The low-energy level structure of the odd-odd nucleus ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sb}$ has been investigated by studying the radioactive decay of ${10}^5$-yr ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sn}$, using Ge(Li) and Si(Li) detectors. Based on conversion-electron and $\gamma$-ray singles data, $\gamma -\gamma$ and $\gamma -e^{-}$ prompt and delayed coincidence measurements, and complementary $\gamma$-ray energy and intensity balance arguments, a decay scheme for ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sn}$ has been deduced which accommodates all of the observed $\gamma$-ray transitions. The energies (keV), spins, and parities of the levels established in ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sb}$ are as follows: 0.0 [$8^{-}$], 17.7 [$5^{+}$], 40.4 [$3^{-}$], 83.1 [$4^{-}$, ($3^{-}$)], 104.7 [$3^{+}$], and 128.0 [$2^{+}$]. The respective half-lives of these six states are: 12.4 day, 19.0 min, ≅11 s, 5.1 ns, 553 ns, and 78.0 ns, the latter four values having been determined in the present investigation. The level assignments are discussed within the framework of the single-particle shell model and in relation to the proposed assignments of low-lying energy levels of neighboring odd-odd antimony isotopes.

RADIOACTIVITY ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sn}$ [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}\mathrm{}(n,f)\mathrm{}$]; measured $E_{\gamma }$, $I_{\gamma }$, $I_{\mathrm{ce}}$, $\gamma -\gamma$, $\beta -\gamma$, and $e-\gamma$ coin, level $T_{\frac{1}{2}}\text{'}\mathrm{s}$; deduced ICC, $\gamma$ multipolarities, ${}_{}{}^{126}{}_{}{}^{}\mathrm{Sb}$ levels, $J$, $\pi$; calculated $\gamma$-hindrance factors. Ge(Li), Si(Li) detectors; mass-separated source.

• Received 8 September 1975

DOI:https://doi.org/10.1103/PhysRevC.13.387