Proton Activation of Indium and Cadmium

Abstract

Indium activated by 7.2-Mev protons exhibits two activities, one due to ${\mathrm{In}}^{115*}$ and one due to ${\mathrm{Sn}}^{113}$. The other two activities previously reported have been shown to be due to impurities. ${\mathrm{Sn}}^{113}$ has a half-life of about 100 days and decays by $K$-electron capture emitting In $K$ x-rays. An active In of 105±10 min. half-life with a $\gamma$-ray of 0.39 Mev has been chemically separated from an aged ${\mathrm{Sn}}^{113}$ sample. An exactly similar In has been formed by proton bombardment of Cd which suggests the assignment of this activity to an excited state of stable ${\mathrm{In}}^{113}$. The absence of Cd $K$ x-rays indicates that ${\mathrm{In}}^{113*}$ decays to ${\mathrm{In}}^{113}$ with the emission of the 0.39-Mev $\gamma$-ray. In addition bombarded Cd shows the expected In isotopes ${\mathrm{In}}^{111}$ 20 min. (+), ${\mathrm{In}}^{114}$ 48 days (-) and ${\mathrm{In}}^{116}$ 54 min. (-). A positron emitter of 65±5 min. half-life with a maximum positron energy of 1.6±0.3 Mev is found and tentatively assigned to ${\mathrm{In}}^{110}$. Activities of 72 sec. (-) and 2.7±0.2 days (-) the latter accompanied by $\gamma$-rays of 170 and 250 kev are ascribed to isomeric states of ${\mathrm{In}}^{112}$.