Physics Commons^™

Quenching And Rotational Energy Transfer In Molecular Bromine: Br2(B), Dean A. Massman

Theses and Dissertations

This study investigates the rotational energy transfer processes of optically excited bromine molecules in the presence of several collision partners. Resolved laser induced fluorescence spectra of collisionally populated rotational states were analyzed by means of Stern Volmer analysis. Total rotational removal rate coefficients and state-to-state rotational removal rate coefficients for the v'=11,J'=35 level of Br2(B) were obtained for collisions with Br2(X), He, Ar and Xe. Rotational removal rate coefficients were also obtained for the v'11, J'=26 and 47; v'=14, J'=36 states of Br2(B) with collisions with Ar. Total rotational removal rate for Br2 self quenching found to be 3.98+/-0.2x10-10 (cm3/Molec-Sec). …

An Erasable Optical Memory Based On Stimulated Electronic Transition Concept, James D. Satira

Electrical & Computer Engineering Theses & Dissertations

Erasable optical memory systems with a high storage density and a large data transfer rate are required for many real time data acquisition systems such as those placed aboard NASA's space born platforms. A new concept for erasable optical memory involving stimulated electronic transitions (SET) will meet these requirements. The SET concept useful in erasable optical storage systems was demonstrated in MgS and SrS doped with Eu and Sm. The optical properties of these materials were studied. The reading and writing wavelengths for these samples were determined to be 950 and 514 nm respectively. The peaks of the emission spectra …

Determination Of The Optical Properties Of Organic Thin Films By Spectroscopic Ellipsometry, Mark L. Sward

Theses and Dissertations

This thesis demonstrated the feasibility of determining the optical properties of organic and polymer thin films through the use of Spectroscopic Ellipsometry (SE). Tan Psi and cos Delta data from 300-800 nanometers (NM) were taken with a Rudolph Research s2000 spectroscopic ellipsometer four samples: indium tin oxide (ITO) coated glass; five layer poly-benzyl-L glutamate (PBLG) organic film on ITO coated glass; eight layer PBLG film on ITO coated glass; and a thiophene polymer film on a microscope slide. The data sets were fit to a choice of four computer models based on a paper written by Dwight Berreman in 1972. …

Operating Characteristics Of Xenon Gas Discharges, Michael E. Ruark

Theses and Dissertations

The voltage-current and spectral line intensity-current characteristics were measured for four Xenon gas discharges. The four discharge configurations were made up of two tubes, each examined at pressures of 1 and 10 Torr. The first tube was a hot filament tube with a 1 cm radius, and the second a cold cathode type tube of radius .3 cm. Intensity dependence upon current was primarily linear in all cases with some important deviations. The hot filament tube at 10 Torr showed a large decrease in intensity between 4 and 6 mA in the 8409 angstrom line. This is thought to be …

Energy Transfer In Singlet Oxygen And Bromine Monofluoride, Barrett F. Lowe

Theses and Dissertations

The interhalogen molecule, bromine monofluoride (BrF), is currently under study as a potential candidate for a visible chemical laser medium. Previous studies have shown a strong emission from BrF(B³π(O⁺)) in the presence of singlet oxygen. While singlet oxygen will pump BrF(X) to BrF(B), the exact mechanism is not known. Chemiluminescence observed from BrF(B) excited by oxygen in a gas flowtube was used to study the energy transfer mechanism. The objective of this research was fourfold. First, the pumping process was identified as a 3- Body Mechanism. Second, the observed vibrational distribution clearly showed the population of …

Fluorescent Lifetime Measurements Of Rare Earth Elements In Gallium Arsenide, Danny J. Topp

Theses and Dissertations

Lifetime measurements of the excited states of three GaAs semiconductors doped with the rare earth elements Erbium (ER), Praseodymium (Pr) , and Thulium (Tm) has been studied using a pulsed nitrogen laser and germanium detector. The measurements were made with an experimental set up with a system response time of 0.34 micro seconds. A 330 milliwatt nitrogen laser with a wavelength of 3370 angstrums was used to excite transitions of the rare earth elements.

