Physics Commons^™

Resolving A Conflict Between Coherence Theory And Classical Radiometry, Incoherent Planar Sources Are Lambertian, Dorothy M. Seitz

Honors Capstone Projects and Theses

No abstract provided.

An Experimental Apparatus For Studying Double Differential Scattering By Low-Energy Multiply Charged Ions From Atomic Targets, Meenatchi S. Gopinathan

Masters Theses

A new differential energy-gain spectrometer with a movable parallel-plate electrostatic energy analyzer has been constructed and tested for the study of double differential (in energy and angle) cross sections for state-selective electron capture processes in collisions of low-energy multiply charged ions with atomic gases. The ion beam is produced by extracting recoil ions from a primary interaction region where these ions are generated in collisions between a neutral target gas and a fast fluorine beam from the WMU tandem Van de Graaff accelerator. An einzel lens is used to focus the ion beam extracted from the recoil-ion source into a …

Detecting Alpha Particles Through Scintillation In Porous Materials, Martin E. Keillor

Theses and Dissertations

This thesis presents the results of a preliminary study of parameters essential to the development of a scintillation flow-cell detector with improved characteristics over existing cells. Such a detector with better than 10% alpha energy resolution could provide in situ capability to detect and identify important alpha-emitting radionuclides in dilute aqueous solutions. Gel-silica is a potential candidate that may provide the needed improvement in resolution while maintaining 100% detection efficiency; however, gel-silica with useful light output is yet to be developed. As a step toward realizing the system described, the dependence of alpha detection efficiency and intrinsic energy resolution on …

Measurement Of N2+ Mobility In He Via Fourier Transform Emission Spectroscopy, Patrick D. Kee

Theses and Dissertations

Recently, Hong and Miller used Fourier Transform Emission (FTE) spectroscopy to determine the N₂⁺ mobility in helium by relating the observed Doppler shift of the N₂⁺ (B-X) transition to the measured electric field in the discharge as determined by probes. In order to establish the technique in-house, this effort duplicated that experiment and investigated the sensitivity and utility of the method. Doppler shift measurements in this experiment disagreed significantly with those reported by Hong and Miller. Attempts to reduce the data (and thus determine the mobility) using a model developed by Hong and Miller were unsuccessful. …

High Resolution Fourier Transform Spectroscopy Of The First Overtone Of The N-O Stretch In Nitrosyl Bromide, Todd E. Wiest

Theses and Dissertations

Infrared Fourier transform spectroscopy of the first overtone of the nitric oxide (NO) bond stretch in nitrosyl bromide (ONBr) has been performed at a resolution of 0.02cm^-1 to obtain the rotational parameters of the V₁ = 2 energy level. Roughly 1000 transitions have been observed for rotational levels up to J = 80 and K_a = 7. The calculation of the complete set of rotational energy levels of this asymmetric molecule requires the numerical diagonalization of four, tridiagonal matricies for each J. From a non-linear least squares fit of observed transitions with J ≤ 40 using an …

Experiment Using Infrared Spectroscopy To Study The Effect Of Soil Characteristics Upon The Rate Of Trichloroethylene Desorption, Benjamin T. Kindt

Theses and Dissertations

This research investigated the influence of soil characteristics on the desorption of trichloroethylene (TCE). TCE is one of the most common contaminants at Superfund sites. Unfortunately, extraction of TCE from contaminated soils has been hindered by its slow and poorly understood desorption from soil particles. The rate and progress of desorption of TCE from seven types of soil with varying particle diameters and elemental compositions was measured using optical absorption techniques. Fitting the data to the Langmuir Isotherm functional form predicted in the literature yielded parameters for the desorption rate and total amount desorption each soil type. These parameters were …

Use Of Infrared Spectrometry To Determine The Effect Of Temperature On The Description Rates Of Trichloroethylene From Plastic Clay 98b, Abdellatif Fares

Theses and Dissertations

This thesis investigated the influence of temperature on the desorption rated of trichloroethylene (TCE) from plastic clay. It was expected that an increase in temperature will cause an increase in both the desorption rates of TCE and in the desorbed quantity. Previous studies on other chemicals indicated a faster decrease in the remaining sorbed concentration with an increase in temperature. This research made use of the infrared optical absorption technique. IR spectroscopy was used to measure the concentration of the vapor TCE that desorbed from the soil. The soil was exposed to liquid TCE for 2 days then placed inside …

Strong Magnetic Field Effects And Molecular Processes With Applications To White Dwarfs, Phillip C. Stancil

Physics Theses & Dissertations

Radiative transitions of hydrogenlike atoms in external magnetic fields of strength applicable to magnetic white dwarfs, i.e. B < 10³ megagauss, have been investigated for field-free principal quantum numbers n < 6. Finite proton mass corrections are included. Relativistic corrections are also investigated. Transition probabilities are determined using the length, velocity, and acceleration forms of the electric dipole operator. Discrepancies between previous calculations and magnetic white dwarf observations of low-lying boundbound transitions have been studied. New results for high-lying transitions are also obtained.

