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- Title
- Terrestrial Absorption in the Sodium D2 Line.
- Creator
- Lammer, Wayne E., Burnett, Clyde R., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
An experimental investigation is described in which a Pepsios high resolution pressure scanning s pectrometer is used to measure the absorption of light due to atomic sodium in the upper atmospher e. Design and construction of the spectrometer will be discussed with attention given to unique features of the instrument which were develo ped in this study. An attempt is made to see if any dependence on the abundance of the sodium can be accounted for by the proximity to the ocean or by the...
Show moreAn experimental investigation is described in which a Pepsios high resolution pressure scanning s pectrometer is used to measure the absorption of light due to atomic sodium in the upper atmospher e. Design and construction of the spectrometer will be discussed with attention given to unique features of the instrument which were develo ped in this study. An attempt is made to see if any dependence on the abundance of the sodium can be accounted for by the proximity to the ocean or by the winds and extreme turbulence developed by tropical storms and hurricanes. It is hoped that this data will compliment the existing data found at other latitudes so that a circulation dependence may be found.
Show less - Date Issued
- 1967
- PURL
- http://purl.flvc.org/fau/fd/FA00000786
- Subject Headings
- Airglow, Thermosphere, Atmosphere, Upper, Solar radiation
- Format
- Document (PDF)
- Title
- A PSEUDO-SPECTRAL EFFECT FOR THE ACOUSTIC OSCILLATIONS OF A HELIUM AFTERGLOW.
- Creator
- KILPATRICK, WALLACE DORMAN, Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The purpose of this experimental study of the helium afterglow in a hollow cathode discharge is to identify the mechanisms which cause an apparent unequal acoustic modulation of the red and violet wings of observed optical spectrum lines. The unequal red-violet effect is traceable to the fact that curved spectrum lines are formed at the exit slit of a monochromator which is equipped with straight entrance and exit slits. Curved spectrum lines emphasize the red and violet wings differently,...
Show moreThe purpose of this experimental study of the helium afterglow in a hollow cathode discharge is to identify the mechanisms which cause an apparent unequal acoustic modulation of the red and violet wings of observed optical spectrum lines. The unequal red-violet effect is traceable to the fact that curved spectrum lines are formed at the exit slit of a monochromator which is equipped with straight entrance and exit slits. Curved spectrum lines emphasize the red and violet wings differently, depending on the light contributions from different portions of the entrance slit, so that spatial variations in the optical image due to acoustic standing waves show unequal integrated light intensities for the modulation of each wing. Only the central portion of the radial standing wave in the afterglow (Bessel function J (kr) distribution) was explored, and the ratio of the red to violet amplitude calculated as 1 : 1.58 agrees qualitatively with experimental results.
Show less - Date Issued
- 1970
- PURL
- http://purl.flvc.org/fcla/dt/13423
- Subject Headings
- Helium
- Format
- Document (PDF)
- Title
- A COMPARISON OF SODIUM ABUNDANCES CALCULATED FROM DAYLIGHT ABSORPTION AND TWILIGHT EMISSION IN THE D(2) LINE.
- Creator
- LASHER, RICHARD WILLIAM, Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant...
Show moreA method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant uncertainties reveal no significant discrepancy between twilight and daytime sodium abundances.
Show less - Date Issued
- 1971
- PURL
- http://purl.flvc.org/fcla/dt/13449
- Subject Headings
- Sodium--Spectra, Absorption spectra
- Format
- Document (PDF)
- Title
- THE NECESSITY FOR A PHYSICS PROGRAM AT THE JUNIOR HIGH SCHOOL LEVEL.
- Creator
- JAROSH, STANLEY E., Florida Atlantic University, Matthews, Herman E., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
This thesis covers a brief description of current problems and the present status of physics courses at the secondary level; a review of standardized programs presently being used; and the necessity for change. The paper will show that a separate program for teaching physics should be instituted below the high school level. It will discuss a means for accomplishing this and propose how this can be done through the use of middle schools or through a change in the continuum.
- Date Issued
- 1972
- PURL
- http://purl.flvc.org/fcla/dt/13486
- Subject Headings
- Physics--Study and teaching (Secondary), Junior high schools--Curricula
- Format
- Document (PDF)
- Title
- METASTABLE EXCITATION OF POPULATION INVERSION IN A HELIUM-HYDROGEN AFTERGLOW PLASMA.
