Prompt and delayed $\gamma$-ray cascades in doubly magic ${}^{132}\mathrm{Sn}$ and its neighbor ${}^{131}\mathrm{Sn}$ have been studied at Gammasphere using a ${}^{248}\mathrm{Cm}$ fission source. Isotopic assignments of unknown $\gamma$ rays were based on coincidences with known transitions in $A=112\mathrm{}–116\mathrm{Pd}$ fission partners. The yrast level spectra of both tin nuclei are interpreted using empirical nucleon-nucleon interactions from the ${}^{132}\mathrm{Sn}$ and ${}^{208}\mathrm{Pb}$ regions. Results include identification of the $\left(\nu f_{7/2}{h}_{11/2}^{-1\mathrm{}}\right)9^{+}$ aligned state in ${}^{132}\mathrm{Sn}$ and of extensive $\left(\nu f_{7/2}{h}_{11/2}^{-2\mathrm{}}\right)$, $\left(\nu f_{7/2}{d}_{3/2}^{-1\mathrm{}}{h}_{11/2}^{-1\mathrm{}}\right)$ and $(\nu h_{11/2}^{-1\mathrm{}}\times 3^{-})$ multiplets in ${}^{131}\mathrm{Sn}$. The previously reported ${\beta }^{-}$ decay of an unusual ${}^{131}\mathrm{In}$ high-spin isomer to levels in ${}^{131}\mathrm{Sn}$ is also elucidated.

• Received 7 March 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.062502