The transition probability for the hydrogenlike 2s two-photon decay has been investigated and shown to increase substantially with field strength. The computed two-photon spectra show resonances and interference minima. Anomalous Zeeman depolarization features are found in computed two-photon polarization spectra of alkali atoms in laboratory strength magnetic fields. A previously observed fine structure depolarization feature is shown to decay with decreasing field strength.

Experimental Stark Shift Of Several Nii And Oii Spectral Lines, Mara Scepanovic, Vladimir Milosavljevic, Stevan Djenize, Mihajlo Platisa, Jaroslav Labat

Articles

Stark shift of four NII and seven OII spectral lines have been measured for the first time in the linear low pressure pulsed arc plasma and compared with existing theoretical values.

Tabletop X-Ray Lasers, D. C. Eder, P. Amendt, L. B. Dasilva, R. A. London, B. J. Macgowan, D. L. Matthews, B. M. Penetrante, M. D. Rosen, S. C. Silks, Thomas D. Donnelly, R. W. Falcone, G. L. Strobel

All HMC Faculty Publications and Research

Details of schemes for two tabletop size x‐ray lasers that require a high‐intensity short‐pulse driving laser are discussed. The first is based on rapid recombination following optical‐field ionization. Analytical and numerical calculations of the output properties are presented. Propagation in the confocal geometry is discussed and a solution for x‐ray lasing in Li‐like N at 247 Å is described. Since the calculated gain coefficient depends strongly on the electron temperature, the methods of calculating electron heating following field ionization are discussed. Recent experiments aimed at demonstrating lasing in H‐like Li at 135 Å are discussed along with modeling results. The …

Collisions Of Atomic Hydrogen With Oxygen, Sulfur, Sodium And Halogen Anions At Low Energies, James Anthony Fedchak

Dissertations, Theses, and Masters Projects

Total electron detachment and charge transfer cross sections, $\sigma\sb{\rm e}$(E) and $\sigma\sb{\rm ct}$(E), have been measured for collisions of the negative ions O$\sp{-}$, S$\sp{-}$, F$\sp{-}$, Cl$\sp{-}$, Br$\sp{-}$, I$\sp{-}$, Na$\sp{-}$, and K$\sp{-}$ with atomic hydrogen for laboratory energies ranging from 2 to 500 eV. For the systems F$\sp{-}$, Cl$\sp{-}$, Br$\sp{-}$, O$\sp{-}$ and S$\sp{-}$ + H, $\sigma\sb{\rm e}$(E) displays no barrier for associative detachment; the results are found to be adequately described by simple curve-crossing models based upon available intermolecular potentials, or by classical orbiting models which assume that the anion interacts with the H atom via an attractive potential of the …

Photoabsorption Spectra Of Hydrogen And Alkali Atoms In Electric Fields, Jing Gao

Dissertations, Theses, and Masters Projects

A systematic study of the photoabsorption spectra of highly excited hydrogen and alkali atoms in electric fields is presented, based on the semiclassical closed-orbit theory. In most respects, hydrogen and alkali atoms behave similarly, because the excited alkali atoms have a single electron outside of a small ionic core, and the core only produces small shifts of energy levels and small phase shifts of scattered wave functions.;For hydrogen, the classical motion of the excited electron is regular and closed orbits can be enumerated. Above the zero-field ionization threshold, the system is rather simple. There is only one closed orbit, called …

Muon Transfer From Muonic Deuterium To Carbon, David William Viel

Dissertations, Theses, and Masters Projects

Negative muons were brought to rest in a gas mixture of 30 torr CH$\sb4$ and 570 torr D$\sb2$, using the cyclotron trap at PSI. The muons formed muonic deuterium atoms which diffused through the mixture and transferred their muons to the carbon of the CH$\sb4$ molecules. A planar germanium detector and a silicon detector were used to observe x-rays from the initial muon cascade in the deuterium, and from subsequent cascade in the muonic carbon after transfer. A transfer rate of (4.5 $\pm$ 1.8) $\times$ 10$\sp{10}$/sec was found which agrees well with a previous result measured at 50 bar of …