A ground-state rotational band in the fissile nucleus ${}^{254}\mathrm{Rf}$ was observed for the first time. Levels up to spin $14\hslash$ and excitation energy of 1.56 MeV were observed. The ${}^{254}\mathrm{Rf}$ nuclei were produced using the ${}^{206}\mathrm{Pb}({}^{50}\mathrm{Ti},2n)$ fusion-evaporation reaction. It is the weakest reaction channel ever studied using in-beam $\gamma$-ray spectroscopic methods. The reaction products were separated from the beam in the Argonne gas-filled analyzer (AGFA). The ${}^{254}\mathrm{Rf}$ nuclei were implanted into a double-sided Si strip detector at the AGFA focal plane and tagged with subsequent ground-state spontaneous fission decays using temporal and spatial correlations. Prompt $\gamma$ rays in coincidence with the ${}^{254}\mathrm{Rf}$ recoils were detected in the Gammasphere array of Ge detectors. In order to identify the ground-state rotational band in ${}^{254}\mathrm{Rf}$, a method for identifying rotational bands in low statistics $\gamma$-ray spectra was developed. The deduced ${}^{254}\mathrm{Rf}$ kinematic moment of inertia is smaller compared to neighboring even-even nuclei. This is most likely associated with a slightly lower quadrupole deformation and stronger pairing correlations in ${}^{254}\mathrm{Rf}$. The behavior of the moment of inertia as a function of rotational frequency is similar to that of the lighter $N=150$ isotones ${}^{250}\mathrm{Fm}$ and ${}^{252}\mathrm{No}$.

• Received 19 January 2022
• Revised 5 April 2023
• Accepted 9 May 2023

DOI:https://doi.org/10.1103/PhysRevC.107.L061302