Physical Sciences and Mathematics Commons^™

K-Shell X-Ray Spectroscopy Of Atomic Nitrogen, M. M. Sant'anna, Gunnar Ohrwall, Wayne C. Stolte, Alfred S. Schlachter, Dennis W. Lindle, B. M. Mclaughlin

Chemistry and Biochemistry Faculty Research

Absolute K-shell photoionization cross sections for atomic nitrogen have been obtained from both experiment and state-of-the-art theoretical techniques. Because of the difficulty of creating a target of neutral atomic nitrogen, no high-resolution K-edge spectroscopy measurements have been reported for this important atom. Interplay between theory and experiment enabled identification and characterization of the strong 1s → np resonance features throughout the threshold region. An experimental value of 409.64 ± 0.02 eV was determined for the K-shell binding energy.

Jahn-Teller Coupling And Fragmentation After Core-Shell Excitation Ini Cf4 Investigated By Partial-Ion-Yield Spectroscopy, Renaud Guillemin, Wayne C. Stolte, Maria Novella Piancastelli, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

We investigate fragmentation processes induced by core-level photoexcitation in CF4 at both the carbon and fluorine K edges by means of partial-ion-yield spectroscopy. The molecule CF₄ is a textbook example of systems in which Jahn-Teller coupling strongly manifests itself in the photoabsorption spectrum. Spectral features related to Jahn-Teller and quasi-Jahn-Teller splitting are observed, and important differences in the fragmentation pathways are revealed depending on the symmetries of the core-excited states. We interpret these experimental observations on the grounds of symmetry lowering from the Td to the C3v point group as well as preferential orientation with respect …

Full Multiple Scattering Analysis Of Xanes At The Cd L 3- And O K- Edges In Cdo Films Combined With A Soft-X-Ray Emission Investigation, I. N. Demchenko, J. D. Denlinger, M. Chernyshova, K. M. Yu, D. T. Speaks, P. Olalde-Velasco, Oliver Hemmers, W. Walukiewicz, A. Derkachova, K. Lawniczak-Jablonska

Environmental Studies Faculty Publications

X-ray absorption near edge structure (XANES) at the cadmium L3 and oxygen K edges for CdO thin films grown by pulsed laser deposition method, is interpreted within the real-space multiple scattering formalism, FEFF code. The features in the experimental spectra are well reproduced by calculations for a cluster of about six and ten coordination shells around the absorber for L3 edge of Cd and K edge of O, respectively. The calculated projected electronic density of states is found to be in good agreement with unoccupied electronic states in experimental data and allows to conclude that the orbital character of the …

Sulfur K-Edge Photo-Fragmentation Of Ethylene Sulfide, Wayne C. Stolte, Gunnar Ohrwall

Chemistry and Biochemistry Faculty Research

We have investigated the photofragmentation properties of the three-membered ring heterocyclic molecule ethylene sulfide or thiirane, C₂H₄S, by time-of-flight mass spectroscopy. Positive ions have been collected as a function of photon energy around the S K ionization threshold. Branching ratios were derived for all detected ions, which are informative of the decay dynamics and photofragmentation patterns of the core-excited species. We present a new assignment of the spectral features around the S K-edge.

Fragmentation Properties Of Three-Membered Ring Heterocyclic Molecules By Partial Ion Yield Spectroscopy: C2h4o And C2h4s, Wayne C. Stolte, I. Dumitriu, S-W Yu, Gunnar Ohrwall, Maria Novella Piancastelli, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

We investigated the photofragmentation properties of two three-membered ring heterocyclic molecules, C₂H₄O and C₂H₄S, by total and partial ion yield spectroscopy. Positive and negative ions have been collected as a function of photon energy around the C 1s and O 1s ionization thresholds in C₂H₄O, and around the S 2p and C 1s thresholds in C₂H₄S. We underline similarities and differences between these two analogous systems. We present a new assignment of the spectral features around the C K-edge and the sulfur L_{2 …}

