Cross Sections for Formation of the Isomeric Pair ${\mathrm{In}}^{117}$ and ${\mathrm{In}}^{117m}$ in the ${\mathrm{Sn}}^{120}(p,\alpha )$ Reaction

The excitation functions and yield ratio ($\frac{{\sigma }_g}{{\sigma }_m}$) for the isomeric pair ${\mathrm{In}}^{117}$ and ${\mathrm{In}}^{117m}$ produced from ${\mathrm{Sn}}^{120}$ by the ($p,\alpha$) reaction were measured for energies from threshold to 22 MeV. The yield ratio vs energy is large at low energies, drops to a minimum at 13 MeV, and then rises linearly to 22 MeV. The measured half-lives of the excited and ground state of ${\mathrm{In}}^{117}$ were found to be 117.5±1.0 and 44.6±0.6 min, respectively.