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Articles 151 - 180 of 230

Full-Text Articles in Atomic, Molecular and Optical Physics

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 Jan 2005

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 …

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Fragmentation Dynamics Of H2s Following S 2p Photoexcitation, Renaud Guillemin, S-W Yu, Wayne C. Stolte, Dennis W. Lindle Jan 2005

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.

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Near-Edge X-Ray Absorption Fine Structure Study Of Ion-Beam-Induced Phase Transformation In Gd2(Ti1-Yzry)2o7, Ponnusamy Nachimuthu, S. Thevuthasan, V. Shutthanandan, E. M. Adams, W. J. Weber, B. D. Begg, D. K. Shuh, Dennis W. Lindle, Eric M. Gullikson, Rupert C. Perera Jan 2005

Near-Edge X-Ray Absorption Fine Structure Study Of Ion-Beam-Induced Phase Transformation In Gd2(Ti1-Yzry)2o7, Ponnusamy Nachimuthu, S. Thevuthasan, V. Shutthanandan, E. M. Adams, W. J. Weber, B. D. Begg, D. K. Shuh, Dennis W. Lindle, Eric M. Gullikson, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

The structural and electronic properties of Gd2(Ti1−yZry)2O7 (y=0–1) pyrochlores following a 2.0-MeV Au2+ ion-beam irradiation (~5.0 X 1014 Au2+/cm2) have been investigated by Ti 2p and O 1s near-edge x-ray absorption fine structure (NEXAFS). The irradiation of Gd2(Ti1−yZry)2O7 leads to the phase transformation from the ordered pyrochlore structure (Fd3m) to the defect fluorite structure (Fm3m) regardless of Zr concentration. Irradiated Gd2(Ti1−y …

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Application Of Microgels For Optical Tagging, J. Michael Carthcart, L. Andrew Lyon, Marcus Weck, Robert D. Bock Sep 2004

Application Of Microgels For Optical Tagging, J. Michael Carthcart, L. Andrew Lyon, Marcus Weck, Robert D. Bock

Biology, Chemistry, and Environmental Sciences Faculty Books and Book Chapters

In this paper we present results from our research into the use of microgel-based photonic crystals in an optical tagging application. The basis for this research is the phenomena of self-assembly of hydrogel nano- and microparticles (i.e., microgels) into colloidal crystal Bragg reflectors. Previous research has demonstrated the assembly of Bragg structures that are sensitive in the visible spectral region. This current research focuses on the extension of this process into the infrared regime and the use of these infrared-sensitive structures in the creation of an optical tag. In particular, the research effort emphasizes two primary areas: the development of …

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Nondipole Effects In The Photoionization Of Xe 4d5/2 And 4d3/2: Evidence For Quadrupole Satellites, Oliver Hemmers, Renaud Guillemin, D. Rolles, A. Wolska, Dennis W. Lindle, K. T. Cheng, W. R. Johnson, H. L. Zhou, S. T. Manson Sep 2004

Nondipole Effects In The Photoionization Of Xe 4d5/2 And 4d3/2: Evidence For Quadrupole Satellites, Oliver Hemmers, Renaud Guillemin, D. Rolles, A. Wolska, Dennis W. Lindle, K. T. Cheng, W. R. Johnson, H. L. Zhou, S. T. Manson

Environmental Studies Faculty Publications

Measurements of nondipole parameters in spin-orbit-resolved Xe 4d photoionization demonstrate dynamical differences arising from relativistic effects. The experimental data do not agree with relativistic random-phase approximation calculations of single ionization dipole and quadrupole channels. It is suggested that the discrepancy is due to the omission of multiple-excitation quadrupole channels, i.e., quadrupole satellite transitions.

