Excitation energy dependence of the cross sections of the reactions ${}^{208}{\mathrm{Pb}}_{126}{(}^{50}{\mathrm{Ti}}_{28}{,1n)}^{257}{\mathrm{Rf}}_{153}$ and ${}^{208}{\mathrm{Pb}}_{126}{(}^{58}{\mathrm{Fe}}_{32}{,1n)}^{265}{\mathrm{Hs}}_{157}$ is calculated and compared with the experimental data measured at GSI-Darmstadt. Such a dependence is also calculated for the reaction ${}^{208}{\mathrm{Pb}}_{126}{(}^{86}{\mathrm{Kr}}_{50}{,1n)}^{293}{118}_{175}$ reported recently by the Berkeley group, and for reactions which may lead to the synthesis of element 119 and production of its odd-$Z$ descendants. Recommendations for future experiments based on the present study are presented.

• Received 13 July 1999

DOI:https://doi.org/10.1103/PhysRevC.61.011601