Recoil-isomer tagging has been used to characterize the states built upon an $I^{\pi }=8^{+}$ isomer in ${}^{142}\mathrm{Tb}$. High-spin states of the neutron-deficient nucleus ${}^{142}\mathrm{Tb}$ were populated using an ${}^{54}\mathrm{Fe}$ beam, accelerated onto a ${}^{92}\mathrm{Mo}$ target of thickness $~500\hspace{0.5em}\mu \mathrm{g}/{\mathrm{cm}}^2$ at energies of 245, 252, and 265 MeV using the K130 cyclotron at the University of Jyväskylä, Finland. Use of the JUROGAM target-position Ge-detector array coupled with the GREAT focal-plane spectrometer at the RITU gas-filled recoil separator has significantly increased the efficiency of the isomer-tagging technique. The rotational band built upon the $I^{\pi }=8^{+}$ isomeric state was established with isomer-tagged $\gamma \text{−}\gamma$ coincidence data and angular distributions were measured for some of the more intensely populated states. Two previously unobserved bands that bypass the isomer were also established. The new data have been interpreted within the framework of the cranked-shell model. The data show good agreement with the calculated triaxial nuclear shape with $\gamma =-{30}^{°}$ for the ${}^{142m2}\mathrm{Tb}$ isomeric state. The $B(M1)/B(E2)$ branching ratios, nuclear alignment, signature splitting, and reduced transition probability, $B(E1)$, of the isomeric state have been systematically compared with those of the neighboring nuclei. These comparisons give further evidence for the $\pi h_{11/2}\otimes \nu h_{11/2}$ configuration of the isomer.

• Received 24 November 2008

DOI:https://doi.org/10.1103/PhysRevC.79.024318