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Articles 1 - 18 of 18
Full-Text Articles in Physics
Transition Probabilities In Kr Ii And Kr Iii Spectra, Stevan Djenize, Vladimir Milosavljevic, Milan S. Dimitrijevic
Transition Probabilities In Kr Ii And Kr Iii Spectra, Stevan Djenize, Vladimir Milosavljevic, Milan S. Dimitrijevic
Articles
On the basis of the relative line intensity ratio (RLIR) method, transition probability values of the spontaneous emission (Einstein's A values) of 14 transitions in the singly (Kr II) and 7 transitions in doubly (Kr III) ionized krypton spectra have been obtained relatively to the reference A values related to the 435.548 nm Kr II and 324.569 nm Kr III, the most intensive transitions in the Kr II and Kr III spectra. Our Kr III transition probability values are the first data obtained experimentally using the RLIR method. A linear, low–pressure, pulsed arc operated in krypton discharge was used as …
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
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.
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
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.
The Structures Of Fluorene– (H2o)1,2 Determined By Rotational Coherence Spectroscopy, David M. Laman, Alan G. Joly, Douglas Ray
The Structures Of Fluorene– (H2o)1,2 Determined By Rotational Coherence Spectroscopy, David M. Laman, Alan G. Joly, Douglas Ray
All Faculty Scholarship for the College of the Sciences
Rotational coherence spectroscopy ~RCS!, via time-correlated single photon counting, and two-color resonant two-photon ionization ~R2PI! time-of-flight mass spectrometry, have been used to characterize fluorene–(water)1,2[FL– (H2O)1,2] van der Waals clusters generated in supersonic jets. Rotational coherence traces have been obtained at excitation energies corresponding to several resonant features in the S1<-S0 R2PI spectra of FL– (H2O)1,2 . RCS simulations and diagonalization of the moment of inertia tensor have been used to obtain S1 excited state rotational constants and structures of FL– (H2O)1,2 that are consistent with …-s
Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize
Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize
Articles
On the basis of five accurately recorded neutral argon ( ) line shapes (in the 4s-5p transition) we have recovered the basic plasma parameters i.e. electron temperature ( T) and electron density ( N) using our new line deconvolution procedure in the case of three different plasmas created in a linear, low-pressure, pulsed arc discharge. The mentioned plasma parameters have also been measured using independent experimental diagnostic techniques. An excellent agreement has been found among the two sets of obtained parameters. This recommends our deconvolution procedure for plasma diagnostic purposes, especially in astrophysics where direct measurements of the …
Experimental And Calculated Stark Widths Within The Kr I Spectrum, Vladimir Milosavljevic, Stevan Djenize, Milan S. Dimitrijevic
Experimental And Calculated Stark Widths Within The Kr I Spectrum, Vladimir Milosavljevic, Stevan Djenize, Milan S. Dimitrijevic
Articles
On the basis of the precisely recorded 20 neutral krypton (Kr I) line shapes (in the 5s−5p and 5s−6p transitions), we have obtained the basic plasma parameters, i.e., electron temperature (T) and electron density (N) using our line deconvolution procedure in a plasma created in a linear, low-pressure, pulsed arc discharge operated in krypton. The mentioned plasma parameters have also been measured using independent experimental diagnostics techniques. Agreement has been found among the two sets of the obtained parameters. This recommends our deconvolution procedure for plasma diagnostical purposes, especially in astrophysics where direct measurements of the …
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
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 …
Reply To "Comment On ‘Atomic Spectral Line Free-Parameter Deconvolution Procedure’”, Vladimir Milosavljevic, Goran Poparic
Reply To "Comment On ‘Atomic Spectral Line Free-Parameter Deconvolution Procedure’”, Vladimir Milosavljevic, Goran Poparic
Articles
We do not agree with the authors of the preceding Comment [X. Nikolic, X. Ojurovic, and X. Mijatovic, Phys. Rev. E, 67, 058401, 2003]. Our numerical procedure for the deconvolution of the theoretical asymmetric convolution integral of a Gaussian and a plasma broadened spectral line profile jA,R(λ) for spectral lines enables the determination of all broadening parameters. All broadening parameters can be determined directly from the recorded line profile of a single line, with minimal assumptions or prior knowledge. Additional experimental diagnostics are not required.
Monte Carlo Simulations Of Surface Phase Transitions In A Modulated Layered Structure, Da Gao, John A. Jaszczak
Monte Carlo Simulations Of Surface Phase Transitions In A Modulated Layered Structure, Da Gao, John A. Jaszczak
Department of Physics Publications
A solid-on-solid model of a layered crystal, which has five layers per repeat period in the direction normal to the surface and with only nearest-neighbor interactions, is studied using Monte Carlo simulation to investigate the relationship between crystal structure and the corresponding surface phases. Equilibrium properties, such as the surface specific heat, interface width, and autocorrelation times, are studied as a function of temperature and system size. Results indicate three distinct surface phases exist in this model: a low-temperature flat phase, an intermediate-temperature disordered but flat phase, and a high-temperature rough phase. We suggest the possibility of introducing several intermediate …
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
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.
Ferroelectric-Field-Induced Tuning Of Magnetism In The Colossal Magnetoresistive Oxide La1Àxsrxmno3, X. Hong, A. Posadas, A. Lin, C. H. Ahn
Ferroelectric-Field-Induced Tuning Of Magnetism In The Colossal Magnetoresistive Oxide La1Àxsrxmno3, X. Hong, A. Posadas, A. Lin, C. H. Ahn
Xia Hong Publications
A ferroelectric field effect approach is presented for modulating magnetism in the colossal magnetoresistive oxide La1-xSrxMnO3 (LSMO). The ferromagnetic Curie temperature of ultrathin LSMO films was shifted by 35 K reversibly using the polarization field of the ferroelectric oxide Pb(ZrxTi1-x)O3 in a field effect structure. This shift was also observed in magnetoresistance measurements, with the maximum magnetoresistance ratio at 6 T increasing from 64% to 77%. This model system approach does not introduce substitutional disorder or structural distortion, demonstrating that regulating the carrier concentration alone changes the magnetic phase transition …
Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde
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.
