Comparison of complementary reactions for the production ofBh261,262

Abstract

Two heavy-ion induced fusion reactions producing $^{261,262}\mathrm{Bh}$ were studied using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. An excitation function for the production of $^{262}\mathrm{Bh}$ via the reaction ${}^{209}\mathrm{Bi}({}^{54}\mathrm{Cr},n){}^{262}\mathrm{Bh}$ was measured with a maximum cross section from a fit to the data of 430 \ifmmode\pm\else\textpm\fi{} 110 pb observed at a compound nucleus excitation energy of 15.7 MeV. New data have been measured for the 1$n$ exit channel of the ${}^{208}\mathrm{Pb}({}^{55}\mathrm{Mn}, n){}^{262}\mathrm{Bh}$ reaction. We present an updated excitation function with an observed maximum cross section of $530\ifmmode\pm\else\textpm\fi{}100$ pb at a compound nucleus excitation energy of 14.1 MeV. Events corresponding to the 2$n$ exit channel for the ${}^{209}\mathrm{Bi}({}^{54}\mathrm{Cr},2n){}^{261}\mathrm{Bh}$ and ${}^{208}\mathrm{Pb}({}^{55}\mathrm{Mn},2n){}^{261}\mathrm{Bh}$ reactions were also observed and are presented as partial excitation functions. The measured decay properties correspond well with existing experimental data. We compare these experimental results to cross section predictions from a model by \ifmmode \acute{S}\else \'{S}\fi{}wia\ifmmode \mbox{\k{}}\else \k{}\fi{}tecki et al. and discuss entrance channel effects on the magnitude of 1$n$ cross sections.