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Articles 1 - 30 of 55
Full-Text Articles in Physics
Dicationic Stilbazolium Salts: Structural, Thermal, Optical, And Ionic Conduction Properties, Pradip K. Bhowmik, Jung J. Koh, David King, Haesook Han, Benoît Heinrich, Bertrand Donnio, Daniel Zaton, Alfonso Martinez-Felipe
Dicationic Stilbazolium Salts: Structural, Thermal, Optical, And Ionic Conduction Properties, Pradip K. Bhowmik, Jung J. Koh, David King, Haesook Han, Benoît Heinrich, Bertrand Donnio, Daniel Zaton, Alfonso Martinez-Felipe
Chemistry and Biochemistry Faculty Research
Two series of new dicationic stilbazolium salts containing tosylate and triflimide counterions, respectively, were synthesized and characterized by spectroscopic techniques and elemental analysis. Despite of their promesogenic structures, none of these salts are mesomorphous, and instead they solely exhibit crystalline polymorphism, as deduced from differential scanning calorimetry, polarizing optical microscopy and variable temperature X-ray measurements. These salts were also found to be highly thermally stable with decomposition temperatures occurring well above 300 °C, and up to 367 °C for the triflimide salts, as determined by thermogravimetric analysis. UV–Vis absorption and photoluminescent properties were examined in both solution and in the …
Recovery Of High Specific Activity Molybdenum-99 From Accelerator-Induced Fission On Low-Enriched Uranium For Technetium-99m Generators, M. Alex Brown, Nathan Johnson, Artem V. Gelis, Milan Stika, Anna G. Servis, Alex Bakken, Christine Krizmanich, Kristin Shannon, Peter Kozak, Amanda Barnhart, Chad Denbrock, Nicolas Luciani, Terry Grimm, Peter Tkac
Recovery Of High Specific Activity Molybdenum-99 From Accelerator-Induced Fission On Low-Enriched Uranium For Technetium-99m Generators, M. Alex Brown, Nathan Johnson, Artem V. Gelis, Milan Stika, Anna G. Servis, Alex Bakken, Christine Krizmanich, Kristin Shannon, Peter Kozak, Amanda Barnhart, Chad Denbrock, Nicolas Luciani, Terry Grimm, Peter Tkac
Chemistry and Biochemistry Faculty Research
A new process was developed to recover high specific activity (no carrier added) 99Mo from electron-accelerator irradiated U3O8 or uranyl sulfate targets. The process leverages a novel solvent extraction scheme to recover Mo using di(2-ethylhexyl) phosphoric acid following uranium and transuranics removal with tri-n-butyl phosphate. An anion-exchange concentration column step provides a final purification, generating pure 99Mo intended for making 99Mo/99mTc generators. The process was demonstrated with irradiated uranium targets resulting in more than 95% 99Mo recovery and without presence of fission products or actinides in the product.
Β -Technetium: An Allotrope With A Nonstandard Volume-Pressure Relationship, Emily Siska, Dean Smith, Christian Childs, Daniel Koury, Paul M. Forster, Keith V. Lawler, Ashkan Salamat
Β -Technetium: An Allotrope With A Nonstandard Volume-Pressure Relationship, Emily Siska, Dean Smith, Christian Childs, Daniel Koury, Paul M. Forster, Keith V. Lawler, Ashkan Salamat
Chemistry and Biochemistry Faculty Research
We report the synthesis and structure of the second allotrope of technetium, β-Tc. Transformative pathways are accessed at extreme conditions using the laser-heated diamond anvil cell and confirmed with in situ synchrotron x-ray diffraction and Raman spectroscopy. β-Tc is fully recoverable to ambient conditions, although counter to our DFT calculations predicting a face-centered-cubic lattice, we observe a tetragonal structure (I4/mmm) that exhibits further tetragonal distortion with pressure. β-Tc has an expanded volume relative to the hcp ground state phase, that when doped with nitrogen has an unexpected volume lowering. Such anomalous behavior is possibly indicative of a rare electronic phase …
