We report on the first $\beta$-decay data of ${}^{138}\text{Sb}$ to ${}^{138}\text{Te}$ isotopes beyond the doubly magic ${}^{132}\text{Sn}$. The parent nucleus was produced by the in-flight fission of a ${}^{238}\text{U}$ beam on a ${}^9\text{Be}$ target at 345 MeV per nucleon and measured at the BigRIPS separator of the Radioactive Isotope Beam Factory at RIKEN. By using advanced $\beta \text{−}\gamma$ spectroscopy techniques, the half-life and the tentative spin-parity of ${}^{138}\text{Sb}$ were measured to be 346(19) ms and $\left(3^{-}\right)$, respectively. In addition, we observed several low-lying non-yrast states in ${}^{138}\text{Te}$ for the first time. Our data allowed us to rearrange the positions of the first $2^{+}$ and $4^{+}$ states in this nucleus and to construct the level scheme of ${}^{138}\text{Te}$ in accordance with shell-model calculations. Additionally, we extend energy systematics of Te isotopes within neutron numbers 54 and 86.

• Received 16 September 2015

DOI:https://doi.org/10.1103/PhysRevC.92.044320