The level structure of ${}_{}{}^{133}{}_{}{}^{}\mathrm{I}$ excited in the $\beta$ decay of 54-min ${}_{}{}^{133m}{}_{}{}^{}\mathrm{Te}$ and 12-min ${}_{}{}^{133g}{}_{}{}^{}\mathrm{Te}$ has been studied using Ge(Li) $\gamma$-ray spectrometers in conjunction with a 4096-channel pulse-height analyzer. Coincidence measurements were carried out using two NaI(Tl) spectrometers and a 256×256-channel coincidence analyzer. Sources of ${}_{}{}^{133g}{}_{}{}^{}\mathrm{Te}$ were made, free of ${}_{}{}^{133m}{}_{}{}^{}\mathrm{Te}$, by an isomeric separation method. All 14 transitions associated with the decay of ${}_{}{}^{133g}{}_{}{}^{}\mathrm{Te}$ have been placed in a consistent decay scheme on the basis of the coincidence measurements, relative intensities, and energy combinations. Levels in ${}_{}{}^{133}{}_{}{}^{}\mathrm{I}$ populated from ${}_{}{}^{133g}{}_{}{}^{}\mathrm{Te}$ occur at 311.99, 719.65, 786.77, 1312.8, 1333.23, 1564.1, 1717.65, and 2193.5 keV. From a $\beta$ endpoint measurement using an anthracene detector, a total disintegration energy for ${}_{}{}^{133g}{}_{}{}^{}\mathrm{Te}$ of 2.96 MeV was obtained. $\mathrm{Log}\mathrm{ft}$ values and $\beta$ branching ratios have been calculated from the $\gamma$-ray intensities. The decay scheme of ${}_{}{}^{133m}{}_{}{}^{}\mathrm{Te}$ is quite complex, with 63 additional $\gamma$ rays having been identified with this activity. Of these, only three have been unambiguously placed in the decay scheme. They require the existence of additional levels in ${}_{}{}^{133}{}_{}{}^{}\mathrm{I}$ at 912.58, 1560.0, and 1776.5 keV.

• Received 21 March 1968

DOI:https://doi.org/10.1103/PhysRev.172.1253