Experimental And Theoretical Investigation Of Molecular Field Effects By Polarization-Resolved Resonant Inelastic X-Ray Scattering, Stephane Carniato, Renaud Guillemin, Wayne C. Stolte, Loic Journel, Richard Taieb, Dennis W. Lindle, Marc Simon

Chemistry and Biochemistry Faculty Research

We present a combined theoretical and experimental study of molecular field effects on molecular core levels. Polarization-dependent resonant inelastic x-ray scattering is observed experimentally after resonant K-shell excitation of CF₃Cl and HCl. We explain the linear dichroism observed in spin-orbit level intensities as due to molecular field effects, including singlet-triplet exchange, and interpret this behavior in terms of population differences in the 2p_x,y,z inner-shell orbitals. We investigate theoretically the different factors that can affect the electronic populations and the dynamical R dependence of the spin-orbit ratio. Finally, the results obtained are used to interpret the L-shell …

Partial Ion Yield Sspectroscopy Around The Cl 2p And C 1s Ionization Thresholds In Cf3cl, D. Ceolin, Maria Novella Piancastelli, Wayne C. Stolte, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

We present a partial ion yield experiment on freon 13, CF₃Cl, excited in the vicinity of the C 1s and Cl 2p ionization thresholds. We have collected a large amount of cationic fragments and a few anionic fragments at both edges. We have observed a strong intensity dependence of Rydberg transitions with ion fragment size for the CF_nCl⁺ and CF_n⁺/F⁺ (n=0–3) series at both the Cl 2p and C 1s ionization edges. Selectivity in the fragmentation processes involving the C–Cl and C–F bonds are highlighted by the intensities of the C …

Yttrium And Hydrogen Superstructure And Correlation Of Lattice Expansion And Proton Conductivity In The Bazr0.9y0.1o2.95 Proton Conductor, A. Braun, A. Ovalle, V. Pomjakushin, A. Cervellino, S. Erat, Wayne C. Stolte, T. Graule

Chemistry and Biochemistry Faculty Research

Bragg reflections in Y-resonant x-ray diffractograms of BaZr_0.9Y_0.1O_2.95 (BZY10) reveal that Y is organized in a superstructure. Comparison with neutron diffraction superstructure reflections in protonated/deuterated BZY10 suggests that both superstructures are linked, and that protons move in the landscape imposed by the Y. The thermal lattice expansion decreases abruptly for protonated BZY10 at T≥648±20 K, coinciding with the onset of lateral proton diffusion and suggesting a correlation of structural changes and proton conductivity. The chemical shift in the Y L₁-shell x-ray absorption spectra reveals a reduction from Y³⁺ toward Y²⁺ upon …

Linear Dichroism In Resonant Inelastic X-Ray Scattering To Molecular Spin-Orbit States, Renaud Guillemin, Stephane Carniato, Wayne C. Stolte, Loic Journel, Richard Taieb, Dennis W. Lindle, Marc Simon

Chemistry and Biochemistry Faculty Research

Polarization-dependent resonant inelastic x-ray scattering (RIXS) is shown to be a new probe of molecular-field effects on the electronic structure of isolated molecules. A combined experimental and theoretical analysis explains the linear dichroism observed in Cl 2p RIXS following Cl 1s excitation in HCl and CF₃Cl as due to molecular-field effects, including singlet-triplet exchange, indicating polarized-RIXS provides a direct probe of spin-orbit-state populations applicable to any molecule.

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Matrix, Spencer M. Steinberg, Gary Cerefice, David W. Emerson

Separations Campaign (TRP)

Observations related to the oxidation of iodide to iodine (I₂) or hypoiodic acid (HIO) by MnO₂ were continued. The formation of triiodide presumable involves the adsorption of iodide onto the MnO₂ surface (perhaps displacing a surface hydroxyl group). The iodide should be subsequently oxidized and released back into solution as IOH or I₂, which rapidly forms I₃ ^-. The kinetic data has been modeled as a first order process. First order rate constants have been obtained for the formation of iodine in the presence of MnO₂. The increase in iodide …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective was to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in RTIL solutions, and use this data to effectively separate species with very similar chemical properties.

