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Articles 1 - 11 of 11

Full-Text Articles in Physics

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 Publications

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.


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.


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 ...


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 spatially separated from the flow tube, eliminating many ...


Comparison Between The Ultraviolet Emission From Pulsed Microhollow Cathode Discharges In Xenon And Argon, Isfried Petzenhauser, Leopold D. Biborosch, Uwe Ernst, Klaus Frank, Karl H. Schoenbach Jan 2003

Comparison Between The Ultraviolet Emission From Pulsed Microhollow Cathode Discharges In Xenon And Argon, Isfried Petzenhauser, Leopold D. Biborosch, Uwe Ernst, Klaus Frank, Karl H. Schoenbach

Bioelectrics Publications

We measured the dynamic I–V characteristics and vacuum ultraviolet (VUV) emission lines of the second continuum in xenon (170 nm) and argon (130.5 nm) from pulsed microhollow cathode discharges (MHCD). For pulse lengths between 1 and 100 μs the dynamic I–V characteristics are similar in both inert gases. Only the time variation of the VUV emission line at 170 nm for xenon can be related to the dimer excited states. In argon the energy transfer between the Ar*2 dimers and the oxygen impurity atoms is responsible for a qualitatively different time behavior of the resonance line ...


Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde Jan 2003

Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde

Chemistry Publications and Other Works

We present a model for the line shapes of infrared-active Q1(0) vibron bands observed in solid parahydrogen doped with low concentrations of spherical substitutional impurities. The line shapes are highly sensitive to the H2 vibrational dependence of the dopant–H2 interaction. When this vibrational dependence is strong, the dopant can trap the infrared-active vibron in its first solvation shell; in this case, the trapped vibron manifests itself in the absorption spectrum as a narrow feature to the red of the pure solid’s vibron band.


A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield Jan 2003

A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield

Chemistry Publications

Single crystals of TaAl3 were grown at high temperatures from an Al-rich, binary solution. TaAl3 adopts the D022 structure type, space group I4/mmm with a = 3.8412(5) Å, c = 8.5402(17) Å, and Z = 2. The structure type, which is the preferred structure for all group 5 trialuminides and TiAl3 as well as the high-temperature form of HfAl3, is a binary coloring of the face-centered-cubic (fcc) arrangement. The distribution of Ta atoms creates a three-dimensional network of vertex and edge-sharing square pyramids of Al atoms. Temperature-dependent electrical resistivity and magnetic susceptibility ...


The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller Jan 2003

The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

The elements Gd (99.999%; Ames Laboratory), Ta (99.999%; Ames Laboratory), and Al (99.98%; Alfa) were combined in the atomic ratio Gd6Ta4Al100 in a 2 ml alumina crucible. The crucible was placed into a fused silica tube and a second crucible, filled with SiO2 wool, was placed inverted on top of the first. The tube was sealed under 1/5 atm Ar and placed into a box furnace. The mixture was heated to 1463 K in 3 h, kept at 1463 K for 2 h, and then cooled to 1173 K over ...


Decoupling Of The Magnetic And Structural Transformations In Er5si4, Vitalij K. Pecharsky, Alexandra O. Pecharsky, Yurij Mozharivskyj, Karl A. Gschneidner Jr., Gordon J. Miller Jan 2003

Decoupling Of The Magnetic And Structural Transformations In Er5si4, Vitalij K. Pecharsky, Alexandra O. Pecharsky, Yurij Mozharivskyj, Karl A. Gschneidner Jr., Gordon J. Miller

Chemistry Publications

Er5Si4 is a member of the R5(Si4−xGex) family of alloys, where R=rare earth metal. Many of these compounds display a strong coupling between the magnetic and crystal lattices. In the naturally layered R5(Si4−xGex) materials, inter- and intralayer interactions can be controlled by chemical and physical means; thus their physical properties can be tailored within wide limits. The Er5Si4 is unique in that the temperature dependent structural sequence is opposite that of other representatives of this family. The magnetism of Er5Si4 is reflective of its exceptional place within the series.


Anisotropy And Large Magnetoresistance In The Narrow-Gap Semiconductor Fesb2, Cedomir Petrovic, J.W. Kim, Sergey L. Bud'ko, A. I. Goldman, Paul C. Canfield, Wonyoung Choe, Gordon J. Miller Jan 2003

Anisotropy And Large Magnetoresistance In The Narrow-Gap Semiconductor Fesb2, Cedomir Petrovic, J.W. Kim, Sergey L. Bud'ko, A. I. Goldman, Paul C. Canfield, Wonyoung Choe, Gordon J. Miller

Chemistry Publications

A study of the anisotropy in magnetic, transport, and magnetotransport properties of FeSb2 has been made on large single crystals grown from Sb flux. Magnetic susceptibility of FeSb2 shows diamagnetic to paramagnetic crossover around 100 K. Electrical transport along two axes is semiconducting, whereas the third axis exhibits a metal-semiconductor crossover at temperature Tcr which is sensitive to current alignment and ranges between 40 and 80 K. In H=70kOe semiconducting transport is restored for T<300K, resulting in large magnetoresistance [ρ(70kOe)−ρ(0)]/ρ(0)=2200% in the crossover temperature range.


Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde Dec 2002

Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde

Robert Hinde

We present a model for the line shapes of infrared-active Q1(0) vibron bands observed in solid parahydrogen doped with low concentrations of spherical substitutional impurities. The line shapes are highly sensitive to the H2 vibrational dependence of the dopant–H2 interaction. When this vibrational dependence is strong, the dopant can trap the infrared-active vibron in its first solvation shell; in this case, the trapped vibron manifests itself in the absorption spectrum as a narrow feature to the red of the pure solid’s vibron band.