Decay Properties ofI136

Abstract

${\mathrm{I}}^{136}$, produced from the slow neutron fission of uranium, has been studied with scintillation techniques. From the single-crystal (NaI) and gamma-gamma coincidence spectra, gamma rays were found at energies of 0.20, 0.27, 0.39, 0.46, 0.53, 0.71, 1.00, 1.321±0.006, 1.55, 1.72, 1.91, 2.25, 2.40, 2.63, 2.84, and 3.2 Mev. Also, from single-crystal (anthracene) and beta-gamma coincidence measurements, four beta-ray groups were observed with energies of 2.73, 4.23, 5.62, and 7.00 Mev, where the latter represents the ${\mathrm{I}}^{136}$-${\mathrm{Xe}}^{136}$ mass difference and is present in about 6% of the total beta-ray transitions. A partial decay scheme has been proposed, with energy levels in ${\mathrm{Xe}}^{136}$ at 1.32, 2.64, 2.84, 3.03, 3.23, 3.57, 3.74, and 4.20 Mev. The half-life of ${\mathrm{I}}^{136}$ was measured as 82.8±1.5 seconds. In the course of this investigation a source of 3.8-minute ${\mathrm{Xe}}^{137}$ was prepared, and was found to emit prominent gamma rays of 0.26 and 0.45 Mev.