In the decay of the 4.2-min isomeric state in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Tb}$, $8\gamma$ rays are found to be associated with the deexcitation of levels in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Tb}$ and $25\gamma$ rays with that in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$. Experimental studies were made chiefly with Ge(Li)$\gamma$-ray detectors in singles and coincidence modes. Conversion-electron spectra were obtained with a Si(Li) spectrometer. The isomeric state, believed to be an $8^{+}$ state, is at 501.8 keV, and the isomeric transition is a 159.59-keV $E3\mathrm{}$ transition to a level at 342.2 keV. Other levels in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Tb}$ are proposed at 58.9, 65.1, and 106.7 keV. An alternative but less likely level scheme is also possible. The ground state ($2^{-}$) and levels at 58.9, 342.2, and 501.8 keV appear to be best described in terms of Nilsson states. The electron-capture decay of the 501.8-keV isomeric state is by an allowed unhindered transition ($log\mathrm{ft} 4.7$) which leads almost entirely to a level at 2394.5 keV in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$. The deexcitation of the latter level populates $6^{+}$ and $8^{+}$ members of the quasiground-state and quasi-$\beta$-vibrational bands. The quasirotational character of levels in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$ which has been proposed by Sakai and coworkers appears to be amply confirmed. A previously unreported level in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$ at 1861.7 keV ($5^{+}$) is proposed. In contrast to previous work, no $\alpha$-decay branch was observed.

• Received 19 October 1970

DOI:https://doi.org/10.1103/PhysRevC.3.1275