Radioactive sources of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Lu}$ were produced in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ bombardments of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$. A helium-jet capillary system was used to transport product nuclei to a shielded area suitable for $\gamma$-ray counting. Both singles and coincidence measurements were made. The half-life of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Lu}$ was found to be 3.17 ± 0.03 min, in agreement with earlier measurements. This state in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Lu}$ is thought to have a low spin, most probably a value of 2; there is also some evidence for the existence of a high-spin isomer, possibly of shorter half-life, based on weak population of high-spin states in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}$. Fifteen levels were placed in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}$, 12 of them previously unknown. The $2^{+}$ and $3^{+}$ members of the $\gamma$ vibrational band are located at 863.9 and 1004.2 keV; there are also candidates for the $4^{+}$ and $5^{+}$ members. An even-odd shift in the $\gamma$ band, both in level energies and mixing parameters, is observed with a magnitude greater than in the previously studied ${}_{}{}^{166,168}{}_{}{}^{}\mathrm{Yb}$ cases. A $K=0\mathrm{}$ $2^{+}$ level is placed at 1073.8 keV, and its effect on the $\gamma$ band is discussed. From an analysis of the population trends of levels in ${}_{}{}^{164,166,168}{}_{}{}^{}\mathrm{Yb}$ from Lu decays, we make arguments concerning the available proton and neutron Nilsson orbitals.

[RADIOACTIVITY ${}_{}{}^{164}{}_{}{}^{}\mathrm{Lu}$ [from ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},5n)$, $E=79\mathrm{}$ MeV]. Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$ coin. Deduced ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}$ levels, $J$, $\pi$, $log\mathrm{ft}$.]

• Received 25 March 1977

DOI:https://doi.org/10.1103/PhysRevC.16.384