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Probing Cation Antisite Disorder In Gd2ti2o7 Pyrochlore By Site-Specific Nexafs And Xps, Ponnusamy Nachimuthu, S. Thevuthasan, Mark H. Engelhard, W. J. Weber, D. K. Shuh, N. M. Hamdan, B. S. Mun, E. M. Adams, D. E. Mccready, V. Shutthanandan, Dennis W. Lindle, G. Balakrishnan, R. C. Ewing Sep 2004

Probing Cation Antisite Disorder In Gd2ti2o7 Pyrochlore By Site-Specific Nexafs And Xps, Ponnusamy Nachimuthu, S. Thevuthasan, Mark H. Engelhard, W. J. Weber, D. K. Shuh, N. M. Hamdan, B. S. Mun, E. M. Adams, D. E. Mccready, V. Shutthanandan, Dennis W. Lindle, G. Balakrishnan, R. C. Ewing

Chemistry and Biochemistry Faculty Research

Disorder in Gd2Ti2O7 is investigated by near-edge x-ray-absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti4+ ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O 1s XPS spectra obtained with a charge neutralization system from Gd2Ti2O7(100) and the Gd2Ti2O7 pyrochlore used by Chen et al. [Phys. Rev. Lett. 88, 105901 (2002)], both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for …

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Nearest-Neighbor-Atom Core-Hole Transfer In Isolated Molecules, Renaud Guillemin, Oliver Hemmers, D. Rolles, S. W. Yu, A. Wolska, I. Tran, A. C. Hudson, J. Baker, Dennis W. Lindle Jun 2004

Nearest-Neighbor-Atom Core-Hole Transfer In Isolated Molecules, Renaud Guillemin, Oliver Hemmers, D. Rolles, S. W. Yu, A. Wolska, I. Tran, A. C. Hudson, J. Baker, Dennis W. Lindle

Environmental Studies Faculty Publications

A new phenomenon sensitive only to next-door-neighbor atoms in isolated molecules is demonstrated using angle-resolved photoemission of site-selective core electrons. Evidence for this interatomic core-to-core electron interaction is observable only by measuring nondipolar angular distributions of photoelectrons. In essence, the phenomenon acts as a very fine atomic-scale sensor of nearest-neighbor elemental identity.

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Performance Characteristics Of Beamline 6.3.1 From 200 Ev To 2000 Ev At The Advanced Light Source, Ponnusamy Nachimuthu, J. H. Underwood, C. D. Kemp, Eric M. Gullikson, Dennis W. Lindle, David K. Shuh, Rupert C. Perera Jan 2004

Performance Characteristics Of Beamline 6.3.1 From 200 Ev To 2000 Ev At The Advanced Light Source, Ponnusamy Nachimuthu, J. H. Underwood, C. D. Kemp, Eric M. Gullikson, Dennis W. Lindle, David K. Shuh, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

Bend magnet beamline 6.3.1 at the Advanced Light Source operates from 200 eV to 2000 eV, primarily used for x-ray absorption fine structure investigations. The beamline optics consist of a compact, entrance-slitless, Hettrick-Underwood type variable-line-spacing plane-grating monochromator and refocusing mirrors to provide a 25 μm × 500 μm spot at the focal point in the reflectometer end station. Wavelength is scanned by the simple rotation of the grating and illuminates a fixed exit slit. The LabView based beamline control and data acquisition computer code has been implemented to provide a convenient interface to the user. The dedicated end station is …

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Dramatic Nondipole Effects In Low-Energy Photoionization: Experimental And Theoretical Study Of Xe 5s, Oliver Hemmers, Renaud Guillemin, E. P. Kanter, B. Krassig, Dennis W. Lindle, S. H. Southworth, R. Wehlitz, J. Baker, A. C. Hudson, M. Lotrakul, D. Rolles, Wayne C. Stolte, I. Tran, A. Wolska, S. Yu, M. Ya Amusia, K. T. Cheng, L. V. Chernysheva, W. R. Johnson, S. T. Manson Aug 2003

Dramatic Nondipole Effects In Low-Energy Photoionization: Experimental And Theoretical Study Of Xe 5s, Oliver Hemmers, Renaud Guillemin, E. P. Kanter, B. Krassig, Dennis W. Lindle, S. H. Southworth, R. Wehlitz, J. Baker, A. C. Hudson, M. Lotrakul, D. Rolles, Wayne C. Stolte, I. Tran, A. Wolska, S. Yu, M. Ya Amusia, K. T. Cheng, L. V. Chernysheva, W. R. Johnson, S. T. Manson

Environmental Studies Faculty Publications

The Xe 5s nondipole photoelectron parameter γ is obtained experimentally and theoretically from threshold to ∼200  eV photon energy. Significant nondipole effects are seen even in the threshold region of this valence shell photoionization. In addition, contrary to previous understanding, clear evidence of interchannel coupling among quadrupole photoionization channels is found.