In consultation with a DOE collaborator, electrochemical methods and materials were evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing the ability to selectively target and sequester individual species from mixtures. This project, in its third year, successfully completed phases 1, 2. Phase 3 was partially completed. The project expanded to include phase 4.

The following were specific goals for 2007-2008:

• To …

Fundamental Chemistry Of U And Pu In The Tbp-Dodecane-Nitric Acid System, Kenneth Czerwinski

Separations Campaign (TRP)

The research objective is to experimentally evaluate the fundamental speciation of Pu and U in the TBP-dodecane-nitric acid- AHA system and the effect of pertechnetate, specifically:

• To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration, actinide ion concentration, temperature, and time.

• To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and …

Evaluation Of Fundamental Radionuclide Extraction Data For Urex, Kenneth Czerwinski

Separations Campaign (TRP)

The speciation of technetium and actinides in advanced solvent extraction systems is the basis for their manipulation in separations. The ability to understand and predict radionuclide speciation is paramount to successful modeling of proposed separation systems. This project will examine the speciation of radionuclides in different stages of the uranium extraction (UREX) separation scheme, providing data useful to modeling. The areas to be examined include the speciation of uranium and plutonium with tributylphosphate and the kinetics and thermodynamics of lanthanides and actinides in the TALSPEAK (Trivalent actinide lanthanide separation by phosphorous reagent extraction from aqueous complexes) system. The complexation constants …

Criticality Studies For Urex Processes, Denis Beller

Separations Campaign (TRP)

The completion of criticality experiments for mixtures of transuranic actinides (TRU; includes neptunium, plutonium, americium, and curium) that will be created during the separation of used nuclear fuel may be a requirement in order to construct prototype plants for the Global Nuclear Energy Partnership (GNEP). In this program and the Advanced Fuel Cycle Research and Development (AFC R&D) program that supports it, economic and environmental methods are being developed to reduce the impact of waste from commercial nuclear fuel cycles.

Recycling of used fuel by chemically separating it into U, fission products, and TRU would be the first step in …

F-Element Electrochemistry In Rtil Solutions: Electrochemical Separation Of Lanthanides And Actinides, David W. Hatchett

Separations Campaign (TRP)

Electrochemical methods can be used to effectively separate actinide and lanthanide species from complex mixtures. This is based on the unique electrochemical properties of each specific target species. In studies it has been found that, with the exception of Ce, aqueous solutions provide unsuitable electrochemical windows to effectively evaluate the thermodynamic properties that are useful for chemical separations. Therefore, a more novel approach was examined which eliminated the aqueous solution with a room temperature ionic liquid (RTIL) solution. RTIL solutions do not suffer from the side reactions that are prominent in aqueous environments. In addition, the potential window is much …

Photofragmentation Of Sif4 Upon Si 2p And F 1s Core Excitation: Cation And Anion Yield Spectroscopy, Maria Novella Piancastelli, Wayne C. Stolte, Renaud Guillemin, A. Wolska, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

We have studied the fragmentation dynamics of core-excited SiF₄ by means of soft-x-ray photoexcitation and partial positive and negative ion yield measurements around the Si L_2,3-shell and F K-shell ionization thresholds. All detectable ionic fragments are reported and we observe significant differences between the various partial ion yields near the Si 2p threshold. The differences are similar to our previous results from CH₃Cl showing more extended fragmentation in correspondence to transitions to Rydberg states. At variance with smaller systems, we observe negative ion production in the shape resonance region. This can be related …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Matrix, Spencer M. Steinberg, Gary Cerefice, David W. Emerson

Separations Campaign (TRP)

The stability of the association of iodine with FCC and NOM products were studied. Product distributions for the various matrices under various reaction conditions were examined in order to maximize the binding of iodine. The recovery of the iodine from the sequestration matrices was also examined, along with the conversion of the iodine to matrices more suitable for geological storage and/or use as transmutation targets.

