Nuclear rotation at the fission limit in Rf254

A ground-state rotational band in the fissile nucleus $^{254}\mathrm{Rf}$ was observed for the first time. Levels up to spin $14\ensuremath{\hbar}$ 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 $\ensuremath{\gamma}$-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 $\ensuremath{\gamma}$ 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 $\ensuremath{\gamma}$-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 $^{252}\mathrm{No}$.