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Photofragmentation Dynamics Of Core-Excited Water By Anion-Yield Spectroscopy, Wayne C. Stolte, M. M. Sant'anna, Gunnar Ohrwall, Maria Novella Piancastelli, I. Dominguez-Lopez, Dennis W. Lindle Aug 2003

Photofragmentation Dynamics Of Core-Excited Water By Anion-Yield Spectroscopy, Wayne C. Stolte, M. M. Sant'anna, Gunnar Ohrwall, Maria Novella Piancastelli, I. Dominguez-Lopez, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Partial-anion and- cation yields from H2O are presented for photon energies near the oxygen K edge. The O- yield exhibits a feature above threshold attributed to doubly excited states, in contrast to the H- and cation yields, which are nearly featureless above threshold. Additionally, the lack of the OH- fragment indicates radiative decay and provides a negligible amount of anion formation.

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E1-E2 Interference In The Vuv Photoionization Of He, E. P. Kanter, B. Krassig, S. H. Southworth, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, R. Wehlitz, M. Ya Amusia, L. V. Chernysheva, N. L. S. Martin Jul 2003

E1-E2 Interference In The Vuv Photoionization Of He, E. P. Kanter, B. Krassig, S. H. Southworth, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, R. Wehlitz, M. Ya Amusia, L. V. Chernysheva, N. L. S. Martin

Environmental Studies Faculty Publications

We have measured the forward-backward asymmetry of photoelectron angular distributions produced in the vacuum ultraviolet photoionization of helium. This asymmetry, a consequence of the breakdown of the dipole approximation, measures the real part of the ratio of the quadrupole and dipole matrix elements. In the autoionization region, the strong energy dependence of the asymmetry permits an experimental separation of the ratio of those magnitudes from their phase difference. We experimentally determined the Fano parameters of the 2p21D2 quadrupole resonance, and report improved values of the width Γ and line profile parameter q from those previously available …

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Measurement Of Proton Transfer Reaction Rates In A Microwave Cavity Discharge Flowing Afterglow, George M. Brooke Iv Apr 2003

Measurement Of Proton Transfer Reaction Rates In A Microwave Cavity Discharge Flowing Afterglow, George M. Brooke Iv

Physics Theses & Dissertations

The reaction rate coefficients between the hydronium ion and the molecules ethene (C2H4), propene (C3H6), 1-butene (C4H8) and hydrogen sulfide (H2S) were measured at 296 K. The measured reaction rates were compared to collision rates calculated using average dipole orientation (ADO) theory. Reaction efficiency depends primarily upon the proton affinity of the molecules. All the measurements were obtained using the newly developed microwave cavity discharge flowing afterglow (MCD-FA) apparatus. This device uses an Asmussen-type microwave cavity discharge ion source that is …

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Enhanced Magnetic Quantum Oscillations In The Mixed State Of A Two-Dimensional Organic Superconductor, J. Wosnitza, J. Hagel, P. J. Meeson, D. Bintley, J. A. Schlueter, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard Feb 2003

Enhanced Magnetic Quantum Oscillations In The Mixed State Of A Two-Dimensional Organic Superconductor, J. Wosnitza, J. Hagel, P. J. Meeson, D. Bintley, J. A. Schlueter, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard

Chemistry Faculty Publications and Presentations

We report on de Haas–van Alphen (dHvA) oscillations observed in the mixed state of the organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene) utilizing the field-modulation technique and torque magnetometry. At low temperatures (30 mK), the dHvA signal persists down to 1.4 T well below the upper critical field Bc2≈3.6T. Contrary to most theoretical predictions and previous experimental findings, no additional damping of the dHvA-oscillation amplitude, but a reduced damping of the dHvA signal is found. This highly unusual effect might indicate a reduced quasiparticle scattering rate or an additional oscillatory contribution in the superconducting state.

