States in $sup 126$Sb populated in the $beta$ decay of 10$sup 5$-yr $sup 126$Sn

The low-energy level structure of the odd-odd nucleus $sup 126$Sb has been investigated by studying the radioactive decay of 10$sup 5$-yr $sup 126$Sn, by using Ge(Li) and Si(Li) detectors. From conversion-electron and $gamma$-ray singles data, $gamma$-$gamma$ and $gamma$-e$sup -$ prompt and delayed coincidence measurements, and complementary $gamma$-ray energy and intensity balance arguments, a decay scheme for $sup 126$Sn has been deduced which accommodates all of the observed $gamma$-ray transitions. The energies (keV), spins, and parities of the levels established in $sup 126$Sb are as follows: 0.0 [8$sup -$], 17.7 [5$sup +$], 40.4 [3$sup -$], 83.1 [4$sup -$, (3$sup -$)], 104.7 [3$sup +$], and 128.0 [2$sup +$]. The respective half-lives of these six states are: 12.4 day, 19.0 min, approx. =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. (AIP)