Fusion cross sections for the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ system have been measured by detecting the evaporation residues using a gas-ionization—surface-barrier $\Delta E-E$ detector at ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ bombarding energies of 35-55 MeV in 5 MeV steps. The ratios of the measured total fusion cross section to the total reaction cross section calculated using optical model parameters which fit the elastic scattering cross sections were found to be very small compared to the same results obtained from fusion studies of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ systems. This behavior is attributed to the high probability for breaking up of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ before the critical distance of fusion is reached.

• Received 5 July 1984

DOI:https://doi.org/10.1103/PhysRevC.30.1516