The decay properties of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Lu}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tm}$, and of the α-decay daughters ${}_{}{}^{151}{}_{}{}^{}\mathrm{Er}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}$ were investigated following the on-line mass separation of A=155 nuclides produced in ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$ irradiations of ${}_{}{}^{95}{}_{}{}^{}\mathrm{Mo}$. In the study, the half-life of the low-spin isomer in ${}_{}{}^{155}{}_{}{}^{}\mathrm{Lu}$ was measured to be 140±20 ms, the β-decay branch of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Yb}$ was identified by observing daughter γ rays and Tm K x rays, and the existence in ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tm}$ of an ${\mathit{s}}_{1/2}$ isomer (${\mathit{T}}_{1/2}$=44±4 s), in addition to the ${\mathit{h}}_{11/2}$ ground state (${\mathit{T}}_{1/2}$=21.6±0.2 s) was established. Schemes for the β decays of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tm}$, and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Er}$ are proposed. New information on ${}_{}{}^{151}{}_{}{}^{}\mathrm{Er}$ decay establishes the ${\mathit{s}}_{1/2}$ isomer in ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}$ to be 41.1±0.2 keV above the ${\mathit{h}}_{11/2}$ ground state. Also, branchings of 90±5, 28±7, and ${80}_{\mathrm{-}20}^{+15\mathrm{}}$% were determined for the α decays of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}$, and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}_{}^{\mathit{m}}{}_{}{}^{}$, respectively.

• Received 19 June 1991

DOI:https://doi.org/10.1103/PhysRevC.44.1868