High Energy Gamma-Gamma Cross Section ofIn115

Several photonuclear reactions induced in indium by the x-rays from a 25-Mev betatron have been measured. Special attention has been given to the reaction ${\mathrm{In}}^{115}(\gamma , {\gamma }^{\prime }){\mathrm{In}}^{115*}$. Applying proper corrections, it was found that this reaction has a shape similar to the shape found in the usual photonuclear reactions. This experiment shows that 1 in 7 de-excitations of an excited indium nucleus decays by $\gamma$-emission. The ($\gamma , n$) reaction in ${\mathrm{In}}^{115}$ has been measured and was found to have 0.42 Mev-barn for the integrated cross section, in good agreement with theoretical predictions. The ratio of the cross sections for production of the isomeric and ground states of ${\mathrm{In}}^{114}$ has also been studied. It was found that transitions to the isomeric state of ${\mathrm{In}}^{114}$ are highly favored, as would be expected from an analysis of the spin changes involved. The cross section for the reaction ${\mathrm{In}}^{115}(\gamma , 2n){\mathrm{In}}^{113*}$ has been measured and the ratio of this cross section to the ($\gamma , n$) reaction is compared with that predicted by statistical theory.