The Gifted Child Today, Volume 11, Number 4, Issue 57

The Gifted Child Today, Volume 11, Number 4, Issue 57

Date: 1988-07/1988-08
Creator: Gold, Marvin J.; Fagerstrom, Martha; Beck, Charles; Smart, Nigel; Barber, Constance & Campbell, Sandra
Description: Table of contents and an article on the Texas Academy of Mathematics and Science by Annetta Ramsey and Rogers Redding in a volume of The Gifted Child Today, with an emphasis on college programs for gifted youngsters.
Contributing Partner: Texas Academy of Mathematics and Science
Pressure Dependence of Line Widths of Microwave Spectra of Sulphur Dioxide

Pressure Dependence of Line Widths of Microwave Spectra of Sulphur Dioxide

Date: December 1972
Creator: Yang, Wei Han
Description: Measurements of line width parameters for eleven rotational transitions of type (J -- J + 1) of SO2 were made and are reported herein. The line width quantum number (J) trend was obtained. The microwave spectrograph used for these measurements of line width is described. Operational methods to operate the spectrograph are presented and discussed, with particular attention given to how to measure the line width. Suggestions for future avenues of probing this molecule to ascertain the non-uniform behavior of the line width parameter over the quantum number and frequency range are given.
Contributing Partner: UNT Libraries
Automatic Frequency Control of Microwave Radiation Sources

Automatic Frequency Control of Microwave Radiation Sources

Date: August 1979
Creator: Payne, Bobby D.
Description: Resonant cavity controlled klystron frequency stabilization circuits and quartz-crystal oscillator frequency stabilization circuits were investigated for reflex klystrons operating at frequencies in the X-band range. The crystal oscillator circuit employed achieved better than 2 parts in 10 in frequency stability. A test of the functional properties of the frequency standard was made using the Stark effect in molecules.
Contributing Partner: UNT Libraries
Microwave Line Widths of the Asymmetric Top Formic Acid Molecule

Microwave Line Widths of the Asymmetric Top Formic Acid Molecule

Date: August 1974
Creator: Maynard, Wayne R.
Description: This work consisted of an experimental investigation of the formic acid (HCOOH) molecule's rotational spectrum. Measurements of line widths were obtained for J = 5, 12, 13, 19, and 20 for a pressure range from 1 to 10 microns. A linear behavior between Av and p was observed as predicted by theory. The line width parameter Avp was observed to depend on the quantum number J. Hard sphere collision diameters b1 were calculated using the obtained AvP values. These deduced hard sphere values were found to be larger than the physical size of the molecule. This result was found to be in general agreement with other investigation in which long range forces (dipole-dipole) dominate.
Contributing Partner: UNT Libraries
Kinetics and Mechanisms of Ligand Exchange Reactions of Chelate Complexes

Kinetics and Mechanisms of Ligand Exchange Reactions of Chelate Complexes

Date: May 1989
Creator: Cortés, José E. (José Enrique)
Description: Certain ligand substitution reactions proceed to a complete displacement of the chelate ligand. Certain reactions proceed through a mechanism involving an initial fission of the tungsten-sulfur bond to afford a coordinatively-unsaturated intermediate which is rapidly attacked by chlorobenzene. The resulting solvated intermediate establishes an equilibrium which involves desolvation-solvation. Although main group organometallic chemistry has received a great deal of attention, this discussion will be centered in organotransition metal chemistry, in particular, metal carbonyls.
Contributing Partner: UNT Libraries
An Analysis of the Perceptions of Physics Teaching Effectiveness as Viewed by Students and Physics Instructors in Universities in Thailand

An Analysis of the Perceptions of Physics Teaching Effectiveness as Viewed by Students and Physics Instructors in Universities in Thailand

Date: August 1988
Creator: Chayan Boonyaraksa
Description: The purpose of this study was to investigate the perceptions of the physics instructors, major-physics students, and nonmajor-physics students regarding actual teaching performance and effective teaching performance. The sample consisted of a total of 56 physics instructors, 120 major-physics students, and 120 nonmajor-physics students at eight public universities in Thailand. A total of 53 physics instructors or 94.64 percent, 101 major-physics students or 84.17 percent, and 107 nonmajor-physics students or 89.17 percent responded in this study. Multivariate analysis of variance, univariate analysis, one-way analysis of variance, and multiple regression were used in the follow-up assessment, with the .05 level of significance. The physics instructors, major-physics students, and nonmajor-physics students perceived actual teaching performance in class to be significantly different from effective teaching performance. The three groups rated actual teaching performance on every factor to be less than sffective teaching. There was a significant difference between the physics instructors' perceptions and the major-physics students' perceptions regarding actual teaching performance, and also there was a significant difference between the physics instructors' perceptions and the nonmajor-physics students' perceptions regarding actual teaching performance. However, there was no significant difference between major-and nonmajor-physics students' perceptions regarding actual teaching performance. There was no significant difference among ...
Contributing Partner: UNT Libraries
Dispersion of the Nonlinear Refractive Index of CS₂ in the Spectral Range of 9-11 μm