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Investigation Of The Corrosion Of Steel By Lead-Bismuth Eutectic (Lbe) Using Scanning Electron Microscopy And X-Ray Photoelectron Spectroscopy, Daniel Koury Dec 2002

Investigation Of The Corrosion Of Steel By Lead-Bismuth Eutectic (Lbe) Using Scanning Electron Microscopy And X-Ray Photoelectron Spectroscopy, Daniel Koury

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lead Bismuth Eutectic (LBE) has been proposed for use in programs for accelerator transmutation of waste. LBE is the leading candidate material as a spallation target and an option for the sub-critical blanket coolant. The corrosion of 316 and 316L stainless steels by LBE has been studied using UNLV's facilities for Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). We have compared exposed and unexposed samples and studied the differences. Some amount of surface contamination is present on the samples and has been removed by ionbeam etching. The unexposed samples reveal typical stainless steel characteristics: a chromium oxide passivation …

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Fragmentation Processes Following Core Excitation In Acetylene And Ethylene By Partial Ion Yield Spectroscopy, Maria Novella Piancastelli, Wayne C. Stolte, Gunnar Ohrwall, S-W Yu, D. Bull, K. Lantz, Alfred S. Schlachter, Dennis W. Lindle Nov 2002

Fragmentation Processes Following Core Excitation In Acetylene And Ethylene By Partial Ion Yield Spectroscopy, Maria Novella Piancastelli, Wayne C. Stolte, Gunnar Ohrwall, S-W Yu, D. Bull, K. Lantz, Alfred S. Schlachter, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Partial ion yield spectroscopy provides a very detailed picture of fragmentation processes following core excitation in isolated molecules. We exploit this potential in the analysis of decay processes following C1s→π and C1s→Rydberg excitations in ethylene and acetylene. We show that the relative intensity of spectral features related to the excitation to empty molecular orbitals or to Rydberg states is a function of the time variation of the fragmentation process. Namely, we see an intensity increase in the Rydberg states compared to the molecular orbitals as the fragmentation process becomes more extensive, a result attributable to the diffuse nature of the …

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Holographic Analysis Of Diffraction Structure Factors, S. Marchesini, N. Mannella, C. S. Fadley, M. A. Van Hove, J. J. Bucher, D. K. Shuh, L. Fabris, M. J. Press, M. W. West, Wayne C. Stolte, Z. Hussain Sep 2002

Holographic Analysis Of Diffraction Structure Factors, S. Marchesini, N. Mannella, C. S. Fadley, M. A. Van Hove, J. J. Bucher, D. K. Shuh, L. Fabris, M. J. Press, M. W. West, Wayne C. Stolte, Z. Hussain

Chemistry and Biochemistry Faculty Research

We combine the theory of inside-source/inside-detector x-ray fluorescence holography and Kossel lines/x ray standing waves in kinematic approximation to directly obtain the phases of the diffraction structure factors. The influence of Kossel lines and standing waves on holography is also discussed. We obtain partial phase determination from experimental data obtaining the sign of the real part of the structure factor for several reciprocal lattice vectors of a vanadium crystal.

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In-Situ X-Ray-Absorption Spectroscopy Study Of Hydrogen Absorption By Nickel-Magnesium Thin Films, B. Farangis, Ponnusamy Nachimuthu, T. J. Richardson, J. L. Slack, Rupert C. Perera, Eric M. Gullikson, Dennis W. Lindle, M. Rubin Jul 2002

In-Situ X-Ray-Absorption Spectroscopy Study Of Hydrogen Absorption By Nickel-Magnesium Thin Films, B. Farangis, Ponnusamy Nachimuthu, T. J. Richardson, J. L. Slack, Rupert C. Perera, Eric M. Gullikson, Dennis W. Lindle, M. Rubin

