Reaction cross sections for ${}^8\mathrm{B}$, ${}^7\mathrm{Be}$, and ${}^6\mathrm{Li}+{}^{58}\mathrm{Ni}$ near the Coulomb barrier: Proton-halo effects

Elastic scattering of ${}^8\mathrm{B}$, ${}^7\mathrm{Be}$, and ${}^6\mathrm{Li}$ on a ${}^{58}\mathrm{Ni}$ target has been measured at energies near the Coulomb barrier. Optical-model fits were made to the experimental angular distributions, and total reaction cross sections were deduced. A comparison with other systems provides striking evidence for proton-halo effects on ${}^8\mathrm{B}$ reactions. As opposed to the situation for the neutron-halo nucleus ${}^6\mathrm{He}$, for which particle transfer dominates, the “extra” cross section observed for ${}^8\mathrm{B}$ appears to result entirely from projectile breakup.

Figure 1

One-dimensional spectrum obtained with a PSD. The elastic scattering peaks for ${}^8\mathrm{B}$, ${}^7\mathrm{Be}$, and ${}^6\mathrm{Li}$ are indicated.

Figure 2

Elastic scattering angular distributions for (${}^8\mathrm{B}$, ${}^7\mathrm{Be}$, ${}^6\mathrm{Li}$) $+$ ${}^{58}\mathrm{Ni}$ at the five energies indicated. If not shown, error bars (purely statistical) are smaller than the size of the symbol. The curves correspond to optical model calculations with the potentials of Tables and .

Figure 3

Total reaction and breakup cross sections for ${}^8\mathrm{B}+{}^{58}\mathrm{Ni}$. The various curves represent calculations that are discussed in the text.

Figure 4

Reduced cross sections from the present work compared with other data. The curves are to guide the eye.