Physical Sciences and Mathematics Commons^™

Mössbauer Studies Of Electrostatic Hyperfine Interactions In 238U, 236U, And 234U, Joyce Anne Monard

Doctoral Dissertations

The nuclear gamma resonance (NGR) for ²³⁸U, ²³⁶U, and ²³⁴U in the compound (UO₂) Rb (NO₃)₃ has been established at 4.2°K following the alpha decay of PuO₂ sources. The ratios of the electric quadrupole moments of these isotopes have been determined and the electric field gradient at the uranium site has been calculated from the data. The isomer shift in ²³⁴U has been measured for both PuO₂ and PuA1₄ sources and the change in nuclear radius between the excited and the ground state has been calculated.

A Study Of The (3He, N) Reaction At 25 Mev, Mark Bentley Greenfield

Doctoral Dissertations

Energy spectra of neutrons from the ¹²C (³He, n)140; ²⁷A1(³He, n)²⁹P; ²⁸Si(³He, n)³⁰S; and ^58,60,62Ni(³He, n)^60,62,64Zn reactions have been measured at 25 MeV incident ³He energy using time-of-flight techniques. An overall energy resolution of about 1 percent for detection of 10-35 MeV neutrons provided accurate determinations of level excitations. Differential cross sections were extracted for many two particle states with up to 10 MeV excitation in the residual nuclei. By varying the beam incident angle and leaving the flight path somewhat …

The Eikonal Distorted Wave Born Approximation For The Excitation Of Hydrogen By Impact With Hydrogen And Helium In The Intermediate Energy Range, Richard Homer Shields

Doctoral Dissertations

"An eikonal approximation is applied to atom-atom scattering in the intermediate energy range. The theory and the form of the eikonal approximation are reviewed. Also a brief survey of previous theoretical methods for all energy ranges is included.

In particular, the differential and total cross sections for the excitation of hydrogen to the 2s and 2p states by impact on hydrogen and helium atoms have been calculated using the eikonal distorted wave Born approximation (DWBA) for the incident energy range of 2.25-100 keV. The eikonal DWBA differential cross sections are compared to the differential cross sections given by the first …

Ionization Mechanisms In Cesium, Yu Bong Hahn

Doctoral Dissertations

"Autoionizing states in Cs between 12 and 20 eV have been studied by electron impact. The retarding-potential-difference(RPD) method was used to obtain an electron beam with energy spread of about 0.1 eV. To determine the threshold energies, inelastically scattered electrons were analyzed by the trapped-electron method. We have been able to identify about 20 levels, and the agreement with spectroscopic data is excellent. A peak appearing at 12.80 eV is probably due to the quartet states observed by Feldman and Novick"--Abstract, page 2. "The structure in the electron impact ionization cross section in cesium can be partially accounted for by …

Time Resolved Measurements Of Droplet Growth In A Wilson Cloud Chamber, Michael Anthony Vietti

Doctoral Dissertations

"The growth rates of water drops in a Wilson expansion cloud chamber are measured with air, argon and helium as the carrier gas, in the size range of .5 to 10 microns. The drops growing in the supersaturated chamber exhibit oscillations in the scattered intensity as predicted by Mie theory. Scattered intensity is measured at 30 degrees to the He-Ne laser beam. Supersaturation ratios during growth range from S =1.2 to S = 3.5 for all three gases. The initial temperature is measured and the pressure is monitored continuously so that droplet growth theory can be compared with experiment. Three …

Radiative And Predissociative Lifetimes Of The A²Σ⁺ State Of Oh, Robert Allen Sutherland

Doctoral Dissertations

"Lifetime measurements have been made on the A²Σ⁺ state of OH by the delayed coincidence technique in conjunction with an interrupted rf discharge through water vapor. Lifetimes are reported for rotational states up to K = 29 and K = 20 in the v = 0 and v = 1 vibrational levels respectively and on the unresolved levels of v =2. A predissociation, previously predicted from relative intensity measurements, resulting from a curve crossing by the repulsive 4 Σˉ state, was observed for the rotational states above K = 23 of v = 0, for those above K = 14 …

Diffusiophoretic Forces Between Juxtaposed Atmospheric Particles, Allen L. Williams

Doctoral Dissertations

"The role of diffusiophoretics and Stefan flow in droplet growth by accretion and in-cloud scavenging is examined. A calculation is made for the diffusive forces between two juxtaposed spheres one or both of which are undergoing diffusional growth and the influence of the diffusive force on the trajectories of two spheres, assumed to obey the creeping flow equations is found. The results are: a) the diffusiophoretic force between two water droplets is zero. b) the diffusiophoretic force between a spherical ice particle and a water droplet, although non-zero, is too small to appreciably influence the fall trajectories. c) the diffusiophoretic …