Nuclear Data Sheets for A=240

Evaluated experimental data for radioactive decays and reactions for known nuclides (U, Np, Pu, Am, Cm, Bk, Cf) of A=240 are presented together with adopted values for level energies, gamma-ray energies, relative branching ratios and other nuclear properties. This revision was primarily motivated by the need for re-evaluation of absolute gamma-ray intensities from the E decay of Am-240 to (240)pu. These quantities are essential for determining precise and accurate cross-sections for the Am-241(n,2n)Am-240 reaction using fast neutrons (see e.g. Americium Workshop, Santa Fe, New Mexico, September 2007, 2008To06, 2007Ta01, 2006Pe14) and Am-241(gamma,n) reaction (see e.g. 2006Ri08). For U-240, the gamma-ray data have now become available. The data sets for Pu-244 alpha decay to U-240; Cm-244 alpha decay to Pu-240 and Cf-244 alpha decay to Cm-240 have been adapted from evaluations by 1998Ak04 and 2003Ak04. For Cm-244 decay, evaluation by 2006BeZL under the Decay Data Evaluation Project (DDEP) is also used. The gamma-ray data (energies and intensities) for Cm-240 decay are not considered (by the evaluators) as well established. Most detailed data are available only for Pu-240. Extensive data in the second potential well are available for this nuclide together with fission isomers and several superdeformed (SD) structures. For other nuclides spectroscopic data are rather sparse in the literature; especially for the following radioactive decays: The c decays of Cf-240, Bk-240 and Cm-240; multipolarities of gamma-ray transitions in Np-240 from U-240 beta(-) decay; gamma-ray transitions from Cf-244 a decay and %epsilon branch of Cf-244 decay; spins and parities of excited states in U-240 and multipolarities of associated gamma-ray transitions in U-240. This work supersedes earlier full evaluations of A=240 published by 2004Ch64, 1984Sh34, 1977Sc13, 1970Sc39; and an evaluation published in update mode by 1990Sh04.