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Nonresonant Multiphoton Ionization Of Alkaline Earth Atoms In Intense Laser Fields., Dal-Woo Kim
Nonresonant Multiphoton Ionization Of Alkaline Earth Atoms In Intense Laser Fields., Dal-Woo Kim
LSU Historical Dissertations and Theses
When an atomic beam interacts with a high intensity laser beam, ionization occurs even if the photon energy is less than the threshold level for ionization of the atom. In this thesis, nonresonant multiphoton ionization of alkaline-earth atoms is examined experimentally. Since alkaline-earth atoms have doubly excited states just above and sometimes below the first ionization threshold level and are easily ionized with relatively low intensity, they are ideally suited for studying the role of electron correlations in multiphoton ionization. This motivated a careful and detailed investigation of the correlation of electrons and the multiphoton ionization mechanism. A spectroscopic study …
Small Sample Calorimetry, And Specific Heat Of Gadolinium(1)Barium(2-X)Strontium(X)Copper(3)Oxygen(7)., Carter Harrison Watson
Small Sample Calorimetry, And Specific Heat Of Gadolinium(1)Barium(2-X)Strontium(X)Copper(3)Oxygen(7)., Carter Harrison Watson
LSU Historical Dissertations and Theses
The development of an automated small sample (0.5 to 50mg) calorimeter is discussed and evaluated. With this calorimeter, measurements of the specific heat of Gd$\sb1$Ba$\sb{\rm 2-x}$Sr$\sb{\rm x}$Cu$\sb3$O$\sb7$ for x = 0, 0.25, and 0.5 in the temperature range 0.6 to 3 K are reported. Measurements on the x = 0 sample agree with data collected by other groups. In addition, measurements in magnetic fields from 0 to 3 T for the x = 0 sample are reported. In each case a peak in the specific heat at the antiferromagnetic ordering temperature (the Neel temperature) is recorded and analyzed. Strontium doping …
Interacting Rydberg Channels In Diatomic Molecules., Ning Yi Du
Interacting Rydberg Channels In Diatomic Molecules., Ning Yi Du
LSU Historical Dissertations and Theses
A new model for a class of heteronuclear diatomic molecules is presented. This model readily combines multichannel quantum defect theory (MQDT) with a nonperturbative Fermi-type analysis. Applications to a series of alkali-He dimers, such as CsHe, have shown that this very simple model can give results (e.g. Born-Oppenheimer potential curves) very close to those from more elaborated methods (e.g. $\ell$-dependent pseudopotential method). Applications to heteronuclear rare gas dimers, such as ArXe, give the first detailed interpretation and classification of some of the observed spectra, which are too complicated to be studied by conventional molecular methods. Another MQDT application is also …
Using Tilted-Ring Models And Numerical Hydrodynamics To Study The Structure, Kinematics And Dynamics Of Hi Disks In Galaxies., Dimitris Michael Christodoulou
Using Tilted-Ring Models And Numerical Hydrodynamics To Study The Structure, Kinematics And Dynamics Of Hi Disks In Galaxies., Dimitris Michael Christodoulou
LSU Historical Dissertations and Theses
We model the structure, kinematics, and dynamics of neutral hydrogen gas in galaxies. Our attention is focused on specific features that are commonly observed mainly in the 21-cm line, such as twists, warps and polar rings. The intimate connection between these features and the presumed dark halos of galaxies is analyzed with the intention to discover ways to probe the dark matter of individual galaxies by simply observing the distribution and kinematics of the luminous matter. An important, intermediate step in this analysis is to demonstrate that the twists that appear in the isovelocity maps of many spiral galaxies (and …
Temporal Variations Of Cosmic Rays In The Heliosphere, Ping Ping Chih
Temporal Variations Of Cosmic Rays In The Heliosphere, Ping Ping Chih
Doctoral Dissertations
This thesis investigates temporal variations of cosmic rays in the heliosphere analytically. A perturbation approach is presented to solve the diffusion equation for energetic particle transport in the solar wind. A linear response of the cosmic ray number density to variations in the spatial diffusion coefficient is computed based on the convection-diffusion equation. As the simplest cases to study, the 11-year variation and a Forbush decrease, the assumptions are made (1) that the solar-cycle variation arises from an 11-year sinusoidal variation of the diffusion coefficient at the Sun which propagates out through the heliosphere and (2) a Forbush decrease arises …
High Resolution Inelastic Electron Scattering From Lead-208, James Patrick Connelly
High Resolution Inelastic Electron Scattering From Lead-208, James Patrick Connelly
Doctoral Dissertations
