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1995

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Articles 1 - 28 of 28

Full-Text Articles in Atomic, Molecular and Optical Physics

Measured Stark Widths Of A 425,94 Nm Ari Spectral Line, Ljiljana Skuljan, Vladimir Milosavljevic, Aleksandar Sreckovic, Stevan Djenize Dec 1995

Measured Stark Widths Of A 425,94 Nm Ari Spectral Line, Ljiljana Skuljan, Vladimir Milosavljevic, Aleksandar Sreckovic, Stevan Djenize

Articles

No abstract provided.

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Study Of The Long-Term Desorption Of Trichloroethylene From Clay Soils Using Infrared Spectroscopy, Mary P. Stager Dec 1995

Study Of The Long-Term Desorption Of Trichloroethylene From Clay Soils Using Infrared Spectroscopy, Mary P. Stager

Theses and Dissertations

Slow desorption of contaminants from soil presents one of the greatest challenges to modeling contaminant fate and transport and implementing effective remediation technologies. The kinetics of long-term desorption of trichloroethylene (TCE) from powdered clay soils were studied to determine the desorption rates and mechanism. Infrared absorption spectroscopy was used to monitor the concentration of TCE desorbed from contaminated flint clay for 71 hours. Observed gas phase TCE concentrations as a function of time were compared to that predicted by a one-site Langmuir desorption mechanism. The Langmuir model, with a single type of bonding site, did not account for the release …

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A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson Dec 1995

A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson

Theses and Dissertations

The Millimeter-wave Atmospheric Sounder (MAS) is a high resolution limb- scanning microwave radiometer-spectrometer which has been flown aboard the Space Shuttle. The instrument was designed to sense the microwave emission from several upper atmospheric constituents, including water vapor and ozone. The resonant frequencies of water vapor and ozone are extremely close (183 and 184 GHz, respectively), so that the high-frequency wing of the water vapor spectrum overlaps the low frequency wing of the ozone spectrum. Consequently, the measured ozone spectrum incorporates a slight water vapor contribution; therefore, the retrieved ozone profile is dependent on the true water vapor profile. The …

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A Portable Compton Gamma-Ray Camera Design, Brian L. Evans Dec 1995

A Portable Compton Gamma-Ray Camera Design, Brian L. Evans

Theses and Dissertations

The purpose of this research is to investigate the angular resolution, efficiency, and energy resolution possible from a portable Compton camera gamma ray imaging system for possible use in the field of nuclear nonproliferation. The proposed device uses room temperature semiconductor and position sensitive scintillation detectors. The position and energy resolution (and their energy dependence) of a room temperature lithium drifted silicon (Si(Li)) detector and a position sensitive thallium -doped sodium iodide (NaI(Tl)) scintillation detector are investigated. The position and energy resolution of the position sensitive scintillation detector is also modeled computationally, and the results compared to measured data. An …

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Steady-State Kinetics Of Br(2P1/2) Yields Co2(101) Electronic-To-Vibrational Energy Transfer Laser System, Stephen J. Karis Nov 1995

Steady-State Kinetics Of Br(2P1/2) Yields Co2(101) Electronic-To-Vibrational Energy Transfer Laser System, Stephen J. Karis

Theses and Dissertations

Steady state photolysis experiments were conducted to gain information relevant to the construction of a continuous wave electronic to vibrational pumped infrared laser. An Ar+ laser =488 µm) was used to produce the electronically excited state Br(2P1/2) (Br*) via photolysis of molecular bromine. Energy was then transferred to the near resonant vibrational state CO2(101) (CO2) via the collisional quenching of Br* by CO2. The dependence of the 2.71 µm Br* and 4.3 µm CO2 emissions on CO2 pressure was measured, as well as …

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Strong X-Ray Emission From High-Temperature Plasmas Produced By Intense Irradiation Of Clusters, T. Ditmire, Thomas D. Donnelly, R. W. Falcone, M. D. Perry Oct 1995

Strong X-Ray Emission From High-Temperature Plasmas Produced By Intense Irradiation Of Clusters, T. Ditmire, Thomas D. Donnelly, R. W. Falcone, M. D. Perry

All HMC Faculty Publications and Research

The interaction of an intense laser pulse with large (∼100Å) clusters present in pulsed gas jets is shown to produce novel plasmas with electron temperatures far in excess of that predicted by above-threshold ionization theory. The enhanced absorption of the laser light by the dense clusters results in the production of high ion charge states via collisional ionization resulting in strong x-ray emission from the hot plasma.