Dispersion of the Nonlinear Refractive Index of CS₂ in the Spectral Range of 9-11 μm

Date: May 1987
Creator: Mohebi, Mehrdad
Description: The nonlinear refractive index (n2) of room temperature liquid CS2 in the wavelength range of 9 to 11 micrometers is measured. A line tunable hybrid C02 TEA laser and amplifier system is used for the experiments. In these measurements the well known photoacoustic method is utilized to observe the onset of whole beam self-focusing. The photoacoustic signal in a CS2 cell, much longer than the confocal parameter, is monitored. The departure of the acoustic signal from linear growth marks the critical power for the onset of nonlinearity. It is experimentally verified that the phenomenon is power dependent as expected from self-focusing theory. The value of n2 is then calculated from the theoretical model of self focusing. Measurements of the on-axis irradiance transmitted through the nonlinear material as well as the measurements of beam distortion are used to verify the validity of the photoacoustic method. In all the measurements the on-axis intensity was smaller than the calculated threshold intensity for stimulated Brillouin scattering. The back reflection was monitored to make sure that stimulated Brillouin scattering was not playing a role in the phenomenon.
Contributing Partner: UNT Libraries
Photon Exchange Between a Pair of Nonidentical Atoms with Two Forms of Interactions

Photon Exchange Between a Pair of Nonidentical Atoms with Two Forms of Interactions

Date: May 1987
Creator: Golshan, Shahram Mohammad-Mehdi
Description: A pair of nonidentical two-level atoms, separated by a fixed distance R, interact through photon exchange. The system is described by a state vector which is assumed to be a superposition of four "essential states": (1) the first atom is excited, the second one is in the ground state, and no photon is present, (2) the first atom is in its ground state, the second one is excited, and no photon is present, (3) both atoms are in their ground states and a photon is present, and (4) both atoms are excited and a photon is also present. The system is initially in state (1). The probabilities of each atom being excited are calculated for both the minimally-coupled interaction and the multipolar interaction in the electric dipole approximation. For the minimally-coupled interaction Hamiltonian, the second atom has a probability of being instantaneously excited, so the interaction is not retarded. For the multipolar interaction Hamiltonian, the second atom is not excited before the retardation time, which agrees with special relativity. For the minimally-coupled interaction the nonphysical result occurs because the unperturbed Hamiltonian is not the energy operator in the Coulomb gauge. For the multipolar Hamiltonian in the electric dipole approximation the ...
Contributing Partner: UNT Libraries
Linear and Nonlinear Optical Techniques to Characterize Narrow Gap Semicondutors: (Hg /Cd)Te and InSb

Linear and Nonlinear Optical Techniques to Characterize Narrow Gap Semicondutors: (Hg /Cd)Te and InSb

Date: May 1986
Creator: McClure, Stephen Warren
Description: Several methods have been developed and used to characterize the narrow gap semiconductors Hg^_xCdxTe (HgCdTe) (0.20<x<0.32) and InSb both in the presence of CO2 laser radiation and in the dark. The results have allowed the determination of certain band parameters including the fundamental energy bandgap Eg which is directly related to x, the mole fraction of Cd. In the dark, characterization of several different samples of HgCdTe and InSb were carried out by analyzing the temperature dependence of the Hall coefficient and the magnetic field positions of the magnetophonon extrema from which their x-values were determined. The quality of the magnetophonon spectra is also shown to be related to the inhomogeneity Ax of the HgCdTe samples. One-photon magneto-absorption (OPMA) spectra have been obtained for x ~ 0.2 samples of p-HgCdTe thin films and n-HgCdTe bulk samples. Analysis of the OPMA transition energies allows the x-value to be determined to within « ±0.001. A method is also discussed which can be used to estimate the sample inhomogeneity Ax. Nonlinear optical properties of semiconductors are not only scientifically interesting to study, but are also proving to be technologically important as various nonlinear optical devices are being developed. One of the most valuable ...
Contributing Partner: UNT Libraries
Nonlinear Absorption Techniques and Measurements in Semiconductors

Nonlinear Absorption Techniques and Measurements in Semiconductors

Date: August 1985
Creator: Woodall, Milton Andrew
Description: We have conducted a detailed experimental and theoretical study of nonlinear absorption in semiconductors. Experimental measurements were made on a variety of materials at wavelengths of 1.06 and 0.53 microns using a picosecond Nd:YAG laser. Both two- and three-photon processes were investigated. Values of nonlinear absorption coefficients extracted from these measurements show excellent agreement with recent theory and scaling rules. Our theoretical investigation has been carried out for two-, three-,and n-photon absorption, for both continuous and pulsed sources. Expressions are obtained for the transmission of the sample in terms of the incident irradiance for each case. The physical interpretation of these results is discussed. We have also considered the effects of the photogenerated carriers on the measurements. Equations are developed that include linear absorption by these carriers. We have observed severe distortions on the transmitted beam, caused by changes in the refractive index of the material, due to the presence of these carriers. We present a model that accurately describes these effects in terms of the photogenerated carrier density. We have developed several novel techniques for monitoring nonlinear absorption. In particular, we have adapted the photoacoustic technique to the measurement of nonlinear absorption in semiconductors. We have also developed a ...
Contributing Partner: UNT Libraries
ReSource, Volume 1, Number 1, [1984]