Deep Level Characterization Studies In Gaas, Gordhan R. Barevadia

Electrical & Computer Engineering Theses & Dissertations

The goal of this research was to investigate deep levels in different types of GaAs, a material for high power optically controlled bulk semiconductor switches. For low resistivity semiconductors, such as silicon doped GaAs material (p =0.054 Ω cm), deep level transient spectroscopy (DLTS) was used to characterize deep levels. Three deep levels (EL6, EL3, and EL2) have been detected in this material. For high resistivity semiconductors (p > 10⁴ Ω cm), difficulty of electrical carrier injection and of making a junction does not permit the use of DLTS technique. Therefore, an experimental set-up of the photo-induced current transient spectroscopy …

An Artificial Neural Approach To The Decomposition Problem, Chandrashekar L. Masti

Electrical & Computer Engineering Theses & Dissertations

The goal of this thesis is to develop an artificial neural approach toward addressing the intractability involved with the decomposition problem. The search for the lattice of substitution property (s. p.) partitions essential to decompositions is cast into the framework of constraint satisfaction. An artificial neural network is developed to provide solutions by performing optimization of a mathematically derived objective function over the problem space. The issue of transitivity is verified to belong to a class of problems beyond the scope of solvability for conventional quadratic-order constraint satisfaction neural networks. A theorem is stated and proved establishing that third-order correlations …

Self Consistent Model Of The Glow Discharge, Hao Chen

Electrical & Computer Engineering Theses & Dissertations

The strong spatial variation of the electric field intensity in the vicinity of the cathode of a gas discharge requires the use of microscopic methods to describe the nonequilibrium behavior of the electron dynamics in this region. A one-dimensional Monte Carlo code was developed. It allows one to obtain the distribution of the electron drift velocity and rate coefficients for a given electric field intensity in the cathode fall. The results of this calculation are used to find the density distribution of charged particles in this region and consequently, by means of Poisson's equation, a corrected electric field intensity. In …

Laser Pump And Probe Excited State Absorption Measurements, Shawpin Jong

Electrical & Computer Engineering Theses & Dissertations

A pump and probe technique was used to investigate triplet-triplet excited state absorption in solutions of the scintillators 2,5 diphenyloxazole (PPO) and 2,1 naphthyl,5 phenylzole (a-NPO) in several solvents.

KrF excimer radiation (248 nm) was used to pump the samples under investigation as well as a tunable dye laser which was used as the probe. Time-resolution was obtained by changing the optical path difference between the pump and probe beams.

Transient excited state absorption was measured in a wide spectral region between 330 nm and 600 nm, showing a peak at 400 nm for PPO solutions, and two …

Measuring R And D Productivity, Richard A. Pappas, Donald S. Remer

All HMC Faculty Publications and Research

Measuring the productivity of an R&D organization is extremely tricky. Productivity is usually defined as a ratio of an output, like number of cars produced on an assembly line, to an input, like the wages paid the workers. While R&D may have a measurable input, the output is often intangible and difficult to quantify. This is further complicated because the return from an R&D department may not be realized for one or two decades,which means the time lag is much higher than in factory measurements. Furthermore, many researchers believe that this kind of measurement may be counterproductive,since the mere act …

Analysis Of Solar Collector Surface To Air Flow Thermal Transfer Using Solid State Sensors And Microcomputer Interfacing, Rudolph J. Eichenberger

Journal of the Arkansas Academy of Science

No abstract provided.

A Plasma Focus Interrupting Switch, Gregory Francis Knapp

Electrical & Computer Engineering Theses & Dissertations

The feasibility of using a dense plasma focus (DPF) as a current interrupting device has been investigated. Specifically, a 34-kJ, Mather-type DPF was modified to accept a third electrode so that a discharge could be created between this electrode and the center electrode of the DPF by a 10-kJ inductive energy storage circuit. It was anticipated that the accelerating mechanisms of the DPF pinch, which are known to cause a rapid reduction in the DPF current, would interrupt the 1-kA to 10-kA secondary discharge current thus forcing the secondary current through an external load and hence result in power amplification. …

Systematic Estimate Of Binding Energies Of Weakly Bound Diatomic Molecules, Linda L. Vahala, Mark D. Havey

