There is a great need to study the interaction of actinide species with solid surfaces. Knowledge of these fundamental interactions is critical to the understanding of a variety of processes in the areas of environmental and nuclear materials, including sorption reactions of Pu species from solution onto mineral grain surfaces in an environmental setting; interactions of Pu compounds in waste and process streams with contacting surfaces; and surface reactions of Pu at phase boundaries in actinide materials systems. Furthermore, studies of these reactions will allow us to extend the understanding of the chemistry in these strongly f-electron dominated systems. This is critical, as it is one of the unique challenges in chemistry and materials science at our national laboratories, as exemplified by the greater than $25M annual budget of the nuclear waste programs at Los Alamos National Laboratory.

      I have used soft x-ray techniques such photoelectron (PES), x-ray emission (SXE), and x-ray absorption spectroscopes (XAS) to determine electronic and geometric structures of many systems. These techniques are direct probes of the electronic structure of an interface and I plan to put these techniques to use studying the actinides. For example in the case of Pu it would be possible to determine: the oxidation state of the Pu, the number of Pu species present, and the direction of charge transfer between the substrate and the adsorbate. Local atomic structure (bond lengths, angles, bonding sites) can also be determined using these techniques due to interference properties of the emitted photon (fluorescence holography (SXE)) or photoelectron (photoelectron diffraction (PED), extended x-ray absorption fine structure (XAS)).

      Specifically, I would like to use these techniques to improve our understanding of the following areas:

• Photoemission and X-ray absorption spectroscopy studies of actinide molecular solids (fundamental properties, baseline chemistry).
• Photoemission studies of the chemistry of actinide adsorption at environmentally relevant surfaces (environmental fate and disposition).
• Fundamental surface chemistry and spectroscopy of actinide metal and actinide oxide surfaces interacting with small molecules from the gas phase (fundamental, well con-trolled interfacial chemistry).
• Local environmental degradation or passivation effects at surfaces and phase boundaries through small molecule chemistry.
• Fundamental understanding of the reason for differences in Pu surface reactivity in various allotropic forms and in the transition through the actinides, from delocalized to localized f-electron states.
• Intrinsic aging effects at surfaces or interfaces (grain, phase, and materials boundaries) through fission initiated reactions.
• Ability to solve engineering problems for Stockpile Stewardship programs by building a Pu surface chemistry knowledge base and expertise.