Energy levels in₉₈²⁵¹Cf populated in the α decay of₁₀₀²⁵⁵Fm

Gamma-ray spectra of a 20-h ²⁵⁵Fm source containing ∼1 mCi activity were measured with a 25% Ge detector and a low-energy photon spectrometer (LEPS). Gamma lines with intensities as low as 1.0×10^-6% per ²⁵⁵Fm α decay were observed. Gamma-gamma coincidence spectra of a ²⁵⁵Fm sample were measured with the GAMMASPHERE array. A comparison of the γ-ray spectrum gated by the Cf K_α x-ray peak with the γ-singles spectrum provided spins of the excited states in ²⁵¹Cf. The γ-ray data, in conjunction with previously measured ²⁵⁰Cf(d,p) reaction data, allowed us to characterize several single-particle and vibrational states above the N=152 subshell gap.