Electrical & Computer Engineering Faculty Publications

There is often insufficient spectroscopic data for a full RKR inversion to yield a potential for weakly bound diatomic molecules. In these cases, parametrized functions such as the Morse or Thakkar potentials may be used to obtain estimates of the binding energy. The Thakkar potential is more flexible, and has been used successfully on some weakly bound systems. In the more usual case, the Thakkar parameter p, which determines long range behavior R^-p, is chosen by p=-a₁-1, where a₁ is the first Dunham coefficient; p is usually noninteger. The authors present …

Radiation Damage To Gaas Solar Cells Including Isotropic Effects, Larry Victor Stock

Physics Theses & Dissertations

A model is developed for the short circuit current of a GaAs solar cell due to radiation (proton or electron) induced defects in the crystal structure. This model is verified by a comparison with proton and electron irradiation results. For electron radiation and energetic protons (energy> 10 MeV), it is found that the damage in the crystal is independent of the angle of incidence. On the other hand, for lower energy proton radiation, the damage as a function of cell thickness is highly dependent on incident angle and energy. The cell's response to low energy protons is strongly dependent on …

Experiments Conducted On The Electron Beam Produced By A Dense Plasma Focus, Mark Steven Pronko

Electrical & Computer Engineering Theses & Dissertations

An experimental investigation was conducted using a 34-kJ Dense Plasma Focus (DPF) in which the possible enhancement of the electron beam was addressed. Electron beams ejected from the DPF have been observed to exceed 30 kA with pulse durations of a few nanoseconds. Enhancement was considered to be either an increase in the probability that the peak beam current exceeded some lower limit, or an increase in the mean energy of the beam electrons. The investigation was divided into two parts, each addressing one of the aspects of enhancement.

In the first part of the investigation, an axial magnetic field …

Flat Plate Solar Thermal Collectors: A Comparison Of Efficiencies Of Various Collector Configurations, Rudolph J. Eichenberger

Journal of the Arkansas Academy of Science

No abstract provided.

Effects On Electrolytic Cells Of Magnetic Fields Applied To Single Electrodes, Craig Allen Cousins

Dissertations and Theses

The primary goal of this research was to investigate the effects associated with the application of magnetic fields to single electrodes.

Picosecond Laser Pulse Irradiation Of Crystalline Silicon, K. L. Merkle, H. Baumgart, R.H. Uebbing, F. Phillipp

Electrical & Computer Engineering Faculty Publications

Morphology changes introduced by picosecond laser pulses at λ = 532 nm and 355 nm in (111) and (100) silicon samples are studied by means of optical and high-voltage electron microscopy. Depending on energy fluence, orientation and wavelength, amorphous or highly defective regions may be created. From an analysis of damage thresholds and damage depth distributions it is concluded that melting and energy confinement precedes the formation of the structural changes.

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics

Static Temperature Measurements In Supersonic Flow Using Lasar Raman Spectroscopy, Paul A. Nystrom

Mechanical & Aerospace Engineering Theses & Dissertations

Laser Raman spectroscopy is a nonintrusive technique which can generate mean static temperature (MST) data within flow fields. By ratioing two simultaneously gathered portions of the Raman scattered spectrum, absolute intensity measurements were not needed. This method was applied to a supersonic cold air jet, where the NST ranged from 160'K to 300'K. Accurate measurements were not realized due to the presence of flow contaminates, especially water vapor.

Calculated Temperature Of Grid Lateral Wires In Microwave Power Triodes, Jewell Tucker

Masters Theses & Specialist Projects

In microwave power triodes the grid drive power causes grid lateral wire heating. This development calculates the temperature of the wire as a function of the drive power, physical dimensions and characteristics of the wire material, for the following boundary conditions:

I. Constant grid drive, grid lateral wire of infinite length not connected to a heat sink.

II. Same as I except the wire is of finite length brazed to a grid frame.

III. The grid excitation in the form of pulses, and the grid lateral wire of finite length brazed to a grid frame.

the equations were verified experimentally …

Science Foundations: A Science Program For The Non-Science Student. Technical Report No. 4., James Shymansky

Educator Preparation & Leadership Faculty Works

No abstract provided.

