The excitation function for production of ${}^{262}\mathrm{Bh}$ in the odd-Z-projectile reaction ${}^{208}\mathrm{Pb}$(${}^{55}\mathrm{Mn}$, $n)$ has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from ${}^{262}\mathrm{Bh}$ and 2 decay chains originating from ${}^{261}\mathrm{Bh}$ were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of ${540}_{-150}^{+180}$ pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than five times larger than that expected based on previously reported results for production of ${}^{262}\mathrm{Bh}$ in the analogous even-Z-projectile reaction ${}^{209}\mathrm{Bi}$(${}^{54}\mathrm{Cr}$, $n)$. Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the optimum energy rule proposed by Świątecki, Siwek-Wilczyńska, and Wilczyński.

• Received 18 May 2005

DOI:https://doi.org/10.1103/PhysRevC.73.014611