Chemistry and Biochemistry Faculty Research

Structural and electronic properties of co-sputtered Ni-Mg thin films with varying Ni to Mg ratio were studied by in-situ x-ray absorption spectroscopy in the Ni L-edge and Mg K-edge regions. Co-deposition of the metals led to increased disorder and decreased coordination around Ni and Mg compared to pure metal films. Exposure of the metallic films to hydrogen resulted in formation of hydrides and increased disorder. The presence of hydrogen as a near neighbor around Mg caused a drastic reduction in the intensities of multiple scattering resonances at higher energies. The optical switching behavior and changes in the x-ray spectra varied …

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Non-Dipolar Electron Angular Distributions From Fixed-In-Space Molecules, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, E. Shigemasa, K. Le Guen, D. Ceolin, C. Miron, N. Leclercq, P. Morin, Marc Simon, P. W. Langhoff Jul 2002

Non-Dipolar Electron Angular Distributions From Fixed-In-Space Molecules, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, E. Shigemasa, K. Le Guen, D. Ceolin, C. Miron, N. Leclercq, P. Morin, Marc Simon, P. W. Langhoff

Environmental Studies Faculty Publications

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N2. Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.

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Photoexcitation Of A Dipole-Forbidden Resonance In Helium, B. Krassig, E. P. Kanter, S. H. Southworth, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, R. Wehlitz, N. L. S. Martin May 2002

Photoexcitation Of A Dipole-Forbidden Resonance In Helium, B. Krassig, E. P. Kanter, S. H. Southworth, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, R. Wehlitz, N. L. S. Martin

Environmental Studies Faculty Publications

We have observed photoexcitation of the dipole-forbidden 1s21S0→2p21D2 resonance in helium by measuring the nondipolar forward-backward asymmetry of photoelectron angular distributions in the 2ℓ2ℓ′ autoionizing region. By exploiting the electric dipole-quadrupole interference in the excitation of both the 2s2p1P1 and 2p21D2 levels, we have observed the quadrupole resonance in photoabsorption and extracted its Fano line shape parameters and the relative phase of the 1sEp and 1sEd continua. We find the quadrupole line profile index q2 to be markedly different from theoretical expectations.

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Large Nondipole Effects In The Angular Distributions Of K-Shell Photoelectrons From Molecular Nitrogen, Oliver Hemmers, H. Wang, P. Focke, I. A. Sellin, Dennis W. Lindle, J. C. Arce, J. A. Sheehy, P. W. Langhoff Dec 2001

Large Nondipole Effects In The Angular Distributions Of K-Shell Photoelectrons From Molecular Nitrogen, Oliver Hemmers, H. Wang, P. Focke, I. A. Sellin, Dennis W. Lindle, J. C. Arce, J. A. Sheehy, P. W. Langhoff

Environmental Studies Faculty Publications

Measurements of angular distributions of K-shell electrons photoejected from molecular nitrogen are reported which reveal large deviations at relatively low photon energies ( ħω≤500eV) from emission patterns anticipated from the dipole approximation to interactions between radiation and matter. A concomitant theoretical analysis incorporating the effects of electromagnetic retardation attributes the observed large nondipole behaviors in N2 to bond-length-dependent terms in the E1⊗(E2,M1) photoelectron emission amplitudes which are indicative of a potentially universal nondipole behavior in molecular photoionization.

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Dynamical Relativistic Effects In Photoionization: Spin-Orbit-Resolved Angular Distributions Of Xenon 4d Photoelectrons Near The Cooper Minimum, H. Wang, G. Snell, Oliver Hemmers, M. M. Sant'anna, I. A. Sellin, N. Berrah, Dennis W. Lindle, P. C. Deshmukh, N. Haque, S. T. Manson Sep 2001

Dynamical Relativistic Effects In Photoionization: Spin-Orbit-Resolved Angular Distributions Of Xenon 4d Photoelectrons Near The Cooper Minimum, H. Wang, G. Snell, Oliver Hemmers, M. M. Sant'anna, I. A. Sellin, N. Berrah, Dennis W. Lindle, P. C. Deshmukh, N. Haque, S. T. Manson

