A level scheme for ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ is proposed taking into account the gamma-ray energy and intensity and the gamma-gamma coincidences obtained in the decay of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sn}$. The samples were obtained using on-line mass-separation techniques applied to ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ thermal-neutron fission products. The half-life of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sn}$ was measured to be 61±1 s. The level structure in ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ is compared with a particle-core coupling calculation using a quadrupole protonneutron interaction.

RADIOACTIVITY ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sn}$ (from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$($n_{\mathrm{th}}$,$f$); measured $E_{\gamma }$, $I_{\gamma }$,$\gamma -\gamma$ coincidences and $T_{\frac{1}{2}}$ of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sn}$, Ge(Li), and Ge intrinsic detectors; ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ deduced levels and $\beta$ branches. Mass-separated ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ activities.

• Received 5 January 1981

DOI:https://doi.org/10.1103/PhysRevC.24.2227