The following are the specific research objectives and goals:

• Develop bench-scale experimental set-up and procedures for simulating plutonium extraction process (PUREX) head-end vapor phase.
• Develop experimental procedures for evaluating iodine sequestering methods using bench-scale procedures. …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objectives of this project are to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in RTIL solution, and to use this data to effectively separate species with very similar chemical properties. In consultation with a national laboratory collaborator, electrochemical methods and materials will be evaluated and used to exploit the thermodynamic differences between similar chemical species, enhancing the ability to selectively target and sequester individual species from mixtures. This project is in its third year and has successfully completed phases 1 and 2. Phase 3 has been partially completed. The tasks have been expanded …

Fundamental Chemistry Of U And Pu In The Tbp-Dodecane-Nitric Acid System, Kenneth Czerwinski

Separations Campaign (TRP)

The research objective is to experimentally evaluate the fundamental speciation of Pu and U in the TBP-dodecane-nitric acid- AHA system and the effect of pertechnetate, specifically:

To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration, actinide ion concentration, temperature, and time.

To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and Pu are …

F-Element Electrochemistry In Room Temperature Ionic Liquids, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This proposal focuses on f-element electrochemistry in room temperature ionic liquids (RTILs). The ultimate goal is to fully characterize the oxidation/reduction of elements in RTILs to establish the baseline thermodynamic and kinetic data for these systems. The data will be used to critically evaluate the ability to use electrochemical methods for controlled, potential mediated, separation off-elements by electroplating on electrodes surfaces. Factors that will influence the ability to measure the redox processes in f-elements in RTIL solutions and electroplating on electrode surfaces include the structure, solubility, and stability of the target species in these solutions. These factors will be addressed …

Criticality Studies For Urex Processes, Denis Beller

Separations Campaign (TRP)

The completion of criticality experiments for mixtures of transuranic actinides (TRU–includes Np, Pu, Am, and Cm) that will be created during the separation of used nuclear fuel may be a requirement in order to construct prototype plants for the Global Nuclear Energy Partnership. In this program and the Advanced Fuel Cycle Research and Development (AFC R&D) program that supports it, economic and environmental methods are being developed to reduce the impact of waste from commercial nuclear fuel cycles.

Recycling of used fuel by chemically separating it into U, fission products, and TRU would be the first step in this new …

Evaluation Of Fundamental Radionuclide Extraction Data For Urex, Kenneth Czerwinski

Separations Campaign (TRP)

The speciation of technetium and actinides in advanced solvent extraction systems is the basis for their manipulation in separations. The ability to understand and predict radionuclide speciation is paramount to successful modeling of proposed separation systems. This project will examine the speciation of radionuclides in different stages of the UREX separation scheme, providing data useful to modeling. The areas to be examined include the speciation of U and Pu with tributylphosphate and the kinetics and thermodynamics of lanthanides and actinides in the TALSPEAK system. The complexation constants of U and Pu with tributylphosphate will be evaluated. In the TALSPEAK system, …

Criticality Studies Of Dilute Plutonium Mixtures For Urex Processes, Denis Beller

Separations Campaign (TRP)

The completion of criticality experiments for mixtures of higher actinides (HA, includes neptunium, plutonium, americium, and curium) that will be created during the separation of used nuclear fuel has been identified as a requirement to construct prototype plants such as the Engineering-Scale Demonstration (ESD) and the Advanced Fuel Cycle Facility (AFCF) for the Global Nuclear Energy Partnership (GNEP). GNEP is a program to develop a worldwide consensus to enable the expanded use of economical, environmental nuclear energy to meet growing electricity demand. In this program and the Advanced Fuel Cycle R&D program (AFC) that supports it, we are developing economic …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Organic Matrix: Quaterly Report January-March 2006, Spencer M. Steinberg

Separations Campaign (TRP)

Project Highlights:

• Established that iodide can be oxidized by MnO₂ to I₂ at pHs of 4-8 and moderate temperature.