Colossal Density-Driven Resistance Response In The Negative Charge Transfer Insulator Mns2, Dylan Durkee, Nathan Dasenbrock-Gammon, G. Alexander Smith, Elliot Snider, Dean Smith, Christian Childs, Simon A.J. Kimber, Keith V. Lawler, Ranga P. Dias, Ashkan Salamat
Colossal Density-Driven Resistance Response In The Negative Charge Transfer Insulator Mns2, Dylan Durkee, Nathan Dasenbrock-Gammon, G. Alexander Smith, Elliot Snider, Dean Smith, Christian Childs, Simon A.J. Kimber, Keith V. Lawler, Ranga P. Dias, Ashkan Salamat
Chemistry and Biochemistry Faculty Research
A reversible density driven insulator to metal to insulator transition in high-spin MnS2 is experimentally observed, leading with a colossal electrical resistance drop of 108 ω by 12 GPa. Density functional theory simulations reveal the metallization to be unexpectedly driven by previously unoccupied S22- σ3p∗ antibonding states crossing the Fermi level. This is a unique variant of the charge transfer insulator to metal transition for negative charge transfer insulators having anions with an unsaturated valence. By 36 GPa the emergence of the low-spin insulating arsenopyrite (P21/c) is confirmed, and the bulk metallicity is broken with the system returning to an …
Pressure- And Temperature-Dependent Inelastic Neutron Scattering Study Of The Phase Transition And Phonon Lattice Dynamics In Para-Terphenyl, Qingan Cai, Michael Mcintire, Luke L. Daemen, Chen Li, Eric Chronister
Pressure- And Temperature-Dependent Inelastic Neutron Scattering Study Of The Phase Transition And Phonon Lattice Dynamics In Para-Terphenyl, Qingan Cai, Michael Mcintire, Luke L. Daemen, Chen Li, Eric Chronister
Chemistry and Biochemistry Faculty Research
Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0-1.51 kbar and 10-30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, …
Machine Learning Corrected Quantum Dynamics Calculations, A. Jasinski, J. Montaner, R. C. Forrey, B. H. Yang, P. C. Stancil, Naduvalath Balakrishnan, J. Dai, A. Vargas-Hernandez, R. V. Krems
Machine Learning Corrected Quantum Dynamics Calculations, A. Jasinski, J. Montaner, R. C. Forrey, B. H. Yang, P. C. Stancil, Naduvalath Balakrishnan, J. Dai, A. Vargas-Hernandez, R. V. Krems
Chemistry and Biochemistry Faculty Research
Quantum scattering calculations for all but low-dimensional systems at low energies must rely on approximations. All approximations introduce errors. The impact of these errors is often difficult to assess because they depend on the Hamiltonian parameters and the particular observable under study. Here, we illustrate a general, system- and approximation-independent, approach to improve the accuracy of quantum dynamics approximations. The method is based on a Bayesian machine learning (BML) algorithm that is trained by a small number of exact results and a large number of approximate calculations, resulting in ML models that can generalize exact quantum results to different dynamical …
Non-Adiabatic Quantum Dynamics Of The Ultracold Li+Lina→ Li2+Na Chemical Reaction, B. K. Kendrick, M. Li, H. Li, S. Kotochigova, J. F.E. Croft, Balakrishnan Naduvalath
Non-Adiabatic Quantum Dynamics Of The Ultracold Li+Lina→ Li2+Na Chemical Reaction, B. K. Kendrick, M. Li, H. Li, S. Kotochigova, J. F.E. Croft, Balakrishnan Naduvalath
Chemistry and Biochemistry Faculty Research
We report non-adiabatic dynamics of the Li+LiNa→Li2+Na chemical reaction at cold and ultracold temperatures employing accurate ab initio electronic potential energy surfaces in a quantum dynamics formulation employing a diabatic representation. Results are compared against those from a single adiabatic ground state potential energy surface and a universal model based on the long-range interaction potential. We discuss signatures of non-universal behavior in the total rate coefficients as well as strong non-adiabatic effects in the state-to-state rotationally resolved rate coefficients.