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Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak Sep 1995

Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak

Theses and Dissertations

The material parameters and crystalline quality of undoped, MBE-grown InAs1-xSbx nearly lattice-matched to (100) GaSb (-0.617% ≤ Δ a-a ≤ +0.708%) similar to material used for mid-infrared semiconductor lasers were determined by optical characterization. Absorption measurements at temperatures between 6-295 K determined the energy gap and wavelength-dependent absorption coefficient for each sample. The compositional dependence of the energy gap was anomalous when compared to previously reported data, suggesting phase separation existed in the material. The samples were also studied by temperature- and excitation-dependent photoluminescence (PL), which, for the majority of cases, showed only a single band-edge peak, …

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Collisional Dynamics Of The Rubidium 52P Levels, Matthew D. Rotondaro Sep 1995

Collisional Dynamics Of The Rubidium 52P Levels, Matthew D. Rotondaro

Theses and Dissertations

The collisional dynamics of the 52P levels in rubidium has been examined using steady-state laser absorption and spectrally-resolved laser induced fluorescence techniques. State-to-state cross-sections for energy transfer between Zeeman split levels ranged from 16-248 °A2 for collisions with nitrogen and rare gases. These energy transfer cross-sections exhibit a significant dependence on (J,mj) state and certain symmetry relationships are demonstrated. A sub-Doppler spectrum of the Zeeman split levels indicating the isotopic shift in the D1 line of 106 ± 35 was obtained using laser saturation spectroscopy.

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Non-Imaging Infrared Spectral Target Detection, Matthew R. Whiteley Sep 1995

Non-Imaging Infrared Spectral Target Detection, Matthew R. Whiteley

Theses and Dissertations

Automatic detection of time-critical mobile targets using spectral-only infrared radiance data is explored. A quantification of the probability of detection, false alarm rate, and total error rate associated with this detection process is provided. A set of classification features is developed for the spectral data, and these features are utilized in a Bayesian classifier singly and in combination to provide target detection. The results of this processing are presented and sensitivity of the class separability to target set, target configuration, diurnal variations, mean contrast, and ambient temperature estimation errors is explored. This work introduces the concept of atmospheric normalization of …

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Angle-Resolved Photoelectron Spectroscopy Of C60, T. Liebsch, O. Plotzke, Franz Heiser, U. Hergenhahn, Oliver Hemmers, R. Wehlitz, J. Viefhaus, B. Langer, S. B. Whitfield, U. Becker Jul 1995

Angle-Resolved Photoelectron Spectroscopy Of C60, T. Liebsch, O. Plotzke, Franz Heiser, U. Hergenhahn, Oliver Hemmers, R. Wehlitz, J. Viefhaus, B. Langer, S. B. Whitfield, U. Becker

Environmental Studies Faculty Publications

Angle-resolved photoelectron spectra of gaseous C60 were recorded in the photon energy regions from 21 to 108 eV and from 295 to 320 eV. Partial cross sections σ and the angular distribution anisotropy parameter β vary significantly with photon energy, particularly in the near-threshold region of the valence and the core ionization regimes. Some of these effects may be attributed to scattering of the outgoing photoelectron by the atoms of the ionized C60 molecule. Our results indicate that the observed satellites of the C(1s) main line are most likely of shake-up character. Low-energy electrons emitted below the shake-off …

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Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii Jul 1995

Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii

Theses and Dissertations

The p-channel In0.52Al0.48As-GaAs1-xSbx heterostructure insulated-gate field effect transistor (p-HIGFET) is a candidate for complementary integrated circuits due to superior cutoff characteristics and low gate leakage current. Advancement of the In0.52Al0.48As-GaAs1-xSbx p-HIGFET requires improved source-drain design. Five main tasks were accomplished to achieve this goal. First, thermal limits of the In0.52Al0.48As-GaAs0.51Sb0.49 HIGFET were investigated. Second, the temperature dependence of band gap and impurity energies were determined for beryllium doped In0.52Al0.48. Third, high acceptor concentrations were obtained …