Environmental Studies Faculty Publications

Two decades ago, it was predicted [Y. S. Kim et al., Phys. Rev. Lett. 46, 1326 (1981)] that relativistic effects should alter the dynamics of the photoionization process in the vicinity of Cooper minima. The present experimental and theoretical study of the angular distributions of Xe 4d3/2 and 4d5/2 photoelectrons demonstrates this effect for the first time. The results clearly imply that relativistic effects are likely to be important for intermediate- Z atoms at most energies.

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Relativistic Effects On Interchannel Coupling In Atomic Photoionization: The Photoelectron Angular Distribution Of Xe, Oliver Hemmers, S. T. Manson, M. M. Sant'anna, P. Focke, H. Wang, I. A. Sellin, Dennis W. Lindle Jul 2001

Relativistic Effects On Interchannel Coupling In Atomic Photoionization: The Photoelectron Angular Distribution Of Xe, Oliver Hemmers, S. T. Manson, M. M. Sant'anna, P. Focke, H. Wang, I. A. Sellin, Dennis W. Lindle

Environmental Studies Faculty Publications

Measurements of the photoelectron angular-distribution asymmetry parameter β for Xe 5s photoionization have been performed in the 80–200 eV photon-energy region. The results show a substantial deviation from the nonrelativistic value of β=2 and provide a clear signature of significant relativistic effects in interchannel coupling.

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Anionic Photofragmentation Of Co: A Selective Probe Of Core-Level Resonances, Wayne C. Stolte, D. L. Hansen, Maria Novella Piancastelli, I. Dominguez-Lopez, A. Rizvi, Oliver Hemmers, H. Wang, Alfred S. Schlachter, M. S. Lubell, Dennis W. Lindle May 2001

Anionic Photofragmentation Of Co: A Selective Probe Of Core-Level Resonances, Wayne C. Stolte, D. L. Hansen, Maria Novella Piancastelli, I. Dominguez-Lopez, A. Rizvi, Oliver Hemmers, H. Wang, Alfred S. Schlachter, M. S. Lubell, Dennis W. Lindle

Environmental Studies Faculty Publications

Anion-yield spectroscopy using x rays is shown to be a selective probe of molecular core-level processes, providing unique experimental verification of shape resonances. For CO, partial anion and cation yields are presented for photon energies near the C K edge. The O- yield exhibits features above threshold related only to doubly excited states, in contrast to cation yields which also exhibit pronounced structure due to the well-known σ* shape resonance. Because the shape resonance is completely suppressed for O-, anion spectroscopy thus constitutes a highly selective probe, yielding information unobtainable with absorption or electron spectroscopy.

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Interchannel Coupling In The Photoionization Of The M-Shell Of Kr Well Above Threshold: Experiment And Theory, H. S. Chakraborty, D. L. Hansen, Oliver Hemmers, P. C. Deshmukh, P. Focke, I. A. Sellin, Clemens Heske, Dennis W. Lindle, S. T. Manson Apr 2001

Interchannel Coupling In The Photoionization Of The M-Shell Of Kr Well Above Threshold: Experiment And Theory, H. S. Chakraborty, D. L. Hansen, Oliver Hemmers, P. C. Deshmukh, P. Focke, I. A. Sellin, Clemens Heske, Dennis W. Lindle, S. T. Manson

Environmental Studies Faculty Publications

Photoionization cross sections and asymmetry (β) parameters for Kr 3s, 3p, and 3d subshells have been measured and calculated in the 300–1300-eV photon energy range. Good agreement between experiment and theory is found for both cross-section branching ratios and β parameters. Interchannel coupling among the channels arising from 3s, 3p, and 3d subshells is found to be necessary for quantitative accuracy of the theory. This shows that the interchannel coupling phenomenology far above threshold, found previously for outer shells of Ne and Ar, is also operative for inner atomic shells.

