Saturation analysis as a test of statistical fission in heavy ion reactions

Evaporation residue and binary (fissionlike) cross sections are reported for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$+${}_{}{}^{120,122}{}_{}{}^{}\mathrm{Sn}$ at incident ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ energies between 330 and 456 MeV. The ${\sigma }_{\mathrm{ER}}$ are compared with results for the two additional entrance channels ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$+ ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$ and ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$+ ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ producing similar compound nuclei. Comparisons of $\frac{{\sigma }_{\mathrm{ER}}}{\pi {\lambda }^2}$ versus excitation energy (which tests the Bohr independence hypothesis) support the conclusion that the yields are limited by statistical fission decay. Similar results are shown for the entrance channels ${}_{}{}^{84,86}{}_{}{}^{}\mathrm{Kr}$+ ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+ ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$. It is shown that evaporation residue data of this type (where yields are limited by saturation in the fission channel) provide a good means of determining statistical fission parameters.