Decays of thef72isomersFeg53andFem53

The decays of 8.5-min ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}_{}^g{}_{}{}^{}$ and 2.5-min ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}_{}^m{}_{}{}^{}$ have been studied with a variety of $\gamma$ and ${\beta }^{+}$ detectors in many different singles and coincidence configurations. States in ${}_{}{}^{53}{}_{}{}^{}\mathrm{Mn}$ populated by ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}_{}^g{}_{}{}^{}$ decay were found to lie at 0 ($J^{\pi }={\frac{7}{2}}^{-}$), 377.9 (${\frac{5}{2}}^{-}$), 1288.0 (${\frac{3}{2}}^{-}$), 1619.9 (${\frac{9}{2}}^{-}$), 2273.5 (${\frac{5}{2}}^{-}$), 2685.6 (${\frac{7}{2}}^{-}$), 2946.6 (${\frac{9}{2}}^{-}$), 3126.7 (${\frac{9}{2}}^{-}, {\frac{7}{2}}^{-}, {\frac{5}{2}}^{-}$), and 3248.0 keV (${\left[\frac{9}{2}\right]}^{-}$). States in ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}$ populated by 3040.6-keV (${\frac{19}{2}}^{-}$) ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}_{}^m{}_{}{}^{}$ decay were confirmed at 0 (${\frac{7}{2}}^{-}$), 1328.1 (${\frac{9}{2}}^{-}$), and 2339.6 keV (${\frac{11}{2}}^{-}$). In addition, a 3040.6-keV $E6\mathrm{}$ and a 1712.6-keV $M5\mathrm{}$ transition were found to compete with the 701.1-keV $E4\mathrm{}$ isomeric transition in deexciting ${}_{}{}^{53}{}_{}{}^{}\mathrm{Fe}$, this being the first observation of such high multipolarities. The $E6\mathrm{}$ has an intensity of 6.0×${10}^{-4\mathrm{}}$ and the $M5\mathrm{}$ an intensity of 1.3×${10}^{-2\mathrm{}}$ relative to the $E4\mathrm{}$ transition. The $E4\mathrm{}$, $M5\mathrm{}$, and $E6\mathrm{}$ transitions are retarded by respective factors of 7.6, 4.2, and 4.3 with respect to single-particle estimates and by somewhat larger factors with respect to simple shell-model estimates.