Dissipative effects in the formation of the {sup 156}Er compound nucleus

Light-charged particles were measured in coincidence with evaporation residues for {sup 12}C+{sup 144}Sm, {sup 35}Cl+{sup 121}Sb, and {sup 60}Ni+{sup 96}Zr reactions which populate the compound nucleus {sup 156}Er at the same excitation energy. The particle spectral shape for {sup 12}C+{sup 144}Sm is harder than the other two reactions. A one-body dissipation model predicts that the fusion times for the {sup 35}Cl- and {sup 60}Ni-induced reactions are similar and are about twice as long as that of the {sup 12}C-induced reaction. Statistical model calculations considering particle evaporation during compound nucleus formation successfully reproduce the particle spectra for all the reactions. {copyright} {ital 1997} {ital The American Physical Society}