ReSource, Volume 1, Number 1, [1984]

Date: 1984
Creator: North Texas State University
Description: ReSource magazine includes articles and notes about research at North Texas State University in various academic fields.
Contributing Partner: University Relations, Communications & Marketing department for UNT
ReSource, Volume 3, Number 1, [1986]

ReSource, Volume 3, Number 1, [1986]

Date: 1986
Creator: North Texas State University
Description: ReSource magazine includes articles and notes about research at North Texas State University in various academic fields.
Contributing Partner: University Relations, Communications & Marketing department for UNT
Microwave Spectra of ¹³C Isotopic Species of Methyl Cyanide in the Ground, v₈=1 and v₈=2 Vibrational States

Microwave Spectra of ¹³C Isotopic Species of Methyl Cyanide in the Ground, v₈=1 and v₈=2 Vibrational States

Date: May 1988
Creator: Tam, Hungsze
Description: The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.
Contributing Partner: UNT Libraries
Carbon K-Shell X-Ray and Auger-Electron Cross Sections and Fluorescence Yields for Selected Molecular Gases by 0.6 To 2 .0 MeV Proton Impact

Carbon K-Shell X-Ray and Auger-Electron Cross Sections and Fluorescence Yields for Selected Molecular Gases by 0.6 To 2 .0 MeV Proton Impact

Date: August 1986
Creator: Bhalla, Raj P. (Raj Pal), 1948
Description: Absolute K-shell x-ray cross sections and Auger-electron cross sections are measured for carbon for 0.6 to 2.0 MeV proton incident on CH₄, n-C₄H₁₀ (n-Butane), i-C₄H₁₀ (isobutane), C₆H₆ (Benzene), C₂H₂ (Acetylene), CO and CO₂. Carbon K-shell fluorescence yields are calculated from the measurements of x-ray and Auger-electron cross sections. X-ray cross sections are measured using a variable geometry end window proportional counter. An alternate method is described for the measurement of the transmission of the proportional counter window. Auger electrons are detected by using a constant transmission energy Π/4 parallel pi ate electrostatic analyzer. Absolute carbon K-shell x-ray cross sections for CH₄ are compared to the known results of Khan et al. (1965). Auger-electron cross sections for proton impact on CH₄ are compared to the known experimental values of RΦdbro et al. (1979), and to the theoretical predictions of the first Born and ECPSSR. The data is in good agreement with both the first Born and ECPSSR, and within our experimental uncertainties with the measurements of RΦdbro et al. The x-ray cross sections, Auger-electron cross sections and fluorescence yields are plotted as a function of the Pauling charge, and show significant variations. These changes in the x-ray cross sections are compared ...
Contributing Partner: UNT Libraries
K-, L-, and M-Shell X-Ray Production Cross Sections for Beryllium, Aluminum and Argon Ions Incident Upon Selected Elements

K-, L-, and M-Shell X-Ray Production Cross Sections for Beryllium, Aluminum and Argon Ions Incident Upon Selected Elements

Date: December 1986
Creator: Price, Jack Lewis
Description: Incident 0.5 to 2.5 MeV charged particle beams were used to ionize the inner-shells of selected targets and study their subsequent emission of characteristic x-rays. ⁹Be⁺ ions were used to examine K-shell x-ray production from thin F, Na, Al, Si, P, Cl, and K targets, L-shell x-ray production from thin Cu, An, Ge, Br, Zr and Ag targets, and M-shell x-ray production from thin Pr, Nd, Eu, Dy, Ho, Hf, W, Au, Pb and Bi targets. L-shell x-ray production cross sections were also measured for ²⁷Al⁺ ions incident upon Ni, Cu, Zn, As, Zr, and Pd targets. M-shell x-ray production cross sections were measure for ²⁷Al⁺ and ⁴⁰Ar⁺ ions incident upon Pr, Nd, Gd, Dy, Lu, Hf, Au, Pb, Bi, and U targets. These measurements were performed using the 2.5 MV Van de Graaff accelerator at North Texas State University. The x-rays were detected with a Si(Li) detector whose efficiency was determined by fitting a theoretical photon absorption curve to experimentally measure values. The x-ray yields were normalized to the simultaneously measured Rutherford backscattered (RBS) yields which resulted in an x-ray production cross section per incident ion. The RBS spectrum was obtained using a standard surface barrier detector calibrated for ...
Contributing Partner: UNT Libraries
ReSource, Volume 8, Number 1, Fall 1991

ReSource, Volume 8, Number 1, Fall 1991

Date: 1991
Creator: University of North Texas
Description: ReSource magazine includes articles and notes about research at University of North Texas in various academic fields.
Contributing Partner: University Relations, Communications & Marketing department for UNT