Reactions of Alpha Particles with Iron-54 and Nickel-58

Abstract

The excitation functions for the ($\ensuremath{\alpha}, p$), ($\ensuremath{\alpha}, n$), ($\ensuremath{\alpha}, \mathrm{pn}$), ($\ensuremath{\alpha}, 2n$), ($\ensuremath{\alpha}, 2pn$), and ($\ensuremath{\alpha}, p2n$) reactions of ${\mathrm{Fe}}^{54}$ and the ($\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}p$), ($\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}n$), ($\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}\mathrm{pn}$), and ($\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}2n$) reactions of ${\mathrm{Ni}}^{58}$ have been determined for alpha-particle energies up to 40 Mev. A large preference for proton emission is observed. At the maxima in the excitation functions, these ratios were obtained: $\frac{\ensuremath{\sigma}(\ensuremath{\alpha}, p)}{\ensuremath{\sigma}(\ensuremath{\alpha}, n)}=3.1$; $\frac{\ensuremath{\sigma}(\ensuremath{\alpha}, pn)}{\ensuremath{\sigma}(\ensuremath{\alpha}, 2n)}=70$; $\frac{\ensuremath{\sigma}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}p)}{\ensuremath{\sigma}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}n)}=6$; $\frac{\ensuremath{\sigma}(\ensuremath{\alpha}, 2pn)}{\ensuremath{\sigma}(\ensuremath{\alpha}, p2n)}=6.3$ (at 40 Mev); and $\frac{\ensuremath{\sigma}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}pn)}{\ensuremath{\sigma}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}2n)}=140$ (at 40 Mev). These results are discussed in terms of the compound-nucleus model. A value of ${r}_{0}=1.7$ fermis is required to fit the low-energy portion of the observed "total" cross section with total reaction cross section calculated from continuum theory.