Nuclear Chemistry Nuclear Environmental Chemistry - Heavy elements are synthesized, and first-time chemistry of the heaviest elements is explored. Molecular-level structural information is essential to understand actinide interaction in environmental solutions, with minerals, soil microbes and at interfaces of these components.
Our research interests focus on two main areas: (1) the production, nuclear properties, and chemistry and of the heaviest elements and (2) fundamental research on the environmental behavior of non-radioactive and radioactive metal ions, with emphasis on actinides.
I. Production, Chemistry and Nuclear properties of the heaviest elements.
The heaviest elements are synthesized at the Lawrence Berkeley National Laboratory's (LBNL) 88-inch Cyclotron using the compound nucleus Berkeley Gas-filled Separator (BGS). We study the chemical properties of the heaviest elements to explore if relativistic effects cause a noticeable change in chemical behavior compared to their lighter homologues, thus establishing the architecture of the periodic system for the heaviest elements. Until now, the most important aspect of a chemical separation system used for study of the heaviest elements was the need for an extremely efficient separation of the heavy element atoms from interfering radioactivities concurrently produced in the nuclear reactions used. This severely limited the chemical systems that could be studied; for example, bohrium (107) and hassium (108) could only be studied by a few very simple and rugged gas phase experiments to form oxychlorides and oxides, and no aqueous phase experiments were ever performed. We have pioneered the use of the BGS as a pre-separator to provide high-purity heavy element samples for chemical separations. With the use of the BGS, there is no longer a need for the chemical system to separate heavy elements from interfering activities. This allows development of a very broad range of chemical separation systems that are better able to elucidate the chemical properties of the heaviest elements, and make the necessary comparison to the chemical behavior of chemical homologues. We are currently expanding the capabilities of the BGS for use of radioactive targets. This will give us access to several significantly longer-lived isotopes of elements 104-108 with half lives long enough for chemical separations.
In collaboration with Swiss and German colleagues, we have studied for the first time the chemistry of bohrium (107) and hassium (108). We are continuing to study the chemistry of elements rutherfordium through hassium (104-108) in aqueous and gas phase with more complex second generation chemical reaction systems, and are developing methods to explore the chemistry of elements 112 and 114. These one-atom-at-a time chemistry studies are unique within the U.S.
II. Nuclear Chemistry related to fundamental processes in the environment.
Solution Speciation and Interfacial Reactions of actinides on Metal Oxides and Oxyhydroxides. The research spans analytical chemistry, solution thermodynamics and kinetics, and solution/solid interfacial reactions. We are advancing the molecular understanding of actinide sorption by studying the behavior of the actinides uranium, neptunium, plutonium, americium, and curium on environmentally relevant solid substrates using modern spectroscopic techniques to explore the existence of complexes postulated by surface complexation modeling. Knowledge of the actinide speciation in solution is a prerequisite for the sorption studies. Besides conventional speciation techniques (potentiometric titration, spectrophotometry, solvent extraction, electrochemistry, etc.), we use more sensitive laser-induced fluorescence spectroscopy and synchrotron-based X-ray absorption spectroscopy (XAS) to provide molecular-level structural information of solids, solutions, and solution/solids interfaces.
Professor, born 1949; Dipl. Chem. (M.Sc.), Freie Universität Berlin, Germany (1976); Dr. rer. nat (Ph.D.), Freie Universität Berlin, Germany (1980); 1998 - present Faculty Senior Scientist, Lawrence Berkeley National Laboratory; 1998 - 2002 Founding Director, Glenn T. Seaborg Center, Lawrence Berkeley National Laboratory; 1993 - 1998 Professor of Radiochemistry, Technische Universität, Dresden, Germany; 1993 - 1998 Director, Institute of Radiochemistry, Forschungszentrum Rossendorf e.V., Germany; 1980 - 1993 Investigator, Lawrence Berkeley Laboratory/University of California; 2007 Chair, Division of Nuclear Chemistry and Technology, American Chemical Society; 1997 - 1998 Chair, Gesellschaft Deutscher Chemiker (GDCh, Germany Chemical Society), Fachgruppe Nuklearchemie (Nuclear Chemistry Section); Member: American Chemical Society (ACS); Gesellschaft Deutscher Chemiker (GDCh); Kerntechnische Gesellschaft e.V. (KTG, German Nuclear Society).