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Vibrational-State-Dependent Decay Of The Co C(1s) Excitation, N. Saito, Franz Heiser, Oliver Hemmers, A. Hempelmann, K. Wieliczek, J. Viefhaus, U. Becker Jun 1995

Vibrational-State-Dependent Decay Of The Co C(1s) Excitation, N. Saito, Franz Heiser, Oliver Hemmers, A. Hempelmann, K. Wieliczek, J. Viefhaus, U. Becker

Environmental Studies Faculty Publications

Molecular ionization and ionic fragmentation of core excited CO valence and Rydberg states are studied by partial-ion-yield spectroscopy at vibrational resolution. The vibrational intensities of the Rydberg excitations differ significantly depending on the ionization and/or fragmentation channel. The observed intensity variations are explained by nondissociative excited final ionic states of the subsequent molecular Auger decay. The vibrational levels of these final states become selectively depopulated due to interaction with dissociative decay channels leading to ionic fragmentation.

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Bandwidth And Additive Bandwidth Of Graphs, Maria Kujawski May 1995

Bandwidth And Additive Bandwidth Of Graphs, Maria Kujawski

Honors Capstone Projects and Theses

No abstract provided.

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Dynamics Of Optical-Field-Ionized Plasmas For X-Ray Lasers, Thomas D. Donnelly, R. W. Lee, R. W. Falcone Apr 1995

Dynamics Of Optical-Field-Ionized Plasmas For X-Ray Lasers, Thomas D. Donnelly, R. W. Lee, R. W. Falcone

All HMC Faculty Publications and Research

The success of recombination-pumped x-ray laser schemes is determined by the kinetics of ions in plasmas with relatively dense, cold-electron distributions. We examine how laser gain in such systems is affected by a multipeaked electron distribution generated by sequential ionization of atoms using high-intensity, ultrashort-pulse lasers. We also investigate the role of heating processes that modify electron energy distributions during the recombination and the accompanying collisional cascade. We find that conditions for the success of these schemes are critically modified by the inclusion of these effects.

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Measurement Of Hyperfine Coupling Constants Of The 5d²D₃/₂ And 5d²D₅/₂ Levels In Atomic Cesium Using Polarization Quantum Beat Spectroscopy, Wo Yei Apr 1995

Measurement Of Hyperfine Coupling Constants Of The 5d²D₃/₂ And 5d²D₅/₂ Levels In Atomic Cesium Using Polarization Quantum Beat Spectroscopy, Wo Yei

Physics Theses & Dissertations

Accurate measurements of hyperfine constants have revealed effects that can not be explained by a simple hydrogenic picture of the alkali atoms such as cesium [1-3]. More precise experimental results and theoretical treatments are in demand for the alkali elements, especially for atomic cesium because of its wide range of applications. Therefore, it is essential to understand its atomic and nuclear structure. Precision measurement of its excited-states properties such as hyperfine structure provides global information on nuclear charge and current distributions and also serves as a check to the theory and a calibration of calculated excited state wave functions. Accurate …

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Excited-State Magnesium-Rare Gas Optical Collisions, Rosemary A. Lasell Apr 1995

Excited-State Magnesium-Rare Gas Optical Collisions, Rosemary A. Lasell

Physics Theses & Dissertations

Polarization and intensity spectra have been obtained for excited-state magnesium (3s3p 1P1) - rare gas optical collisions. The magnesium was excited by a linearly polarized laser tuned to the 3s21s0 → 3s3p 1P1 atomic transition at 285 nm. A second linearly polarized laser was tuned near the 3s3p 1P1 → 3s5s 1S0 transition at 571 nm (experiment A) and near the 3s3p 1P1 → 3s4d 1D2 transition at 553 nm (experiment B). The polarization vector of the second laser was oriented either parallel or …

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Statistical Properties Of Schriidinger Real And Imaginary Cat States, Victor V. Dodonov, Serguei Y. Kalmykov, Vladimir I. Man'ko Mar 1995

Statistical Properties Of Schriidinger Real And Imaginary Cat States, Victor V. Dodonov, Serguei Y. Kalmykov, Vladimir I. Man'ko

