Reactions of Alpha Particles with Tin-124

Abstract

The excitation functions for the ($\ensuremath{\alpha}, n$), ($\ensuremath{\alpha}, p$), ($\ensuremath{\alpha}, \mathrm{pn}$), ($\ensuremath{\alpha}, 2pn$), ($\ensuremath{\alpha}, 3n$), and ($\ensuremath{\alpha}, \ensuremath{\alpha}n$) reactions of ${\mathrm{Sn}}^{124}$ have been determined with alpha particles from 13-42 Mev of excitation energy. Cross sections for the production of the isomers of ${\mathrm{Te}}^{127}$, ${\mathrm{Sb}}^{126}$, ${\mathrm{Sn}}^{125}$, and ${\mathrm{Sn}}^{123}$ are also presented. Reactions in which there is only neutron emission predominate: the maximum cross sections for ($\ensuremath{\alpha}, n$) and ($\ensuremath{\alpha}, 3n$) (metastable state) are 0.161 barn at 18 Mev of excitation and 1.18 barn at 36 Mev, respectively. The ($\ensuremath{\alpha}, p$) has its maximum of 0.017 barn at 28 Mev, while the largest cross section obtained for the ($\ensuremath{\alpha}, \ensuremath{\alpha}n$) reaction is 0.056 barn at 42 Mev. The results are discussed in terms of the statistical theory of nuclear reactions. A satisfactory fit to the ($\ensuremath{\alpha}, n$) and ($\ensuremath{\alpha}, p$) data is obtained for ${r}_{0}=1.7$ fermis and $a=1.6$ ${\mathrm{Mev}}^{\ensuremath{-}1}$. However, both excitation functions exhibit high energy tails not predicted by the theory. An evaporation calculation using $a=1.6$ ${\mathrm{Mev}}^{\ensuremath{-}1}$ yields cross sections of proper magnitude for the ($\ensuremath{\alpha}, \ensuremath{\alpha}n$) reaction; but the shape of the experimental curve is not indicative of compound nuclear processes.