Fusion versus breakup: observation of large fusion suppression for 9Be + 208Pb

Complete fusion excitation functions for ${}^{9}\mathrm{Be}{+}^{208}\mathrm{Pb}$ have been measured to high precision at near barrier energies. The experimental fusion barrier distribution extracted from these data allows reliable prediction of the expected complete fusion cross sections. However, the measured cross sections are only 68% of those predicted. The large cross sections observed for incomplete fusion products support the interpretation that this suppression of fusion is caused by ${}^{9}\mathrm{Be}$ breaking up into charged fragments before reaching the fusion barrier. Implications for the fusion of radioactive nuclei are discussed.