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Title: Investigation of the Unoccupied Electronic Structure of UO2 with Bermstrahlung Isochromat Spectroscopy and X-Ray Absorption Spectroscopy

Abstract

UO{sub 2} is an important nuclear fuel for electrical power generation. Global goal : Actinides (5f electron systems) exhibit fascinating physical and chemical properties, due to 5f electron correlation, including the highly radioactive systems such as Pu. Onsite Instrumentation: A spectroscopic system containing spin resolved photoelectron spectroscopy (SRPES) and bremsstrahlung isochromat spectroscopy (BIS) has been built and commissioned at LLNL. ALS Instrumentation: The XAS was done on Beamline 8. Both Total Electron Yield (TEY) and Total Fluorescence Yield (TFY) were used. TFY is less surface sensitive than TEY. A combined experimental and theoretical study of Uranium Dioxide has been performed, including XAS, BIS, XPS and spectral simulations. The Conduction Bands or Unoccupied Density of States (UDOS) of UO{sub 2} are shown to be divided into two parts, the lower region being U5f-O2p and the upper region U6d-O2p. This means that UO{sub 2} is an f-f Mott Insulator, electron-correlated system. The keys to success with the XAS were the (1) the utilization of both TEY and TFY and (2) the accurate co-location of the uranium and oxygen states, which in turn hinged upon a proper calibration of the gratings of the beamline monochromator. The calibration of the gratings was greatly aidedmore » by the availibility of the O1s XAS from 1st, 2nd and 3rd order light. The success of this approach to differentiation of the Uranium UDOS into U5f and U6d components is of great importance and bodes well for its application to other actinide systems. Our ultimate goal remains Pu and its electron correlation.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1022156
Report Number(s):
LLNL-PROC-475252
TRN: US1104163
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: 41emes Journees des Actinides, Stara Lesna, Slovakia, Apr 09 - Apr 12, 2011
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ACTINIDES; BREMSSTRAHLUNG; CALIBRATION; CHEMICAL PROPERTIES; ELECTRON CORRELATION; ELECTRONIC STRUCTURE; ELECTRONS; FLUORESCENCE; LAWRENCE LIVERMORE NATIONAL LABORATORY; NUCLEAR FUELS; OXYGEN; PHOTOELECTRON SPECTROSCOPY; POWER GENERATION; SPECTROSCOPY; SPIN; URANIUM; URANIUM DIOXIDE; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Tobin, J G, Yu, S W, Crowhurst, J C, Sharma, S, Dewhurst, J K, Olalde-Velasco, P, Yang, W L, and Siekhaus, W J. Investigation of the Unoccupied Electronic Structure of UO2 with Bermstrahlung Isochromat Spectroscopy and X-Ray Absorption Spectroscopy. United States: N. p., 2011. Web.
Tobin, J G, Yu, S W, Crowhurst, J C, Sharma, S, Dewhurst, J K, Olalde-Velasco, P, Yang, W L, & Siekhaus, W J. Investigation of the Unoccupied Electronic Structure of UO2 with Bermstrahlung Isochromat Spectroscopy and X-Ray Absorption Spectroscopy. United States.
Tobin, J G, Yu, S W, Crowhurst, J C, Sharma, S, Dewhurst, J K, Olalde-Velasco, P, Yang, W L, and Siekhaus, W J. Thu . "Investigation of the Unoccupied Electronic Structure of UO2 with Bermstrahlung Isochromat Spectroscopy and X-Ray Absorption Spectroscopy". United States. https://www.osti.gov/servlets/purl/1022156.
@article{osti_1022156,
title = {Investigation of the Unoccupied Electronic Structure of UO2 with Bermstrahlung Isochromat Spectroscopy and X-Ray Absorption Spectroscopy},
author = {Tobin, J G and Yu, S W and Crowhurst, J C and Sharma, S and Dewhurst, J K and Olalde-Velasco, P and Yang, W L and Siekhaus, W J},
abstractNote = {UO{sub 2} is an important nuclear fuel for electrical power generation. Global goal : Actinides (5f electron systems) exhibit fascinating physical and chemical properties, due to 5f electron correlation, including the highly radioactive systems such as Pu. Onsite Instrumentation: A spectroscopic system containing spin resolved photoelectron spectroscopy (SRPES) and bremsstrahlung isochromat spectroscopy (BIS) has been built and commissioned at LLNL. ALS Instrumentation: The XAS was done on Beamline 8. Both Total Electron Yield (TEY) and Total Fluorescence Yield (TFY) were used. TFY is less surface sensitive than TEY. A combined experimental and theoretical study of Uranium Dioxide has been performed, including XAS, BIS, XPS and spectral simulations. The Conduction Bands or Unoccupied Density of States (UDOS) of UO{sub 2} are shown to be divided into two parts, the lower region being U5f-O2p and the upper region U6d-O2p. This means that UO{sub 2} is an f-f Mott Insulator, electron-correlated system. The keys to success with the XAS were the (1) the utilization of both TEY and TFY and (2) the accurate co-location of the uranium and oxygen states, which in turn hinged upon a proper calibration of the gratings of the beamline monochromator. The calibration of the gratings was greatly aided by the availibility of the O1s XAS from 1st, 2nd and 3rd order light. The success of this approach to differentiation of the Uranium UDOS into U5f and U6d components is of great importance and bodes well for its application to other actinide systems. Our ultimate goal remains Pu and its electron correlation.},
doi = {},
url = {https://www.osti.gov/biblio/1022156}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {3}
}

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