We report on a set of in-beam studies of excited states in ${}^{250}\mathrm{Fm}$. We detected prompt γ rays by using the JUROSPHERE IV array and conversion electrons by using the SACRED spectrometer. Both devices were used in conjunction with the RITU gas-filled recoil separator located at the University of Jyväskylä. ${}^{250}\mathrm{Fm}$ nuclei were produced through the ${}^{204}\mathrm{Hg}$(${}^{48}\mathrm{Ca}$,$2n)$${}^{250}\mathrm{Fm}$ fusion-evaporation reaction. An experimental excitation function gave a maximum reaction cross section of (980 ± 160) nb at an energy of 209 MeV in the center of the target. Tagging techniques were employed, and a number of E2 transitions were observed that connected the ground-state band levels from spin $4^{+}$ up to ${18}^{+}$. The highly converted $4^{+}\to 2^{+}$ transition is observed only by use of conversion electron spectroscopy. The observed ground-state band transitions indicate a rotational structure. We deduce a quadrupole deformation parameter of ${\beta }_2=0.28$ ± 0.02. A low-energy background of apparent nuclear origin is observed in conversion electrons and postulated to arise from the decay of high-K bands. The half-life of ${}^{250}\mathrm{Fm}$ is measured to be 30.4 ± 1.5 min.

• Received 7 July 2005

DOI:https://doi.org/10.1103/PhysRevC.73.024308