Author Correction: Closing The Nuclear Fuel Cycle With A Simplified Minor Actinide Lanthanide Separation Process (Alsep) And Additive Manufacturing, Artem V. Gelis, Peter Kozak, Andrew T. Breshears, M. Alex Brown, Cari Launiere, Emily L. Campbell, Gabriel B. Hall, Tatiana G. Levitskaia, Vanessa E. Holfeltz, Gregg J. Lumetta
Author Correction: Closing The Nuclear Fuel Cycle With A Simplified Minor Actinide Lanthanide Separation Process (Alsep) And Additive Manufacturing, Artem V. Gelis, Peter Kozak, Andrew T. Breshears, M. Alex Brown, Cari Launiere, Emily L. Campbell, Gabriel B. Hall, Tatiana G. Levitskaia, Vanessa E. Holfeltz, Gregg J. Lumetta
Chemistry and Biochemistry Faculty Research
No abstract provided.
Closing The Nuclear Fuel Cycle With A Simplified Minor Actinide Lanthanide Separation Process (Alsep) And Additive Manufacturing, Artem V. Gelis, Peter Kozak, Andrew T. Breshears, M. Alex Brown, Cari Launiere, Emily L. Campbell, Gabreil B. Hall, Tatiana G. Levitskaia, Vanessa E. Holfeltz, Gregg J. Lumetta
Closing The Nuclear Fuel Cycle With A Simplified Minor Actinide Lanthanide Separation Process (Alsep) And Additive Manufacturing, Artem V. Gelis, Peter Kozak, Andrew T. Breshears, M. Alex Brown, Cari Launiere, Emily L. Campbell, Gabreil B. Hall, Tatiana G. Levitskaia, Vanessa E. Holfeltz, Gregg J. Lumetta
Chemistry and Biochemistry Faculty Research
Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle …
Stereodynamical Control Of A Quantum Scattering Resonance In Cold Molecular Collisions, Pablo G. Jambrina, James F.E. Croft, Hua Guo, Mark Brouard, Balakrishnan Naduvalath, F. Javier Aoiz
Stereodynamical Control Of A Quantum Scattering Resonance In Cold Molecular Collisions, Pablo G. Jambrina, James F.E. Croft, Hua Guo, Mark Brouard, Balakrishnan Naduvalath, F. Javier Aoiz
Chemistry and Biochemistry Faculty Research
Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HD (v=1, j=2) by collisions with ground state para-H2, the process is dominated by a single L=2 partial wave resonance centered around 0.1 K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome.
Rotational Quenching Of Hd Induced By Collisions With H2 Molecules, Yier Wan, Nadulvalath Balakrishnan, B. H. Yang, R. C. Forrey, P. C. Stancil
Rotational Quenching Of Hd Induced By Collisions With H2 Molecules, Yier Wan, Nadulvalath Balakrishnan, B. H. Yang, R. C. Forrey, P. C. Stancil
Chemistry and Biochemistry Faculty Research
Rate coefficients for rotational transitions in HD induced by H2 impact for rotational levels of HD j ≤ 8 and temperatures 10 K ≤ T ≤ 5000 K are reported. The quantum mechanical close-coupling (CC) method and the coupled-states (CS) decoupling approximation are used to obtain the cross-sections employing the most recent highly accurate H2–H2 potential energy surface (PES). Our results are in good agreement with previous calculations for low-lying rotational transitions The cooling efficiency of HD compared with H2 and astrophysical applications are briefly discussed.