• Demonstrated that p-hydroxybenzoic acid can be iodinated by MnO₂ and KI at pHs of 2-8.

• Established that humic acids can be iodinated by MnO₂ and iodide at room temperature in pH range of 4-8.

The Electrochemical Separation Of Curium And Americium: Quaterly Report January - March, 2006, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium. For two and a half years, research has been actively performed on this project, and is currently on schedule for the proposed timelines.

Progress:

• The electrochemical characterization of Ce and Eu complexed with EDTA, NTA, and Citrate has been completed.

• Synthesis of the polymer substrate and the chelating ligand is underway. Approximately 50 grams of disulfide has been produced to produce the chelating thiol group required for the last set of studies.

• Gold substrates have been prepared to perform …

Femtosecond Nuclear Motion Of Hcl Probed By Resonant X-Ray Raman Scattering In The Cl 1s Region, Marc Simon, Loic Journel, Stephane Carniato, Richard Taieb, I. Minkov, Faris Gel'mukhanov, P. Salek, H. Agren, Renaud Guillemin, Wayne C. Stolte, A. C. Hudson, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Femtosecond dynamics are observed by resonant x-ray Raman scattering (RXS) after excitation along the dissociative Cl 1s→6ơ* resonance of gas-phase HCl. The short core-hole lifetime results in a complete breakdown of the common nondispersive behavior of soft-x-ray transitions between parallel potentials. We evidence a general phenomenon of RXS in the hard-x-ray region: a complete quenching of vibrational broadening. This opens up a unique opportunity for superhigh resolution x-ray spectroscopy beyond vibrational and lifetime limitations.

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Matrix, Spencer M. Steinberg, Gary Cerefice, David W. Emerson

Separations Campaign (TRP)

The recovery of iodine released during the processing of used nuclear fuel poses a significant challenge to the transmutation of nuclear waste. Iodine-129, a long-lived fission product formed by both commercial nuclear power generation and nuclear weapons production, is released when reprocessing nuclear fuel. Since iodine can be concentrated in the human thyroid, any uncontrolled release of iodine may result in an increased rate of thyroid cancer in the exposed population. For this reason, recovery of iodine is important for implementing any nuclear transmutation strategy.

The stability of the association of iodine with FCC and NOM products are studied. Product …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in aqueous solution and use this data to effectively separate species with very similar chemical properties. In consultation with a national laboratory collaborators, electrochemical methods and materials will be evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing the ability to selectively target and sequester individual species from mixtures. This project is in its third year and has successfully completed Phases 1 and 2.

The following were specific goals for this year:

• To develop a fundamental …

Fundamental Chemistry Of U And Pu In The Tbp-Dodecane-Nitric Acid System, Kenneth Czerwinski, Byron Bennett

Separations Campaign (TRP)

The research objectives of this project are as follows:

• To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration (by the addition of NaNO₃), actinide ion concentration, temperature, and time.
• To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and Pu are evaluated as a function of AHA concentration, metal ion concentration, …

The Electrochemical Separation Of Curium And Americium: Quaterly Report April - June, 2005, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Results

• We have completed the electrochemical investigation in of the Ce³⁺/Ce⁴⁺ redox couple and have determined the optimum experimental conditions.

• Computer modeling of the cerium using the JChess speciation-modeling program has been completed for the Ce redox couple. Traditional complexing ligands such as EDTA, oxalate, NTA, phosphate, acetate, and sulfate have been purchased and will be used to initiate the complexation and electrochemical characterization.

• Electrochemical investigations have continued on the Eu²⁺/Eu³⁺ redox …