Nuclear Data Sheets for A=254☆

Spectroscopic data for known A=254 nuclides (U, Cf, Es, Fm, Md, No, Lr and Rf) have been updated and re-evaluated, superseding the data presented in the previous evaluation 2005Bh12 published by A. Bhagwat, N.J. Thompson and J.K. Tuli. With the exception of the ²⁵⁴No nuclide, excited-state data for A=254 nuclei are largely unknown. The decay of the 184−μs isomer in ²⁵⁴No has been studied in two independent experiments, results of which differ significantly, thus precluding adoption of any one particular decay scheme. Only the features that are consistent in these studies are included in the Adopted dataset, whereas independent decay schemes are presented in separate datasets. Information is also presented here for possible production of the ²⁵⁴U nuclide in a study (1960Di03) of debris of the first large-scale thermonuclear test (Ivy Mike) of November 1, 1952 in the Pacific Ocean.