The Purported Square Ice In Bilayer Graphene In A Nanoscale, Monolayer Object, Tod A. Pascal, Craig P. Schwartz, Keith V. Lawler, David Prendergast
The Purported Square Ice In Bilayer Graphene In A Nanoscale, Monolayer Object, Tod A. Pascal, Craig P. Schwartz, Keith V. Lawler, David Prendergast
Chemistry and Biochemistry Faculty Research
The phase diagram of water is complex, and interfacial effects can stabilize unusual structures at the nanoscale. Here, we employ bond order accelerated molecular dynamics simulations to show that upon encapsulation within bilayer graphene, water can spontaneously adopt a two-dimensional (monomolecular) layer of “square ice” at ambient conditions, instead of an encapsulated water droplet. Free energy calculations show that this motif is thermodynamically stable up to diameters of approximately 15 nm due to enhanced hydrogen bonding and favorable binding to the graphene sheets. Entropic losses due to solidification and reduced graphene–graphene binding enthalpy are opposing thermodynamic forces that conspire to …
Unraveling The Stereodynamics Of Cold Controlled Hd−H2 Collisions, James F. E. Croft, Naduvalath Balakrishnan, Meng Huang, Hua Guo
Unraveling The Stereodynamics Of Cold Controlled Hd−H2 Collisions, James F. E. Croft, Naduvalath Balakrishnan, Meng Huang, Hua Guo
Chemistry and Biochemistry Faculty Research
Measuring inelastic rates with partial-wave resolution requires temperatures close to a Kelvin or below, even for the lightest molecule. In a recent experiment, Perreault, Mukherjee, and Zare [Nat. Chem. 10, 561 (2018).] studied collisional relaxation of excited HD molecules in the v=1, j=2 state by para- and ortho-H2 at a temperature of about 1 K, extracting the angular distribution of scattered HD in the v=1, j=0 state. By state preparation of the HD molecules, control of the angular distribution of scattered HD was demonstrated. Here, we report a first-principles simulation of that experiment which enables us to attribute the main …
Angular And Dynamical Properties In Resonant Inelastic X-Ray Scattering: Case Study Of Chlorine-Containing Molecules, Renaud Guillemin, Wayne C. Stolte, Loic Journel, Stephane Carniato, Maria Novella Piancastelli, Dennis W. Lindle, Marc Simon
Angular And Dynamical Properties In Resonant Inelastic X-Ray Scattering: Case Study Of Chlorine-Containing Molecules, Renaud Guillemin, Wayne C. Stolte, Loic Journel, Stephane Carniato, Maria Novella Piancastelli, Dennis W. Lindle, Marc Simon
Chemistry and Biochemistry Faculty Research
Polarization-dependent resonant inelastic x-ray scattering (RIXS) has been shown to be a probe of molecular-field effects on the electronic structure of isolated molecules. In this experimental analysis we explain the linear dichroism observed in Cl 2p polarized RIXS following Cl 1s excitation of a series of chlorofluoromethanes (CF3Cl, CF2Cl2, CFCl3, and CCl4) as due to molecular-field effects, including singlet-triplet exchange. We present an approach to extract directly the 2p inner-shell electronic state populations from the experimental measurements. Using the angular properties of the measured KV emission we also are able to determine the value of the polarization anisotropy parameter βp …
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
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.
Resonant Inelastic X-Ray Scattering Of Methyl Chloride At The Chlorine K Edge, L. El Khoury, Loic Journel, Renaud Guillemin, Stephane Carniato, Wayne C. Stolte, T. Marin, Dennis W. Lindle, Marc Simon
Resonant Inelastic X-Ray Scattering Of Methyl Chloride At The Chlorine K Edge, L. El Khoury, Loic Journel, Renaud Guillemin, Stephane Carniato, Wayne C. Stolte, T. Marin, Dennis W. Lindle, Marc Simon
Chemistry and Biochemistry Faculty Research
We present a combined experimental and theoretical study of isolated CH3Cl molecules using resonant inelastic x-ray scattering (RIXS). The high-resolution spectra allow extraction of information about nuclear dynamics in the core-excited molecule. Polarization-resolved RIXS spectra exhibit linear dichroism in the spin-orbit intensities, a result interpreted as due to chemical environment and singlet-triplet exchange in the molecular core levels. From analysis of the polarization-resolved data, Cl 2px, y and 2pz electronic populations can be determined.
