In-beam gamma ray and conversion electron study of 250Fm

We report on a set of in-beam studies of excited states in Fm-250. We detected prompt gamma 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 Jyvaskyla. Fm-250 nuclei were produced through the Hg-204(Ca-48,2n)Fm-250 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(+)-> 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 Fm-250 is measured to be 30.4 +/- 1.5 min.