Inclusive electron scattering differential cross sections from $\sp{208}$Pb have been measured with energy resolutions better than 20 keV for over 120 discrete states with excitation energies less than 7.3 MeV. The momentum-transfer dependence of these cross sections has been mapped over a range of 0.5 to 2.8 $fm\sp{-1}$ in the forward direction and 1.0 to 2.9 $fm\sp{-1}$ in the backward scattering direction. Over fifty excitations have been analyzed in the Distorted Wave Born Approximation to yield transition charge, current and magnetization densities. The nuclear structure of discrete excitations are interpreted in the framework of 1p-1h transition. The nuclear structure of …
Ground-Level Atmospheric Gamma-Ray Flux Measurements In The 1-6 Mev Range, Parameswaran Sreekumar
Ground-Level Atmospheric Gamma-Ray Flux Measurements In The 1-6 Mev Range, Parameswaran Sreekumar
Doctoral Dissertations
This thesis deals with the measurement of atmospheric gamma ray flux in the 1-6 MeV range at ground level. These measurements were carried out using a Compton gamma ray telescope, developed at the University of New Hampshire. It utilizes the Compton scattering principle to detect and image gamma ray sources. The telescope was used to measure ground level atmospheric gamma rays at four locations (Leadville (10200 ft), Boulder (5430 ft), Mt. Washington (6072 ft) and Durham (80 ft)) which ranged in atmospheric depth from 720-1033 g/cm$\sp2$ and in local cutoff rigidity from 1.4-2.9 GV. Data was collected over a two …
Far-Infrared Studies Of Vibrational Spectra Of The Rare Earth Doped Fluorite Crystals., Juergen. Demsky
Far-Infrared Studies Of Vibrational Spectra Of The Rare Earth Doped Fluorite Crystals., Juergen. Demsky
Electronic Theses and Dissertations
A zero-phonon assisted 4f-5d electronic transition of a trivalent rare earth in a fluorite host is accompanied by a vibronic sideband. This sideband resembles the single phonon density of states of the crystalline host with notable exceptions. A strong feature above the $\omega$$\sb{\rm LO}$(k = O) frequency of the host lattice is present, and is attributed to a local phonon mode feature of the defect crystal. The frequency of this local mode is weakly dependent on the trivalent rare earth and depends on the fluorite host chosen. The presence of this mode in the ultraviolet absorption spectrum of a XF$\sb{\rm …
Evaluation Of Two-Body Operator Matrix Elements In The Unitary Group Approach With Applications To Nuclear Magnetic Resonance., Pardu S. Ponnapalli
Evaluation Of Two-Body Operator Matrix Elements In The Unitary Group Approach With Applications To Nuclear Magnetic Resonance., Pardu S. Ponnapalli
Electronic Theses and Dissertations
The unitary group approach to angular momentum theory is applied to evaluate matrix elements of the nuclear spin-spin coupling Hamiltonian. The important case of two spin $-{1\over 2}$ particles in an external field which is a prototypical case for many NMR studies is analyzed in the framework of the unitary group approach. To aid in the evaluation of matrix elements of the nuclear spin-spin coupling Hamiltonian for higher spin nuclei, we introduce simple factorization schemes for evaluating two body operator matrix elements in the Unitary Group Approach. The results are applied to an $A\sb4 B\sb3$ system and compared with previous …
Muon Pair Production At 52 Gev Less Than-Equal To Sqrt.S. Less Than-Equal To 57 Gev Using The Amy Detector At Tristan., Angelina M. Bacala
Muon Pair Production At 52 Gev Less Than-Equal To Sqrt.S. Less Than-Equal To 57 Gev Using The Amy Detector At Tristan., Angelina M. Bacala
LSU Historical Dissertations and Theses
The reaction e$\sp+$e$\sp-$ $\to$ $\mu\sp+\mu\sp-$ has been observed by the AMY Detector at 52 GeV $\leq$ $\sqrt{s}$ $\leq$ 57 GeV at the TRISTAN storage ring in Tsukuba, Japan. With an integrated luminosity of 18.6 pb$\sp{-1}$, this presents a new test of the standard model of the electroweak interactions in this previously unexplored energy region. The forward-backward charge asymmetry and the cross-section calculated at the various energies show agreement with the standard model predictions. The products of the vector and the axial-vector coupling constants of the electron and muon extracted from these measurements are also consistent with theory. The data were …
Polarized Radiation From Inhomogeneous Shocks., Kinwah Wu
Polarized Radiation From Inhomogeneous Shocks., Kinwah Wu
LSU Historical Dissertations and Theses
Strongly polarized radiation from AM Herculis binaries is believed to be due to cyclotron emission from hot magnetized plasmas. The flat optically thin spectra and strong IR polarization observed in these binaries cannot be explained by models assuming a homogeneous emission region with a simple geometry. We have therefore studied the cyclotron emission from infinite plasma cylinders with uniform magnetic fields and temperatures, but with a variety of axially symmetric electron density profiles and shown that such inhomogeneous plasmas are able to produce relatively flat spectra which cannot be produced by the homogeneous models. The polarization at low frequencies is …
