A delayed, 76.5-keV transition has been observed in coincidence with ${}^{97}$Rb at the Lohengrin mass spectrometer via $\gamma$-ray and conversion-electron spectroscopy. The multipolarity of the delayed transition was determined to be $E1$ and its measured half-life is 5.1(4) $\mu$s. Comparisons with the results of Hartree-Fock-Bogoliubov and quasiparticle-rotor model calculations allow a spin and parity of ${(1/2,3/2)}^{-}$ to be assigned to this state. The isomer is likely to be one of the low-lying prolate-deformed $3/2^{-}\left[312\right]$, or oblate-deformed $1/2^{-}\left[321\right]$, $3/2^{-}\left[321\right]$ quasiparticle excitations. A new decay branch of the ($9/2^{+}$), 830.8-keV isomer of ${}^{97}$Sr has also been observed in the same experiment, allowing a spin of ${(5/2)}^{+}$ to be assigned to the 522.5-keV state. This level is likely to have a high-seniority spherical configuration.

• Received 12 November 2012

DOI:https://doi.org/10.1103/PhysRevC.87.064317