Degree Discipline

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Angular Dependence of the Stopping Processes and the Yields of Ion-induced Electron Emission from Channeled MEV Protons in <100> Silicon Foils (open access)

Angular Dependence of the Stopping Processes and the Yields of Ion-induced Electron Emission from Channeled MEV Protons in <100> Silicon Foils

The present work reports the experimental evidence of anomalous energy loss, energy straggling, and the corresponding ion-induced electron emission yields of channeled protons in silicon.
Date: December 1993
Creator: Zhao, Zhiyong
System: The UNT Digital Library
Linear, Nonlinear Optical and Transport Properties of Quantum Wells Composed of Short Period Strained InAs/GaAs Superlattices (open access)

Linear, Nonlinear Optical and Transport Properties of Quantum Wells Composed of Short Period Strained InAs/GaAs Superlattices

In this work, ordered all-binary short-period strained InAs/GaAs superlattice quantum wells were studied as an alternative to strained ternary alloy InGaAs/GaAs quantum wells. InGaAs quantum wells QWs have been of great interest in recent years due to the great potential applications of these materials in future generations of electronic and optoelectronic devices. The all binary structures are expected to have all the advantages of their ternary counterparts, plus several additional benefits related to growth, to the elimination of alloy disorder scattering and to the presence of a higher average indium content.
Date: December 1993
Creator: Huang, Xuren
System: The UNT Digital Library
Deterministic Brownian Motion (open access)

Deterministic Brownian Motion

The goal of this thesis is to contribute to the ambitious program of the foundation of developing statistical physics using chaos. We build a deterministic model of Brownian motion and provide a microscpoic derivation of the Fokker-Planck equation. Since the Brownian motion of a particle is the result of the competing processes of diffusion and dissipation, we create a model where both diffusion and dissipation originate from the same deterministic mechanism - the deterministic interaction of that particle with its environment. We show that standard diffusion which is the basis of the Fokker-Planck equation rests on the Central Limit Theorem, and, consequently, on the possibility of deriving it from a deterministic process with a quickly decaying correlation function. The sensitive dependence on initial conditions, one of the defining properties of chaos insures this rapid decay. We carefully address the problem of deriving dissipation from the interaction of a particle with a fully deterministic nonlinear bath, that we term the booster. We show that the solution of this problem essentially rests on the linear response of a booster to an external perturbation. This raises a long-standing problem concerned with Kubo's Linear Response Theory and the strong criticism against it by van …
Date: August 1993
Creator: Trefán, György
System: The UNT Digital Library
Numerical Investigations of Quantum Effects of Chaos (open access)

Numerical Investigations of Quantum Effects of Chaos

The quantum dynamics of minimum uncertainty wave packets in a system described by the surface-state-electron (SSE) Hamiltonian are studied herein.
Date: August 1993
Creator: Miroslaw, Latka
System: The UNT Digital Library
An Experimental Study of Collision Broadening of some Excited Rotational States of the Bending Vibration of Methyl Cyanide (open access)

An Experimental Study of Collision Broadening of some Excited Rotational States of the Bending Vibration of Methyl Cyanide

A double modulation microwave spectrometer is used to evaluate the linewidth parameters for some excited rotational components in the bending vibration v_8 of 13CH3 13C 15N and 13CH3C15N isotopomers of methyl cyanide. The linewidth parameters for self-broadening of the ΔJ=2←1 rotational components for the ground v_8 , 1v_8, and the 2v_8 vibrations were determined over a pressure range of 1 to 13 mtorr and at a temperature of 300 K. The double modulation technique is used to explore the high eighth derivative of the line shape profile of the spectral line. This technique proved to give good signal-to-noise ratios and enabled the recovery of weak signals. An experimental method is developed to correct for source modulation broadening. The tests of the ratios of the two inner peak's separation of the eighth derivative of the line showed that they were up to 95% similar to those for a Lorentzian line shape function. The line shapes were assumed to be Lorentzian for the theoretical analysis of the derivative profiles and comparisons were made between experiment and theory on this basis. Dipole moments for vibrationally excited states were calculated from linewidth parameters and show systematic decrease with the increase of excitation. Impact parameters …
Date: May 1993
Creator: Hajsaleh, Jamal Y. (Jamal Yousef)
System: The UNT Digital Library
Z1 Dependence of Ion-Induced Electron Emission (open access)

Z1 Dependence of Ion-Induced Electron Emission

Knowledge of the atomic number (Zt) dependence of ion-induced electron emission yields (Y) can be the basis for a general understanding of ion-atom interaction phenomena and, in particular, for the design of Zrsensitive detectors that could be useful, for example, in the separation of isobars in accelerator mass spectrometry. The Zx dependence of ion-induced electron emission yields has been investigated using heavy ions of identical velocity (v = 2 v0, with v0 as the Bohr velocity) incident in a normal direction on sputter-cleaned carbon foils. Yields measured in this work plotted as a function of the ion's atomic number reveal an oscillatory behavior with pronounced maxima and minima. This nonmonotonic dependence of the yield on Zx will be discussed in the light of existing theories.
Date: December 1993
Creator: Arrale, Abdikarim M. (Abdikarim Mohamed)
System: The UNT Digital Library
Synchronous Chaos, Chaotic Walks, and Characterization of Chaotic States by Lyapunov Spectra (open access)

Synchronous Chaos, Chaotic Walks, and Characterization of Chaotic States by Lyapunov Spectra

Four aspects of the dynamics of continuous-time dynamical systems are studied in this work. The relationship between the Lyapunov exponents of the original system and the Lyapunov exponents of induced Poincare maps is examined. The behavior of these Poincare maps as discriminators of chaos from noise is explored, and the possible Poissonian statistics generated at rarely visited surfaces are studied.
Date: August 1993
Creator: Albert, Gerald (Gerald Lachian)
System: The UNT Digital Library