Above-barrier cross sections of fission and $\alpha$-active heavy reaction products were measured for the reactions of ${}^{10,11}\mathrm{B}$ with ${}^{209}\mathrm{Bi}$. Systematic analysis showed that the fission originates almost exclusively from complete fusion (CF). Existing measurements of above-barrier fusion products for the ${}^{30}\mathrm{Si}+{}^{186}\mathrm{W}$ reaction, assumed to proceed exclusively through CF, were extrapolated to the current systems using statistical model calculations. This extrapolation showed that the heavy reaction products from the ${}^{10,11}\mathrm{B}+{}^{209}\mathrm{Bi}$ reactions include substantial components from incomplete fusion as well as from CF. Compared with fusion calculations without breakup, the CF cross sections are suppressed by 15% for ${}^{10}\mathrm{B}$ and 7% for ${}^{11}\mathrm{B}$. A consistent and systematic variation of the suppression of CF for reactions of the weakly bound nuclei ${}^{6,7}\mathrm{Li}$, ${}^9\mathrm{Be}$, and ${}^{10,11}\mathrm{B}$ on targets of ${}^{208}\mathrm{Pb}$ and ${}^{209}\mathrm{Bi}$ is found as a function of the breakup threshold energy.

• Received 17 October 2008

DOI:https://doi.org/10.1103/PhysRevC.79.034605