- Creator
- WOO, KING NIEN., Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A spectroscopic study of a helium-hydrogen afterglow plasma in a pulsed discharge hollow-cathode has been made to determine the energy transfer process which results in a population inversion in atomic hydrogen. Time-resolved emission measurements were made for the Balmer series in hydrogen and self-absorption measurements with lambda 3889 A (2s 3S - 3p 3P) and lambda 4650 A (2s 3sigma - 3p 3n) of helium were taken to monitor the metastable populations. Observations were made as a function of...
Show moreA spectroscopic study of a helium-hydrogen afterglow plasma in a pulsed discharge hollow-cathode has been made to determine the energy transfer process which results in a population inversion in atomic hydrogen. Time-resolved emission measurements were made for the Balmer series in hydrogen and self-absorption measurements with lambda 3889 A (2s 3S - 3p 3P) and lambda 4650 A (2s 3sigma - 3p 3n) of helium were taken to monitor the metastable populations. Observations were made as a function of impurity concentration and as a function of helium pressure. The energy transfer from the 3S atomic metastables appears highly probable with only a minor contribution from the 3sigma molecular metastables.
Show less - Date Issued
- 1975
- PURL
- http://purl.flvc.org/fcla/dt/13746
- Subject Headings
- Physics--Experiments, Energy transfer--Experiments
- Format
- Document (PDF)
- Title
- MODE-MODE COUPLING OF PLASMA WAVES IN SYSTEMS WITH STRONG NON-LINEARITIES.
- Creator
- LODDEN, JAMES ALAN, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The coupled equations of motion describing electrostatic plasma oscillations are derived using a collective coordinate approach. The boundary between the physical and nonphysical regions of phase space is discussed. The two mode case is studied in detail for both small and large initial disturbances. For small initial disturbances the motion was found to be periodic. For large initial disturbances, non-periodic growing solutions were found that approached one of two asymptotic limits. For...
Show moreThe coupled equations of motion describing electrostatic plasma oscillations are derived using a collective coordinate approach. The boundary between the physical and nonphysical regions of phase space is discussed. The two mode case is studied in detail for both small and large initial disturbances. For small initial disturbances the motion was found to be periodic. For large initial disturbances, non-periodic growing solutions were found that approached one of two asymptotic limits. For these solutions, the variables became infinitely large in a finite time.
Show less - Date Issued
- 1976
- PURL
- http://purl.flvc.org/fcla/dt/13828
- Subject Headings
- Coupled mode theory, Plasma waves
- Format
- Document (PDF)
- Title
- TRANSPORT MEASUREMENTS ON SEMICONDUCTING TCNQ SALTS.
- Creator
- LANE, JOHN EUGENE, Florida Atlantic University, Blakemore, John S., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
This work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this...
Show moreThis work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this work was the study of TCNQ charge transfer salts in which the donors were structurally related pyridinium ion radicals. Four types of donors were synthesized using a methyl or benzyl substituent along with a cyano group in the 3 or 4 position of the ring. A total of eight compounds were studied including salts of the 1:1 and 1:2 stochiometry. Compaction conductivity was measured for all eight materials along with single crystal conductivity of three of the salts.
Show less - Date Issued
- 1977
- PURL
- http://purl.flvc.org/fcla/dt/13835
- Subject Headings
- Charge transfer, One-dimensional conductors, Organic semiconductors, Salts--Electric properties
- Format
- Document (PDF)
- Title
- MEASUREMENTS OF TERRESTRIAL OH ABUNDANCES BY SPECTROSCOPIC OBSERVATION OF RESONANCE ABSORPTION OF SUNLIGHT.
- Creator
- SPERANZA, PATRICK DANIEL, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Measurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer...
Show moreMeasurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer line. Measurements of the amount of atmospheric OH absorption indicated an average vertical column abundance of (2.0 +- 0.8) (10^13) molecules/cm^2 for this observation period.
Show less - Date Issued
- 1977
- PURL
- http://purl.flvc.org/fcla/dt/13848
- Subject Headings
- Hydroxides--Absorption and adsorption, Atmospheric ozone
- Format
- Document (PDF)
- Title
- SPECTROSCOPIC MEASUREMENTS OF OH ABUNDANCES IN THE TERRESTRIAL ATMOSPHERE.
