One of the largest sets of collective excitations built on two-quasiparticle configurations in odd-odd nuclei of the proton-rich $A\approx 120$ mass region is reported in ${}^{118}\mathrm{Cs}$. Several new rotational bands and long-lived isomers have been identified. The $8^{+}$ bandhead of the $\pi h_{11/2}\otimes \nu h_{11/2}$ band is a short-lived isomer with a half-life in the nanosecond range, while the $7^{+}$ state below it is a long-lived isomer with a half-life of $T_{1/2}=0.55\left(6\right)\mu \mathrm{s}$. Two other long-lived isomers have been identified: a 66-keV transition detected at the MARA focal plane depopulates one of them, indicating a half-life in the microsecond range, while no depopulating transitions have been identified for the other, indicating a much longer half-life. Extensive particle number conserving cranked shell model calculations and alignment analysis have been employed to investigate the rich band structure of ${}^{118}\mathrm{Cs}$, which exhibits one of the most complete sets of two-quasiparticle configurations in nuclei close to the proton drip line.

• Received 12 May 2021
• Accepted 8 October 2021

DOI:https://doi.org/10.1103/PhysRevC.104.044325