Serge Youri Kalmykov

We study the photon statistics in the superpositions of coherent states |\alpha> and |\alpha*> named “Schroedinger real and imaginary cat states”. The oscillatory character of the photon distribution function (PDF) emerging due to the quantum interference between the two components is shown, and quadrature squeezing is observed for moderate values |\alpha| ~ 1. In spite of the quantity <\delta n^2> / tending to unity (like in the Poissonian PDF) at |\alpha| >> 1, the photon statistics is essentially non-Poissonian for all values of |\alpha|. The factorial moments and cumulants of the PDF are calculated, and oscillations of their ratio are demonstrated.

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Observation Of Parity-Unfavored Transitions In The Nonresonant Photoionization Of Argon, B. Langer, J. Viefhaus, Oliver Hemmers, A. Menzel, R. Wehlitz, U. Becker Feb 1995

Observation Of Parity-Unfavored Transitions In The Nonresonant Photoionization Of Argon, B. Langer, J. Viefhaus, Oliver Hemmers, A. Menzel, R. Wehlitz, U. Becker

Environmental Studies Faculty Publications

Single-photon ionization of an atom or molecule can be subdivided into parity-favored and -unfavored transitions, the latter characterized by electron emission, preferentially perpendicular to the electric vector. The nonresonant existence of these transitions is shown experimentally and studied over an extended energy range for a variety of satellite transitions in atomic argon. The spectra exhibit several clearly resolved satellite lines with strongly negative β values close to -1, independent of the photon energy. The results confirm the corresponding predictions of angular-momentum transfer theory.

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Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera Feb 1995

Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

A new “Cowan type” double-crystal monochromator, based on the boomerang design used at National Synchrotron Light Source (NSLS) beamline X-24A, has been developed for beamline 9.3.1 at the Advanced Light Source (ALS), a windowless ultrahigh vacuum beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design of the monochromator has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline …

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High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle Feb 1995

High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1-6 keV photon-energy range, designed to achieve the goals of high energy resolution, high flux, and high brightness at the sample. When completed later this year, it will be the first ALS monochromatic hard-x-ray beamline, and its brightness will be an order-of-magnitude higher than presently available in this energy range. In addition, it will provide flux and resolution comparable to any other beamline now in operation. To achieve these goals, two technical improvements, relative to existing x-ray beamlines, were incorporated. First, a somewhat novel optical design …

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Implications Of Fumi’S Theorem For Auxiliary Particle Methods, S. E. Barnes Jan 1995

Implications Of Fumi’S Theorem For Auxiliary Particle Methods, S. E. Barnes

Physics Articles and Papers

Fumi’s theorem in conjunction with some general theorems associated with auxiliary particle methods dictates the functional form of the on-shell auxiliary particle self-energy Σ for a certain class of impurity scattering problems. An explicit calculation which confirms the result is described and the implications for various approaches to the Kondo effect discussed.

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Alpha+28si Cluster Structure As Solitons On The Nuclear Surface, Andrei Ludu Jan 1995

Alpha+28si Cluster Structure As Solitons On The Nuclear Surface, Andrei Ludu

Andrei Ludu

No abstract provided.

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Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu Jan 1995

Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu

Electrical & Computer Engineering Faculty Publications

Scanning-tunneling microscopy has been used to study temperature and coverage dependence of the structure of lead on the Si(111)-7×7 surface. For low Pb coverage, the Pb atoms favored the faulted sites. The ratio between the number of Pb atoms on faulted to unfaulted sites increased after sample annealing. An energy difference of 0.05 eV associated with a Pb atom on these two sites is estimated. The mobility of Pb atoms on Si(111) was observed at a temperature as low as 260°C for a coverage of 0.1 and 1 ML. © 1995 The American Physical Society.