An Optical Trap For Relativistic Plasma, Ping Zhang, Ned Saleh, Shouyuan Chen, Zhengming Sheng, Donald Umstadter
An Optical Trap For Relativistic Plasma, Ping Zhang, Ned Saleh, Shouyuan Chen, Zhengming Sheng, Donald Umstadter
Donald Umstadter Publications
The first optical trap capable of confining relativistic electrons, with kinetic energy <350 keV was created by the interference of spatially and temporally overlapping terawatt power, 400 fs duration laser pulses (<2.4x1018 W/cm2) in plasma. Analysis and computer simulation predicted that the plasma density was greatly modulated, reaching a peak density up to 10 times the background density (ne /n0;10) at the interference minima. Associated with this charge displacement, a direct-current electrostatic field of strength of ~2 x 1011 eV/m was excited. These predictions were confirmed experimentally by Thomson and Raman scattering diagnostics. Also confirmed were predictions that the electron density grating acted as a multi-layer mirror to transfer energy between the crossed laser beams, resulting …350>
Ferroelectricity In Free Niobium Clusters, Ramiro Moro, Xiaoshan Xu, Shuangye Yin, Walt A. De Heer
Ferroelectricity In Free Niobium Clusters, Ramiro Moro, Xiaoshan Xu, Shuangye Yin, Walt A. De Heer
Xiaoshan Xu Papers
Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [NbN; number of atoms (N) = 2 to 150, temperature (T) = 20 to 300 kelvin], measured in molecular beams, show that cold clusters may attain an anomalous component with very large electric dipole moments. In contrast, room-temperature measurements show normal metallic polarizabilities. Characteristic energies kBTG(N) [Boltzmann constant kB times a transition temperature TG(N)] are identified, below which the ferroelectric-like state develops. Generally, TG decreases [110 > TG(N) > 10K] as …
An Experimental And Theoretical Study Of Transient Negative Ions In Mg, Zn, Cd And Hg, J. P. Sullivan, Paul Burrow, D. S. Newman, K. Bartschat, J. A. Michejda, P. Panajotovic, M. Moghbelalhossein, R. P. Mceachran, Stephen J. Busckman
An Experimental And Theoretical Study Of Transient Negative Ions In Mg, Zn, Cd And Hg, J. P. Sullivan, Paul Burrow, D. S. Newman, K. Bartschat, J. A. Michejda, P. Panajotovic, M. Moghbelalhossein, R. P. Mceachran, Stephen J. Busckman
Paul Burrow Publications
A range of experimental and theoretical techniques have been applied to the study of transient negative ions (resonances) formed in electron scattering from the Group II metals Mg, Zn, Cd, and Hg at incident electron energies below the first ionization potential. A wealth of resonance structures have been observed and from the experimental observations and theoretical information, classifications are proposed for some of these negative ion states.
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Scholarship and Professional Work - LAS
We have studied effects of magnetic sublevel degeneracy on the polarization of superfluorescent pulses generated on the Ca 4s4p1P1–3d4s1D2 transition at 5.5μm. These pulses were generated from a cell of length 50 cm by optically pumping calcium vapor on the 4s21S0–4s4p1P1 transition in the presence of Ar gas. The axis of ellipticity of superfluorescence (SF) polarization is oriented parallel to the axis of the pump-laser polarization at large detunings, and undergoes an abrupt rotation through 90° for detunings close to resonance. The distribution of populations in the magnetic sublevels of the 1P1 state can be estimated using a simple model …
Coherent Backscattering Of Light In Atomic Systems: Application To Weak Localization In An Ensemble Of Cold Alkali-Metal Atoms, D. V. Kupriyanov, I. M. Sokolov, P. Kulatunga, C. I. Sukenik, M. D. Havey
Coherent Backscattering Of Light In Atomic Systems: Application To Weak Localization In An Ensemble Of Cold Alkali-Metal Atoms, D. V. Kupriyanov, I. M. Sokolov, P. Kulatunga, C. I. Sukenik, M. D. Havey
Physics Faculty Publications
Development of a theoretical treatment of multiple coherent light scattering in an ultracold atomic gas is reported. Specific application is made to coherent backscattering of a weak-radiation field from realistically modeled samples of ultracold atomic 85Rb. Comprehensive Monte Carlo simulations of the spatial, spectral, and polarization dependence of the backscattering line shape are made and compared with available experimental results.
Measurement Of Correlated Multiple Light Scattering In Utracold Atomic 85Rb, P. Kulatunga, C. I. Sukenik, S. Balik, M. D. Havey, D. V. Kupriyanov, I. M. Sokolov
Measurement Of Correlated Multiple Light Scattering In Utracold Atomic 85Rb, P. Kulatunga, C. I. Sukenik, S. Balik, M. D. Havey, D. V. Kupriyanov, I. M. Sokolov
Physics Faculty Publications
We report an experimental study of correlated multiple light scattering in an ultracold gas of 85Rb confined in a magneto-optic trap. Measurements are made of the polarization dependence of the spatial and spectral profile of light backscattered from the sample. The results show an interferometric enhancement sensitive to coherent multiple scattering in the atomic gas, and strong variations with the polarization of the incident and detected light. The spatial width and peak value of the enhancement are found to be dependent on the sample size. Comparison of all the measurements with realistic quantum Monte Carlo simulations yields a very …