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Non-Commercial Software For The Analysis And Interpretation Of High Resolution Molecular Spectra, A. R. Ford, Scott W. Reeve Jan 2001

Non-Commercial Software For The Analysis And Interpretation Of High Resolution Molecular Spectra, A. R. Ford, Scott W. Reeve

Journal of the Arkansas Academy of Science

No abstract provided.

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Synthesis Of A Ruthenium-Tetra(Tht)Dichloride Compound And The Molecular Structure Of The Partially Oxidized Compound Rucl2(Tht)2.2(Tht-O)1.8, L. A. Thornton, Mark Draganjac, Andres Meza, A. W. Cordes Jan 2001

Synthesis Of A Ruthenium-Tetra(Tht)Dichloride Compound And The Molecular Structure Of The Partially Oxidized Compound Rucl2(Tht)2.2(Tht-O)1.8, L. A. Thornton, Mark Draganjac, Andres Meza, A. W. Cordes

Journal of the Arkansas Academy of Science

No abstract provided.

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Synthesis And Characterization Of A Ruthenium-Thioxane Complex, Amanda Wroble, Scotty Sproles, Mark Draganjac, Paul M. Nave Jan 2001

Synthesis And Characterization Of A Ruthenium-Thioxane Complex, Amanda Wroble, Scotty Sproles, Mark Draganjac, Paul M. Nave

Journal of the Arkansas Academy of Science

No abstract provided.

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Development Of Solid State Uv Detector Using Commercial Tld And Ln2o3:Re3+ (Ln=Y, La, Gd; Re=Tm, Tb, Eu, Er, Pr), Abdullah Mohd. Noh Jan 2001

Development Of Solid State Uv Detector Using Commercial Tld And Ln2o3:Re3+ (Ln=Y, La, Gd; Re=Tm, Tb, Eu, Er, Pr), Abdullah Mohd. Noh

Student Works (2000-2009)

Dosimetry of terrestrial ultraviolet (UV) using thermoluminescence (TL) material is an attractive method for a number of reasons. Such as the low cost per phosphor, the possibility to produce them in laboratory with simple facilities, the absence of any associated electronics at the site of measurement and the small size of solid phosphors which can also be used in personal dosimetry. In this research, we are searching for a suitable lanthanide oxide powder and commercial TLD material that can detect solar UV radiation using intrinsic method. The investigated lanthanide oxide powders include Gd₂O₃, La₂O₃ and Y₂O₃ doped with different rare …

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Photoelectron Spectroscopy And The Dipole Approximation, Oliver Hemmers, Dennis W. Lindle Jan 2001

Photoelectron Spectroscopy And The Dipole Approximation, Oliver Hemmers, Dennis W. Lindle

Environmental Studies Faculty Publications

Over the past three decades, the dipole approximation has facilitated a basic understanding of the photoionization process in atoms and molecules. Advances in gas-phase photoemission experiments using synchrotron radiation have recently highlighted nondipole effects at relatively low photon energies while probing the limits of the dipole approximation. Breakdowns in this approximation are manifested primarily as deviations from dipolar angular distributions of photoelectrons. Detailed new results demonstrate nondipolar angular-distribution effects are easily observable in atomic gases at energies well below 1 keV, and, in molecules, a previously unexpected phenomenon greatly enhances the breakdown of the dipole approximation just above the core-level …

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Electric-Octupole And Pure-Electric-Quadrupole Effects In Soft X-Ray Photoemission, Andrei Derevianko, Oliver Hemmers, S. Oblad, P. Glans, H. Wang, S. B. Whitfield, R. Wehlitz, I. A. Sellin, W. R. Johnson, Dennis W. Lindle Mar 2000

Electric-Octupole And Pure-Electric-Quadrupole Effects In Soft X-Ray Photoemission, Andrei Derevianko, Oliver Hemmers, S. Oblad, P. Glans, H. Wang, S. B. Whitfield, R. Wehlitz, I. A. Sellin, W. R. Johnson, Dennis W. Lindle

Environmental Studies Faculty Publications

Second-order [O(k2), k = ω/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100–1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms. Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.

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