- Creator
- LANGSTON, JAMES HUTTON, II., Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Spectroscopic observations were made of the resonance absorption of sunlight by the atmospheric hydroxyl radical (OH). The abundance of 0 terrestrial OH was measured from the Fritz Peak Observatory (39.92 N, 105.50°W) in Colorado during September of 1978. These measurements were made on the absorption of the P1 (1) line of the A^2sigma^+ - x^2pi(O , O) rotational band of OH at 3081.7 A. The instrument used was the PEPSIOS (Poly Etalon Pressure Scanned Interferometric Optical Spectrometer)...
Show moreSpectroscopic observations were made of the resonance absorption of sunlight by the atmospheric hydroxyl radical (OH). The abundance of 0 terrestrial OH was measured from the Fritz Peak Observatory (39.92 N, 105.50°W) in Colorado during September of 1978. These measurements were made on the absorption of the P1 (1) line of the A^2sigma^+ - x^2pi(O , O) rotational band of OH at 3081.7 A. The instrument used was the PEPSIOS (Poly Etalon Pressure Scanned Interferometric Optical Spectrometer) because of its high luminosity - resolution product . The computer methods ·~sed in the analysis procedure are described . These measurements indicated an average daytime vertical column abundance of (5.40 ± 0.67) x 10^13 OH molecules/cm^2.
Show less - Date Issued
- 1979
- PURL
- http://purl.flvc.org/fcla/dt/13968
- Subject Headings
- Spectrum analysis, Absorption spectra, Atmospheric chemistry
- Format
- Document (PDF)
- Title
- PREDICTING FREQUENCIES AND POWER FOR A CYLINDRICAL CERENKOV SLOW WAVE STRUCTURE.
- Creator
- HOLSTEIN, DANNY GUY, Florida Atlantic University, Lamborn, Bjorn, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The dispersion relation for a dielectrically loaded cylindrical waveguide, both with and without a beam of electrons, is found. It is shown that in the limit of Cerenkov threshold, the frequency goes to infinity. Also, using the fields derived, the Poynting vector is computed. It is shown that the Poynting vector increases and the operating frequency decreases with the thickness of the liner.
- Date Issued
- 1982
- PURL
- http://purl.flvc.org/fcla/dt/14136
- Subject Headings
- Dielectric wave guides, Cherenkov radiation
- Format
- Document (PDF)
- Title
- RAMAN SPECTRA OF ZIRCONIA CERAMICS.
- Creator
- KIM, JAE HOON, Florida Atlantic University, Medina, Fernando D., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Raman spectroscopy was used to investigate how phase structure and phase stability of zirconia mixtures depend on temperature, type and concentration of added rare earth oxides, and fabrication process. All 8wt% yttria samples exhibited the tetragonal structure between 300 and 10 K. The TZP sample, prepared under pressure and fully hardened, exhibited the most completely stabilized tetragonal structure. The plasma coating process did not improve the stability of the tetragonal structure....
Show moreRaman spectroscopy was used to investigate how phase structure and phase stability of zirconia mixtures depend on temperature, type and concentration of added rare earth oxides, and fabrication process. All 8wt% yttria samples exhibited the tetragonal structure between 300 and 10 K. The TZP sample, prepared under pressure and fully hardened, exhibited the most completely stabilized tetragonal structure. The plasma coating process did not improve the stability of the tetragonal structure. Adding ceria to zirconia did not completely stabilize the tetragonal structure, while adding alumina actually destabilized it. Mode Gruneisen parameters, obtained from changes in frequency for yttria samples with different concentration, agreed with published results under pressure, except for one Eg mode. The negative value obtained for this mode was ascribed to changes in cation-anion interactions. The temperature dependence of the linewidth for this mode was quantitatively explained by cubic anharmonic interactions.
Show less - Date Issued
- 1987
- PURL
- http://purl.flvc.org/fcla/dt/14401
- Subject Headings
- Zirconium oxide, Spectrum analysis
- Format
- Document (PDF)
- Title
- A starting potential for band theory calculations generated from Thomas-Fermi theory.
- Creator
- Horvath, Eva Antoinette, Florida Atlantic University, Faulkner, J. Samuel, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The purpose of this thesis is to generate a starting potential from Thomas-Fermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic Korringa-Kohn-Rostoker band theory program. They lead to self-consistent results at a faster rate than the potentials given by Moruzzi,...