Measurement Of Currents In Lake Mead With The Deep Water Isotopic Current Analyzer (Dwica), J. J. Sartoris, D. A. Hoffman, Bureau Of Reclamation

Publications (WR)

In Nov 1967, a Deep Water Isotopic Current Analyzer (DWICA) was used to study current patterns in the Boulder Basin of Lake Mead to determine if low-quality water from Las Vegas Bay might enter the Southern Nevada Water Project intake on Saddle Island. Secondary objectives were to study the general current patterns in Boulder Basin and the effect of power discharges at Hoover Dam on these currents. Results of current measurements at 3 stations in Boulder Basin are given. Observations indicate a definite possibility that low-quality water from Las Vegas Bay might enter the water intake on Saddle Island. Current …

Homogeneous Nucleation Of Water Vapor In Inert Gas Atmospheres, Arthur Henry Biermann

Doctoral Dissertations

"The homogeneous nucleation of water vapor in atmospheres of helium, neon, argon, krypton, and xenon was studied using an expansion type cloud chamber. A strong dependence of the nucleation rate on the particular inert carrier gas was observed. At present the only dependence upon the nature of the carrier gas included in classical nucleation theories is a small factor arising from kinetic considerations which is in the wrong direction to explain the observations. To explain the dependence of the rate on the nature of the carrier gas, a molecular cluster model is assumed allowing inert gas atoms to occupy the …

Determination Of (N, 2n) Reaction Cross-Sections For 71ga, 106cd & 138ba Using 14 Mev Neutrons, Thomas Helm

Masters Theses & Specialist Projects

The increasing trend towards the use of activation analysis as an analytic means of identifying elements and determining their relative abundance demands more accurate values of reaction cross-sections. Accurate values of cross-sections are also important in the investigation of possible shell effects in reaction mechanisms. Many activation cross-sections for reactions produced by 14 MeV neutrons have been measured because of the relative ease with which this energy of neutrons can be produced. Low voltage accelerators are capable of producing 14. MeV neutrons by the ³H( d,n)⁴He reaction. Although many people^(1-5) have measured the (n,2n) reaction cross-sections …

An Experimental And Theoretical Study Of The Nucleation Of Water Vapor On Ions In Helium And Argon, Daniel R. White

Doctoral Dissertations

"The nucleation of water vapor on ions in atmospheres of helium and argon was studied using an expansion type cloud chamber. Separation of the positive and negative ions was achieved so that the nucleation could be studied as a function of both the sign of the ionic charge and the supersaturation. A semiphenominological theory was developed as an extension of the classical theory to include the effects of the ionic charge on the nucleation process. The theoretical model of the prenucleation embryo was assumed to possess an oriented dipole surface layer with the direction of orientation dependent on the sign …

A Nonsecond Time-Of-Flight Spectometer, David Moorman

Masters Theses & Specialist Projects

The purpose of this thesis was to construct a time-of-flight spectrometer using plastic scintillators coupled to photomultiplier tubes as the primary detectors. A time-of-flight spectrometer with at least 2.0 nanoseconds of time resolution was desired.

Electrical Conductivity & Seebeck Effect In Activated Molybdenum Oxide Hydrogen Detectors, John Hooker

Masters Theses & Specialist Projects

This thesis describes the results and analysis of Seebeck coefficient and electrical conductivity measurements on "activated", molybdenum-oxide, thin film hydrogensensing elements. The work was undertaken in an effort to produce data that would be useful in obtaining an understanding of the electronic processes which cause large electrical conductivity changes in molybdenum-oxide upon exposure to small concentrations of hydrogen in air. The results are analyzed using a simple band model of a semiconductor. This model is shown to give reasonable results at high temperatures; however, a departure from the usual .! model is required in order to explain the results at …

Crossed Field Trochoidal Trajectory Devices For Investigating The Reflection Of Slow Electrons From Metallic Surfaces, Stan Lemaster

Masters Theses & Specialist Projects

The objective of this study was to build preliminary devices . which could be used to measure electron reflection coefficient values using crossed electric and magnetic fields. The technique for using crossed fields to measure reflection coefficients was developed at Air Force Cambridge Research Laboratories. The reflection coefficient is the ratio of the number of electrons in a reflected beam to the number of electrons in an incident beam striking a surface.

The work described herein was a part of a project authored by AFCRL under contract AF19 (628)-5940; Project 8605 (with Western Kentucky University being the contractor) which was …