Near-Barrier Fusion of the ${}^8\mathbf{B}+{}^{58}\mathrm{Ni}$ Proton-Halo System

Fusion cross sections were measured for the exotic proton-halo nucleus ${}^8\mathrm{B}$ incident on a ${}^{58}\mathrm{Ni}$ target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.

Figure 1

Typical proton spectrum ($E_{\mathrm{lab}}=22.4\mathrm{MeV}$) compared with a PACE calculation. Data from all four telescopes have been summed and background corrections discussed in the text have been made.

Figure 2

Fusion excitation function ${\sigma }_{\mathrm{fus}}$ obtained in the present work. Data previously reported for the total reaction cross section ${\sigma }_R$ [7] and the breakup cross section ${\sigma }_{\mathrm{bu}}$ [6, 7] are also shown. The horizontal error bars illustrate the energy averaging interval corresponding to the beam energy resolution (energy straggling effects are negligible). The dot-dashed curve is a Wong-model fit to the fusion data, yielding the indicated barrier parameters. The remaining curves were obtained from CDCC calculations performed with the code FRESCO.