Show moreThe purpose of this thesis is to generate a starting potential from Thomas-Fermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic Korringa-Kohn-Rostoker band theory program. They lead to self-consistent results at a faster rate than the potentials given by Moruzzi, Janak, and Williams for lattice constants for which the lattice was not in equilibrium.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14487
- Subject Headings
- Energy-band theory of solids
- Format
- Document (PDF)
- Title
- The equation of state for modeling stellar core collapse.
- Creator
- Judd, David Michael, Florida Atlantic University, Bruenn, Stephen W., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A realistic equation of state is essential for accurate modeling of stellar core collapse. In this thesis, we present a derivation of the equation of state for stellar matter up to nuclear density. We begin with the lepton contribution to the equation of state. The thermodynamic equations of state for the leptons are derived from the grand potential. Two approximations for the lepton equations of state which obtain in different regimes are presented. A discussion of the computer programs that...
Show moreA realistic equation of state is essential for accurate modeling of stellar core collapse. In this thesis, we present a derivation of the equation of state for stellar matter up to nuclear density. We begin with the lepton contribution to the equation of state. The thermodynamic equations of state for the leptons are derived from the grand potential. Two approximations for the lepton equations of state which obtain in different regimes are presented. A discussion of the computer programs that were developed to calculate the solutions to these equations is included, and the results are compared with those of similar programs. A formalism is introduced for treating the nuclear component of the equation of state. The energy per baryon of nuclei at zero temperature is derived using a compressible liquid drop model. Finite temperature effects are incorporated by (1) including the thermal excitation energy, and (2) by introducing a second phase (the drip phase) of like particles (neutrons, protons, and $\alpha$-particles) that coexist with the nuclei. Equilibrium conditions for the two phases and the nuclear mass number A are derived. Expressions for the nuclear thermodynamic quantities of interest are presented.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14551
- Subject Headings
- Equations of state
- Format
- Document (PDF)
- Title
- Raman spectroscopic studies of stabilized zirconia at elevated temperatures.
- Creator
- Lacher, Nathan, Florida Atlantic University, Liu, David, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Raman spectroscopy was used to determine the phase structure and phase stability of zirconia mixtures for various elevated temperatures, type and concentration of oxides added to zirconia, and fabrication process. All 8 wt.% yttria samples showed mostly the tetragonal structure at room temperature. Three of the four 8 wt.% yttria samples exhibited the tetragonal structure at elevated temperatures, while no conclusion was inferred for the powdered sample. As compared with yttria, ceria is a...
Show moreRaman spectroscopy was used to determine the phase structure and phase stability of zirconia mixtures for various elevated temperatures, type and concentration of oxides added to zirconia, and fabrication process. All 8 wt.% yttria samples showed mostly the tetragonal structure at room temperature. Three of the four 8 wt.% yttria samples exhibited the tetragonal structure at elevated temperatures, while no conclusion was inferred for the powdered sample. As compared with yttria, ceria is a less effective stabilizer with respect to the zirconia tetragonal structure. A monoclinic transformation between 400 K and 800 K was observed in the 4 wt.% yttria sample which had been processed by rapid quenching. Adding alumina to 4 wt.% yttria did not completely stabilize the tetragonal structure at or above room temperature, making it a less effective stabilizer than yttria or ceria. The phase transformation was responsible for the unusual values in the Gr uneisen parameters obtained for the 4 wt.% yttria sample.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14589
- Subject Headings
- Zirconium oxide--Spectra, Raman spectroscopy
- Format
- Document (PDF)
- Title
- Photoemission investigation of the electronic structure in ordered and disordered copper gold.
- Creator
- Jiang, Yongjin, Florida Atlantic University, Jordan, Robin G., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The techniques of x-ray and ultra-violet photoelectron spectroscopies have been used to investigate the electronic structures in ordered (L10-structure) and disordered (fcc) CuAu. Large changes are observed in the valence band regions of the different phases, particularly in the vicinity of the Au-related states. The binding energies of the Cu-2p and Au-4f core levels in the ordered phase are shifted from the pure metal value by 0.27 +- 0.05 eV and 0.30 +- 0.05 eV, respectively. A small...
