Radioactive Decay of 23-minSb131to Levels ofTe131

The levels of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}$ have been investigated by studying the $\gamma$ rays following the $\beta$ decay of 23-min ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ using Ge(Li) detectors. The ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ sources were produced by rapid separation of Sb from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ thermal-neutron-fission products. 60 $\gamma$ rays attributed to ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ decay have been observed and $\gamma -\gamma$ coincidence relationships have been obtained for the prominent lines. A level scheme has been constructed which incorporates 40 of these $\gamma$ transitions between 23 levels in ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}$. This level scheme is compared with the level structure of other odd-$A$ Te isotopes and is discussed within the framework of the pairing-plus-quadrupole model.