Studies of Nuclear Structure and Decay Properties of Actinide Nuclei

The identification of single-particle states in heavy actinide nuclei by means of studying their decay schemes plays a seminal role in understanding the structure of the heaviest elements and testing the predictive power of modern theoretical models. The heaviest odd-mass nuclides available in sufficient quantity for detailed decay spectroscopic studies are 20-h 255 Fm(for neutrons) and 20-d 253Es(for protons). Decay spectra of these isotopes, together with those for the odd-odd 276-d 254Es nuclide, were measured using a variety of α-particle and γ-ray spectroscopy techniques. Well-defined decay data are also essential pre-requisites for the detection and accurate characterization of fissile radionuclides. The parameters of greatest relevance include actinide half-lives, branching fractions, and α-particle and γ-ray energies and emission probabilities. Their quantification to good accuracy provides the means of monitoring their presence, behavior and transport in nuclear facilities as well as any clandestine movement and usage. As a consequence of recommendations made at recent IAEA research coordination meetings on ''Updated Decay Data Library for Actinides,'' measurements were undertaken to determine specific decay data of the more inadequately defined radionuclides.