The Radioactive Isotopes of Indium

Abstract

Although there are but two stable isotopes of indium whose mass numbers are 113 and 115, seven radioactive periods are shown to exist. Six of these whose half-life periods are 13 seconds, 72 seconds, 54 minutes, 2.3 hours, 4.1 hours and 50 days emit negative electrons, and one period of 20 minutes is radiopositive. By bombarding indium with slow neutrons, deuterons and very fast neutrons, and by bombarding cadmium with deuterons it is possible to assign with considerable confidence each period to a certain indium isotope. The conclusions are that the 54 minute and 13 second activities are both due to ${\mathrm{In}}^{116}$, the 4.1-hour and 50-day periods are both ${\mathrm{In}}^{114}$ and the 20-minute, 72-second and 2.3-hour periods are from isotopes of mass 111, 112, and 117, respectively. Beta-ray energy limits are approximately 2.15 Mev for the 50-day period and 1.75 Mev for the 20-minute positive period.