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DOE OSTI2019

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 {sup 254}No nuclide, excited-state data for A=254 nuclei are largely unknown. The decay of the 184−μs isomer in {sup 254}No 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 {sup 254}U nuclide in a study (1960Di03) of debris of the first large-scale thermonuclear test (Ivy Mike) of November 1, 1952 in the Pacific Ocean.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2020

Separation and Purification of Berkelium-249 and Einsteinium-254

Berkelium-249 ( 249 Bk) and einsteinium-254 ( 254 Es) are isotopes of great importance for the investigation of berkelium and einsteinium chemical properties and super heavy element research. Therefore, it is necessary to be able to isolate acceptable, pure quantities of both isotopes to further research capabilities. These isotopes, along with californium-252 ( 252 Cf), are synthesized through the irradiation of mixed-curium targets in the High Flux Isotope Reactor (HFIR), which has the highest continuous thermal neutron flux in the world. Once irradiated, the targets are transferred to the Radiochemical Engineering Development Center for further chemical processing and final purification to separate 249 Bk and 254 Es from the remainder of isotopes present. Several methods of separation, such as the Berkex batch solvent extraction along with cation-exchange and alpha-hydroxy-isobutyrate (AHIB) columns, are employed to achieve a clean separation of the isotopes. Production Campaigns 74–77 are discussed in depth for 252 Cf, 249 Bk, and 254 Es production and isolation of 249 Bk and 254 Es. An attempt to isolate 257 Fm in Campaign 77 is discussed as well. Table 1 summarizes the total amount of material isolated in each campaign.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2021

Structural and spectroscopic characterization of an einsteinium complex

The transplutonium elements (atomic numbers 95–103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies. Here we characterize a coordination complex of einsteinium, using less than 200 nanograms of 254 Es (with half-life of 275.7(5) days), with an organic hydroxypyridinone-based chelating ligand. X-ray absorption spectroscopic and structural studies are used to determine the energy of the L 3 -edge and a bond distance of einsteinium. Photophysical measurements show antenna sensitization of EsIII luminescence; they also reveal a hypsochromic shift on metal complexation, which had not previously been observed in lower-atomic-number actinide elements. Here, these findings are indicative of an intermediate spin–orbit coupling scheme in which j–j coupling (whereby single-electron orbital angular momentum and spin are first coupled to form a total angular momentum, j) prevails over Russell–Saunders coupling. Together with previous actinide complexation studies, our results highlight the need to continue studying the unusual behaviour of the actinide elements, especially those that are scarce and short-lived.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