti-48+ Er-166, and E(lab) = 339, 390, 421 MeV for Ni-60 + Sm-154, respectively. The maximum contributi on of complete-fusion fission processes to the fissionlike cross secti on is estimated on the basis of expected angle-mass correlations for s uch reactions. The results show a strong entrance-channel dependence a s predicted by the extra-push model.