The Study Of Model Hamiltonians On Finite Clusters., Duan Pin Chen
The Study Of Model Hamiltonians On Finite Clusters., Duan Pin Chen
LSU Historical Dissertations and Theses
We present two methods to study model Hamiltonians defined on clusters. One is the symmetrization of the Hilbert space basis according to irreducible representations of the symmetry group of the Hamiltonian. The other one adapts the Lanczos diagonalization method directly to the second quantized form of the Hamiltonian studied. By the symmetrization of the basis, one takes advantage of the symmetries of the Hamiltonian, and uses the group theory to find the invariant subspaces of the Hamiltonian in the complete Hilbert space. Then one needs only to work within the invariant subspaces. This method cuts down substantially the size of …
Precision Measurement Of The 1s2s(1)S(0)-1s2p(1)P(1) Interval In Heliumlike Beryllium, Timothy James Scholl
Precision Measurement Of The 1s2s(1)S(0)-1s2p(1)P(1) Interval In Heliumlike Beryllium, Timothy James Scholl
Digitized Theses
This work represents the first test of non-relativistic, relativistic, and quantum electrodynamic calculations for two-electron systems using a high precision measurement of the 2{dollar}\sp1{dollar}S-2{dollar}\sp1{dollar}P interval of a heliumlike ion. The method of laser resonance spectroscopy on a fast ion beam of ions was used to measure the 1s2s{dollar}\sp1{dollar}S{dollar}\sb0{dollar}-1s2p{dollar}\sp1{dollar}P{dollar}\sb1{dollar} interval of heliumlike beryllium to be 16276.774(9) cm{dollar}\sp{lcub}-1{rcub}{dollar}. Absolute frequency calibration was provided by the iodine atlas of Gerstenkorn and Luc. This result is in excellent agreement with both theory and previous experiment with an improvement in experimental precision by a factor of 11.;The measurement of the width of the observed laser …
Laser Spectroscopy Of The Mercury-Zinc Excimer., Ezzat M. Hegazi
Laser Spectroscopy Of The Mercury-Zinc Excimer., Ezzat M. Hegazi
Electronic Theses and Dissertations
Extensive and previously unknown fluorescence and excitation spectra of the HgZn excimer have been observed and correlated with a potential energy (PE) diagram drawn and labelled according to Hund's case (c). The spectra were excited in a Hg-Zn mixture contained in a quartz vapour cell by successive pulses from two dye lasers using the pump-and-probe method, and were recorded using techniques of time-resolved fluorescence spectroscopy. The reservoir states, which became populated by the pump pulse, were found to be the A1, AO$\sp-$ and AO$\sp+$ states. The fluorescence band at 4750 A, which has a 6$\mu$s lifetime and was first observed …
A Jet Calculus Approach Including Coherence Effects And The Associated Problem Of Moment Inversion, Kumbakonam S. Sowmyanarayanan
A Jet Calculus Approach Including Coherence Effects And The Associated Problem Of Moment Inversion, Kumbakonam S. Sowmyanarayanan
Digitized Theses
We study the production of colourless clusters (CC) in high energy {dollar}e\sp{lcub}+{rcub}e\sp{lcub}-{rcub}{dollar} collisions in the framework of perturbative QCD. We adopt a jet calculus approach, which enables us to treat the cascade of successively generated partons initiated by the virtual photon in the above process in terms of quantum mechanical probabilities rather than amplitudes. Special attention is given to the presence of soft gluons in the cascade, which produce non-negligible quantum mechanical interference contributions thus causing a serious obstacle to the probabilistic view inherent in jet calculus and its subsequent refinements; among these the Crespi-Jones (CJ) approach is ideally suited …
Operator Regularization And Renormalization Theory, Louis Borna Culumovic
Operator Regularization And Renormalization Theory, Louis Borna Culumovic
Digitized Theses
In the past few years a new method of regularization, called operator regularization (o.r.), has been developed to regulate formal divergences that arise in quantum field theory. This technique is characterized by the fact that no divergent quantities ever arise once the technique is applied, even after the regulating parameter approaches its limiting value, and that under certain conditions the symmetries present in the initial Lagrangian are not explicitly broken. The technique is developed in more detail for beyond one-loop order in perturbation theory, and some two-loop calculations in o.r. are done for the first time. First, the Schwinger expansion, …