Show moreThe techniques of x-ray and ultra-violet photoelectron spectroscopies have been used to investigate the electronic structures in ordered (L10-structure) and disordered (fcc) CuAu. Large changes are observed in the valence band regions of the different phases, particularly in the vicinity of the Au-related states. The binding energies of the Cu-2p and Au-4f core levels in the ordered phase are shifted from the pure metal value by 0.27 +- 0.05 eV and 0.30 +- 0.05 eV, respectively. A small reduction of the Au-4f core level shift is found in the disordered phase. Details of the valence band structure and the shifts for the ordered phase are in accord with recently published calculations of the density of states. Investigations of the composition of the surface region using Auger electron spectroscopy indicate that there is excess Au in the surface region, in agreement with previous studies.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14702
- Subject Headings
- Photoemission, Order-disorder in alloys
- Format
- Document (PDF)
- Title
- The tight-binding coherent potential approximation embedded cluster method Monte Carlo approach and approximations to the quadratic Korringa-Kohn-Rostoker method.
- Creator
- Horvath, Eva Antoinette, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The coherent potential approximation (CPA) can yield information about the long-range characteristics of an alloy. However, since it is a single-site theory, the effect of the local environment cannot be taken into account. The CPA can be extended to more than one site using the embedded cluster method, thereby including short-range order effects. The tight-binding coherent-potential approximation embedded cluster method can be used to generate the densities of states corresponding to all...
Show moreThe coherent potential approximation (CPA) can yield information about the long-range characteristics of an alloy. However, since it is a single-site theory, the effect of the local environment cannot be taken into account. The CPA can be extended to more than one site using the embedded cluster method, thereby including short-range order effects. The tight-binding coherent-potential approximation embedded cluster method can be used to generate the densities of states corresponding to all possible configurations of any cluster, but in particular a cluster consisting of an atom and its nearest neighbors. It is then demonstrated that the interaction energies can be calculated and used in conjunction with the Monte Carlo approach to generate the phase diagram of an alloy. In addition, the formalism for two new approximations to the Quadratic Korringa-Kohn-Rostoker method is developed and is applied to a system consisting of one metal.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/12321
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- Spectroscopic studies of ZnWO4 and doped ZnWO4 single crystals.
- Creator
- Wang, Hong, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Zinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A group-theoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman...
Show moreZinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A group-theoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman spectra has been obtained experimentally in various polarization geometries. Anharmonic contributions and interactions between phonons are discussed. Photoluminescence studies of ZnWO4 (colored, color-free), ZnWO4: Nb and ZnWO4:Sb have been carried out in the temperature range from 11 to 430 K. All samples show the blue emission band. An IR emission band with a zero-phonon line (ZPL) has been found in ZnWO4 colored samples only. The lineshape function of the emission bands has been theoretically studied and compared with the experimental results. Radiative, non-radiative and multiphonon transitions have been investigated in the thermal quenching model. The temperature dependences of the intensity, the frequency and the linewidth of the ZPL have been studied. Using the Single Configurational Coordinate model, the linear coupling between electrons and phonons has been analyzed. The quadratic coupling of electrons and phonons has been studied in the Debye approximation. The coupling of electronic transitions to normal vibrational modes, pseudo-localized vibrational modes and localized modes is also discussed.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/12346
- Subject Headings
- Physics, Condensed Matter, Physics, Optics, Engineering, Materials Science
- Format
- Document (PDF)
- Title
- The electronic structure and properties of silver-magnesium alloys.
- Creator
- Liu, Yan, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The electronic structures of beta'-AgMg and Ag3Mg alloys have been investigated by a combination of photoelectron spectroscopy and first-principles band structure and photocurrent calculations. The study includes the first ever XPS and UPS measurements from the ordered and disordered phases of Ag3Mg. We concentrated mainly on measurements of the valence bands and the core level binding energies for these alloys and their parent metals. The band structures of the ordered alloys and pure metals...