A New Method To Derive Electronegativity From Resonant Inelastic X-Ray Scattering, Stephane Carniato, Loic Journel, Renaud Guillemin, Maria Novella Piancastelli, Wayne C. Stolte, Dennis W. Lindle, Marc Simon
A New Method To Derive Electronegativity From Resonant Inelastic X-Ray Scattering, Stephane Carniato, Loic Journel, Renaud Guillemin, Maria Novella Piancastelli, Wayne C. Stolte, Dennis W. Lindle, Marc Simon
Chemistry and Biochemistry Faculty Research
Electronegativity is a well-known property of atoms and substituent groups. Because there is no direct way to measure it, establishing a useful scale for electronegativity often entails correlating it to another chemical parameter; a wide variety of methods have been proposed over the past 80 years to do just that. This work reports a new approach that connects electronegativity to a spectroscopic parameter derived from resonant inelastic x-ray scattering. The new method is demonstrated using a series of chlorine-containing compounds, focusing on the Cl 2p−1LUMO1 electronic states reached after Cl 1s→LUMO core excitation and subsequent KL radiative decay. Based on …
Thomson-Resonant Interference Effects In Elastic X-Ray Scattering Near The Cl K Edge Of Hcl, Stephane Carniato, P. Selles, Loic Journel, Renaud Guillemin, Wayne C. Stolte, L. El Khoury, T. Marin, Faris Gel'mukhanov, Dennis W. Lindle, Marc Simon
Thomson-Resonant Interference Effects In Elastic X-Ray Scattering Near The Cl K Edge Of Hcl, Stephane Carniato, P. Selles, Loic Journel, Renaud Guillemin, Wayne C. Stolte, L. El Khoury, T. Marin, Faris Gel'mukhanov, Dennis W. Lindle, Marc Simon
Chemistry and Biochemistry Faculty Research
We experimentally observed interference effects in elastic x-ray scattering from gas-phase HCl in the vicinity of the Cl K edge. Comparison to theory identifies these effects as interference effects between non-resonant elastic Thomson scattering and resonant Raman scattering. The results indicate the non-resonant Thomson and resonant Raman contributions are of comparable strength. The measurements also exhibit strong polarization dependence, allowing an easy identification of the resonant and non-resonant contributions.
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
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 …
Sulfur K-Edge Photo-Fragmentation Of Ethylene Sulfide, Wayne C. Stolte, Gunnar Ohrwall
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
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 L2 …
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
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 2px,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
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 CFnCl+ and CFn+/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
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 BaZr0.9Y0.1O2.95 (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
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.
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
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 L2,3-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 …
Design And Performance Of A Curved-Crystal X-Ray Emission Spectrometer, A. C. Hudson, Wayne C. Stolte, Dennis W. Lindle, Renaud Guillemin
Design And Performance Of A Curved-Crystal X-Ray Emission Spectrometer, A. C. Hudson, Wayne C. Stolte, Dennis W. Lindle, Renaud Guillemin
Chemistry and Biochemistry Faculty Research
A curved-crystal x-ray emission spectrometer has been designed and built to measure 2–5 keV x-ray fluorescence resulting from a core-level excitation of gas phase species. The spectrometer can rotate 180°, allowing detection of emitted x rays with variable polarization angles, and is capable of collecting spectra over a wide energy range (20 eV wide with 0.5 eV resolution at the Cl K edge) simultaneously. In addition, the entire experimental chamber can be rotated about the incident-radiation axis by nearly 360° while maintaining vacuum, permitting measurements of angular distributions of emitted x rays.
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
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.
Anion And Cation-Yield Spectroscopy Of Core-Excited Sf6, Maria Novella Piancastelli, Wayne C. Stolte, Renaud Guillemin, A. Wolska, M. M. Sant'anna, Dennis W. Lindle
Anion And Cation-Yield Spectroscopy Of Core-Excited Sf6, Maria Novella Piancastelli, Wayne C. Stolte, Renaud Guillemin, A. Wolska, M. M. Sant'anna, Dennis W. Lindle
Chemistry and Biochemistry Faculty Research
We report an extensive study on total and partial-ion-yield spectroscopy around both the S 2p and F 1s thresholds in SF6. All positive and negative single-ion channels have been measured. Below the F 1s threshold we detect a large variation in relative intensity of the resonant structures according to the specific channel monitored, indicating selective fragmentation. Above threshold, at variance with previous cases described by us, we detect high-intensity structures related to shape resonances not only in the cation channels but also for the anions. We discuss the applicability and limits of a model we …
Fragmentation Dynamics Of H2s Following S 2p Photoexcitation, Renaud Guillemin, S-W Yu, Wayne C. Stolte, Dennis W. Lindle
Fragmentation Dynamics Of H2s Following S 2p Photoexcitation, Renaud Guillemin, S-W Yu, Wayne C. Stolte, Dennis W. Lindle
Chemistry and Biochemistry Faculty Research
The fragmentation dynamics of core-excited H2S has been studied by means of partial anion and cation yield measurements around the S L2,3-subshell ionization thresholds. All detectable ionic fragments are reported, and significant differences between partial ion yields are observed. Possible dissociation pathways are discussed by comparison to previous studies of electron spectra.