Near-barrier fusion and total reaction of a proton-rich projectile: ${}^3\mathrm{He}{+}^{58}$Ni

Evaporation protons from the fusion of the ${}^3\mathrm{He}{+}^{58}$Ni system were measured at three energies near but above the Coulomb barrier. The respective elastic scattering angular distribution was also determined for one of these energies. The fusion data, after being properly reduced to eliminate size and charge effects, are compared to the recently measured fusion excitation function for the proton-halo system ${}^8\mathrm{B}{+}^{58}$Ni. As a reference, fusion data for the ${}^{16}\mathrm{O}{+}^{58}$Ni system are also presented. With respect to this reference, the fusion cross sections for the proton-rich systems show an enhancement likely related to static effects. An excitation function for the respective total-reaction cross section was extracted from the measured elastic data along with additional data from the literature. Surprisingly, this excitation function follows the trend expected for weakly bound systems.

Figure 1

Typical proton spectrum (E${}_{\mathrm{lab}}=10.2$ MeV, ${\theta }_{\mathrm{lab}}={117}^{\circ }$) compared with a pace calculation. The latter was normalized to the total number of protons measured, $N=1956$.

Figure 2

Typical $\alpha$ spectrum ($E_{\mathrm{lab}}=11.5$ MeV) compared with a pace calculation. The $\Delta E$ detectors, optimized to resolve protons, stopped the lower energy $\alpha$ particles.

Figure 3

Differential proton cross sections measured (symbols) and corresponding pace calculations (lines).

Figure 4

Reduced fusion cross sections from the present work compared with data for other systems.

Figure 5

Elastic scattering angular distribution measured in the present work (symbols) and the results of an optical model calculation, described in the text (lines).

Figure 6

Elastic scattering angular distributions from the literature (symbols) and respective optical model calculations (lines) with the parameters given in Table . Data are from [30] (12 MeV), [31] (19.5 MeV), [32] (21.9 MeV), and [34] (24.1 MeV).

Figure 7

Total-reaction and fusion cross sections obtained in the present work (symbols). The meaning of the curves is explained in the text.