Show moreThe electronic structures of beta'-AgMg and Ag3Mg alloys have been investigated by a combination of photoelectron spectroscopy and first-principles band structure and photocurrent calculations. The study includes the first ever XPS and UPS measurements from the ordered and disordered phases of Ag3Mg. We concentrated mainly on measurements of the valence bands and the core level binding energies for these alloys and their parent metals. The band structures of the ordered alloys and pure metals have been calculated by the SCF-LMTO-ASA method, and the KKR and KKRCPA calculational schemes have been used in order to determine the electronic structures of both ordered and disordered phases of Ag3Mg on an equal footing. For the purpose of interpreting the core level shifts due to alloying, a modified LMTO scheme has been applied, in a supercell geometry, to allow for relaxation effects. In addition, we have shown that the Fermi surface topology may well be an important factor in determining the relative stability of the long period superlattice structure in Ag3Mg. In general, the calculations are in very good agreement with the experimental results. We conclude that the combination of theoretical calculations and photoemission measurements provides a detailed understanding of the electronic structures and the properties of Ag-Mg alloys.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/12332
- Subject Headings
- Physics, Condensed Matter, Engineering, Metallurgy
- Format
- Document (PDF)
- Title
- The multiple scattering approach to the electronic structure of ordered solids, impurities, and alloys.
- Creator
- Wang, Yang, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
In this dissertation, multiple scattering theory (MST) plays a fundamental role. It is applied to develop the electronic structure calculation techniques for ordered solids, single impurities and binary alloys. The most accurate fast-band-theory technique based on the MST is the quadratic Korringa-Kohn-Rostoker (QKKR) method. A method for carrying out the self-consistent QKKR calculation for ordered compounds is derived and applied to palladium hydride. The application of the QKKR method to...
Show moreIn this dissertation, multiple scattering theory (MST) plays a fundamental role. It is applied to develop the electronic structure calculation techniques for ordered solids, single impurities and binary alloys. The most accurate fast-band-theory technique based on the MST is the quadratic Korringa-Kohn-Rostoker (QKKR) method. A method for carrying out the self-consistent QKKR calculation for ordered compounds is derived and applied to palladium hydride. The application of the QKKR method to single impurity problems is also examined. In order to study phase diagrams of binary alloys, a new approach, called the embedded cluster Monte Carlo (ECMC) method, is developed. It is used to calculate the miscibility gap in the Pd-Rh alloy phase diagram to an accuracy that has never before been achieved. A non-magnetic calculation for Cu-Ni alloys is also provided. These calculations required the mastery of Korringa-Kohn-Rostoker coherent-potential-approximation methods and the development of embedded cluster codes.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/12333
- Subject Headings
- Physics, Condensed Matter, Engineering, Materials Science
- Format
- Document (PDF)
- Title
- The electronic structure and properties of equi-atomic CuAu.
- Creator
- Xu, Xumou, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
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The electronic structure of equi-atomic CuAu has been investigated by a combination of photoelectron spectroscopy and first-principles band structure calculations. The study includes the first ever ARUPS and ARAES measurements from a single crystal of CuAu I. We have studied in detail the energy dispersion and shifts of a Tamm state on the (001) and (100) surfaces and we determined the surface lattice constants and the dependencies of the energy shifts on atomic concentration and geometry....
Show moreThe electronic structure of equi-atomic CuAu has been investigated by a combination of photoelectron spectroscopy and first-principles band structure calculations. The study includes the first ever ARUPS and ARAES measurements from a single crystal of CuAu I. We have studied in detail the energy dispersion and shifts of a Tamm state on the (001) and (100) surfaces and we determined the surface lattice constants and the dependencies of the energy shifts on atomic concentration and geometry. Two new surface states were found on the two surfaces and their properties have been investigated. Comparisons between the valence band spectra from the two samples of CuAu I have been carried out and the results show that the different atomic arrangements in the crystal do not have a significant effect on the band structure. We also compared spectra from the alloy with those from the parent metals. A series of calculations of the electronic structure of CuAu I has been carried out by the SCF-LMTO-ASA and RKKR methods. We found that the superzone boundaries that are created when the CuAu II phase is formed destroy appreciable regions of Fermi surface, thus, favoring the latter phase. The positions of the new boundaries are related directly to the period of the long period superlattice and we have investigated their dependence on the e/a ratio and pressure. The results are in very good agreement with previous experimental measurements. We also calculated the Fermi surfaces of three disordered Cu-Au alloys near the equi-atomic composition using the KKR-CPA scheme. The results have shown strong evidence that the Fermi surface topology may play an important role in stabilizing and determining the modulation of the LPS in CuAu II.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/12423
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)