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Femtosecond Laser-Produced Plasma X-Rays From Periodically Modulated Surface Targets, J. C. Gautheir, S. Bastiani, P. Audebert, J. P. Geindre, K. Neuman, Thomas D. Donnelly, M. Hoffer, R. W. Falcone, R. Shepherd, D. Price, B. White Jan 1995

Femtosecond Laser-Produced Plasma X-Rays From Periodically Modulated Surface Targets, J. C. Gautheir, S. Bastiani, P. Audebert, J. P. Geindre, K. Neuman, Thomas D. Donnelly, M. Hoffer, R. W. Falcone, R. Shepherd, D. Price, B. White

All HMC Faculty Publications and Research

We have studied theoretically and experimentally the x-ray production above 1 keV from femtosecond laser plasmas generated on periodically modulated surface targets. Laser energy coupling to plasma surface waves has been modeled using a numerical differential method. Almost total absorption of incident laser radiation is predicted for optimized interaction conditions. Silicon gratings have been irradiated by a 120fs Ti:sapphire laser at irradiances in excess of 1016 W/cm2. X-ray intensities above 1.5 keV (K-shell lines) have been measured as a function of the incidence angle. Results show a distinct x-ray emission maximum for the first order diffraction …

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Critical Energy Of Torus Knots, Fred Hickling, Wesley Davis, Heather Woolverton Jan 1995

Critical Energy Of Torus Knots, Fred Hickling, Wesley Davis, Heather Woolverton

Journal of the Arkansas Academy of Science

The energy of a smoothly parameterized knot y(t) is defined as rr\ i i lp7 \\dn dsdt Jo Jo \||7M-7(0f (D(t(s),T(t))) 2 j\\ds \\dt where D(y (s), y(t)) is the arc length between the two points y (s) and y(t) on the curve. Simple calculus based arguments are used to locate critical values of the energy functional for torus knots. Explicitly the curves given parametrically by °(«*)W = (V2°iSri).JSSBe V2 C s7nS are CriticalP ° intS ° fthe energy functional whenever a and b are relatively prime.

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Theoretical Investigation Of Two-Color, Two-Photon, 6s(2)S(1/2) → 5d(2)D(J) → 11p(2)P(3/2) Excitation And Depolarization Spectra In Atomic Cesium, Boris Dobrydnev Jan 1995

Theoretical Investigation Of Two-Color, Two-Photon, 6s(2)S(1/2) → 5d(2)D(J) → 11p(2)P(3/2) Excitation And Depolarization Spectra In Atomic Cesium, Boris Dobrydnev

Physics Theses & Dissertations

The theoretical investigation of two-photon, two-color intensity and depolarization spectra for the 6s2S1/2 → 5d2Dj → 11p2P3/2 transition in atomic caesium is considered. For quadrupole-dipole transitions the dependence of excitation from the ratio of reduced matrix elements is shown. The experimental method of determination of the value and sign of the ratio is proposed. Comparison of results for co- and counterpropagating beams revealed the strong dependence of the transition rate on the relative beam directions. Analysis of the influence of the external electric field on the process of absorption is presented. …

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Precision Measurement Of Relative Dipole Matrix Elements In Atomic Sodium, Rodney P. Meyer Jan 1995

Precision Measurement Of Relative Dipole Matrix Elements In Atomic Sodium, Rodney P. Meyer

Physics Theses & Dissertations

Relative dipole matrix elements are measured by means of a new spectroscopic technique called polarization interference spectroscopy. It is a two-color two-photon nonresonant process that maps the matrix elements into the energy domain by means of quantum mechanical interference. The technique measures the relative magnitude of the reduced matrix elements, particularly those involving excited states, to accuracies that are an order of magnitude better than previously available. Also, for the first time the relative phase of the reduced matrix elements is measured. The ratio of reduced matrix elements for the transitions 3s 2S1/2 →3P 2P3/2 →5s …

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Search For Metastability Of 2s Muonic Neon, Bernard Wilhelm Bach Jan 1995

Search For Metastability Of 2s Muonic Neon, Bernard Wilhelm Bach

Dissertations, Theses, and Masters Projects

An experiment was performed at the Paul Scherrer Institut (PSI) to establish the conditions for the metastability of the 2S-state of muonic neon. The muonic atoms were formed by stopping negative muons in the neon-filled target chamber of the PSI cyclotron trap. A pair of intrinsic germanium detectors were used in coincidence to search for the two photon decay of the 2S-state. Both energy and time information from two photon events were written to disk for off-line analysis. Data were accumulated for neon pressures of 40 and 400 Torr. The data were then searched for evidence of two photon transitions …

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