The levels of ${}_{}{}^{158}{}_{}{}^{}\mathrm{Dy}$ populated in the decay of 11-min ${}_{}{}^{158}{}_{}{}^{}\mathrm{Ho}_{}^g{}_{}{}^{}$ and 28-min ${}_{}{}^{158}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$ in equilibrium with 2.3-h ${}_{}{}^{158}{}_{}{}^{}\mathrm{Er}$ have been studied using singles Ge(Li) detectors, a Compton-suppression spectrometer and a Ge(Li)-Ge(Li) coincidence spectrometer. We firmly establish $K=0\mathrm{}$ one-phonon $\beta$-vibrational, $K=2\mathrm{}$ one-phonon $\gamma$-vibrational, $K=2\mathrm{}$ two-phonon ($\beta +\gamma$)-vibrational, and $K=4\mathrm{}$ two-quasineutron bands with new $\gamma$-ray singles, coincidence, and multipolarity evidence. Members of the $K=0, 1, 2, \mathrm{and} 3$ octupole vibrational bands are identified and compared to theoretical calculations. One-phonon octupole vibrational bands are proposed with the following assignments $I^{\pi }$(keV): $K=0\mathrm{}$: $1^{-}$(1608.0), $3^{-}$(1671.8), $5^{-}$(1818.7); $K=1\mathrm{}$: $1^{-}$(1441.7), $2^{-}$(1501.1), $3^{-}$(1513.6), $4^{-}$(1618.4), $5^{-}$(1634.5); $K=2\mathrm{}$: $2^{-}$(1371.7), $3^{-}$(1397.2), $4^{-}$(1518.5), $5^{-}$(1528.1); and $K=3\mathrm{}$: $3^{-}$(2409.6). A limiting value $\rho \ge 0.09$ has been measured for the monopole matrix element of the 990.6-keV $\beta$ vibration and a new low-lying $0^{+}$ state is reported at 1710.2 keV which may have collective character.

RADIOACTIVITY ${}_{}{}^{158}{}_{}{}^{}\mathrm{Ho}$ [from ${}_{}{}^{149}{}_{}{}^{}\mathrm{Sm}$ (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $3n$)(2.3-h, EC, ${\beta }^{+}$) ${}_{}{}^{158}{}_{}{}^{}\mathrm{Ho}$]; measured $E\gamma$, $I\gamma \gamma \gamma$ coin; deduced $log\mathrm{ft}$. ${}_{}{}^{158}{}_{}{}^{}\mathrm{Dy}$ deduced levels, $J$, $\pi$, ${\alpha }_K$, $\gamma$ multipolarities. Ge(Li) detectors, enriched targets.

• Received 16 March 1978

DOI:https://doi.org/10.1103/PhysRevC.18.383