Experimental Benchmarking of Pu Electronic Structure
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0893-JJ03-05.1
Experimental Benchmarking of Pu Electronic Structure J.G. Tobin1,*, K.T. Moore1, B.W. Chung1, M.A. Wall1, A.J. Schwartz1, B.B. Ebbinghaus1, M.T. Butterfield1, N.E. Teslich Jr. 1, R.A. Bliss1, S.A. Morton1,#, S.W. Yu1, T. Komesu2, G.D. Waddill2, G. van der Laan3, and A.L. Kutepov4 1. Lawrence Livermore National Laboratory, Livermore, CA, USA 94550 2. University of Missouri-Rolla, Rolla, MO 3. Synchrotron Radiation Source, Daresbury Laboratory, Warrington, WA4 4AD, UK 4. Russian Federation Nuclear Center, Inst. of Tech. Physics (VNIITF), Snezhinsk, Russia *Contact author: [email protected] #Present Address: Advanced Light Source, LBNL, Berkeley, CA
Abstract The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy [1], x-ray absorption spectroscopy [1,2,3,4], electron energy loss spectroscopy [2,3,4], Fano Effect measurements [5], and Bremstrahlung Isochromat Spectroscopy [6], including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples. [2,3,6] I
Motivation
The objective of this work is to develop and apply advanced diagnostics to the understanding of aging of Pu. Advanced characterization techniques such as photoelectron and x-ray absorption spectroscopy will provide fundamental data on the electronic structure of Pu phases. These data are crucial for the validation of the electronic structure methods. The fundamental goal of this project is to narrow the parameter space for the theoretical modeling of Pu aging. The short-term goal is to perform experiments to validate electronic structure calculations of Pu. The long-term goal is to determine the effects of aging upon the electronic structure of Pu. Many of the input parameters for aging models are not directly measurable. These parameters will need to be calculated or estimated. Thus a First Principles-Approach Theory is needed, but it is unclear what terms are important in the Hamiltonian. (HY = EY ) Therefore, experimental data concerning the 5f electronic structure are needed, to determine which terms in the Hamiltonian are important.
0893-JJ03-05.2
II. IIa.
Present Status Present Status: Spectroscopic Observation of Aging in Pu
Resonant Photoemission, a variant of Photoelectron Spectroscopy, has been dem
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