Fission Product Yields in Helium Ion-Induced Fission ofAu197,Pb204, andPb206Targets

Mass-yield curves have been measured radiochemically for fission of ${\mathrm{Au}}^{197}$, ${\mathrm{Pb}}^{204}$, and ${\mathrm{Pb}}^{206}$ target nuclei bombarded with 41.9-MeV helium ions. Fission is symmetric in all three cases, the data being satisfactorily represented by Gaussian-shaped curves with full widths at half-maximum of 30, 27, and 24 mass units, respectively. The widths at half-maximum, $W_{\frac{1}{2}}$, of a number of cases of fission in the symmetric mode are examined and it is shown that the widths appear to be correlated with the excitation energy $E_{\mathrm{S}.\mathrm{P}.\mathrm{}}^{}{}_{}{}^{*}$ which the fissioning nucleus possesses at the saddle point. Over the excitation energy interval 10-23 MeV the data follow the empirical expression $W_{\frac{1}{2}}=E_{\mathrm{S}.\mathrm{P}.\mathrm{}}^{}{}_{}{}^{*}+7\mathrm{}$.