This collection contains selected research work by Theoretical and Applied Physics Students at the master's level, from 2009-2024. http://repository.aust.edu.ng/xmlui/handle/123456789/461 2026-04-09T10:09:29Z 2026-04-09T10:09:29Z Korir, Gideon Kiprono http://repository.aust.edu.ng/xmlui/handle/123456789/5148 2024-06-28T21:00:47Z 2023-11-02T00:00:00Z

Controlling XUV’s Harmonics Using Double IR Laser Pulses Korir, Gideon Kiprono Achieving efficient control of electrons and nuclei in atoms and molecules with lasers has been a subject of great interest for decades, in Physics and in Chemistry. One of the current and challenging questions with the today advanced in laser technology is how to generate and characterize a single and or a train of attosecond (1 𝑎𝑠 = 10−18 𝑠) laser pulses likely to control electrons in molecules. This therefore demands a proper mechanism that can lead to easy control of the extreme ultraviolet (XUV) harmonics.This is addressed in this work by first irradiating the Hydrogen atom H with a single infrared (IR) pulse and later with simultaneous interaction with double replica IR lasers of intensity 2 × 1014W/cm2 each. The order of frequency of emitted photons in the recombination process for two IR Lasers and for a single IR laser, interacting with the hydrogen atom without time delay, were 400 and 278, respectively. This High Harmonic Generation (HHG) of XUV’s depends on laser atom interaction which is governed by Time Dependent Schrödinger Equation (TDSE) and the Strong Field Approximations (SFA). By varying the time delay between the two simultaneous IR pulses, controlled harmonics are produced. It turns out that these delays caused spectral shifts which are smaller for longer time delays (the spectral shift for 400 a.u. time delay is smaller than that of 1250a.u. time delay). Main Thesis

2023-11-02T00:00:00Z Oladipo, Tolani Teslim http://repository.aust.edu.ng/xmlui/handle/123456789/5147 2024-05-30T21:00:42Z 2023-11-15T00:00:00Z

Decoherence and Nonclassicality of Quantum States Oladipo, Tolani Teslim The phase space representation of quantum mechanics is a well-known powerful tool for studying the correspondence between the density operator and classical distributions in phase space. This representation, known as the third formulation of quantum mechanics, is given in terms of the joint probability distribution (or more precisely the quasi-probability), and is independent of the conventional Hilbert space or the path integral formulations. In this representation one needs not choosing − coordinate or momentum − it works in the full phase space, accommodating the uncertainty principle, and offering a unique insight into the classical limit of quantum theory [1]. A variety of these representations exist, including Wigner [2], Husimi [3], P [4], Huwi [5], and are distinct from one another by the way they highlight classical structures against a background of quantum interferences. The study of decoherence is a long sought after goal in quantum optics. The question very often underpinning is how one can measure this decoherence or alternatively to what extent a system is quantum (with respect of course to the reference classical system, the coherent state). Recently an indicator of nonclassicality (quantumness) of a given system has been proposed [6] and has been successfully tested in a large number of quantum states of infinite dimensional Hilbert space. This indicator is based on the relative volume of the negative part of the Wigner function and is a quantitative measure of the degree to which a system is quantum. Attempts have been trying to link the negativity of the Wigner function with the entanglement of the analysed state on a composed Hilbert space [7]. The fundamentals of quantum mechanics in phase space were reviewed in this work, focusing mainly on the role of different distribution functions (quasi-distribution functions) with respect to the study of intriguing quantum phenomena. In particular, Wigner Distribution [2] and Non Classicality Indicator [6] were used to explore few quantum states [8], including the superposition of two Cat states, Squeezed Fork state and the Compass state [9] (a superposition of two pairs of Gaussians) for which the sub-Planck structures have been well demonstrated. Confidently, the resulting outputs will help to better understand and predict the quantumness of these quantum states as a function of their sizes or when they are exposed to perturbations. Main Thesis

2023-11-15T00:00:00Z Shehu, Mustapha http://repository.aust.edu.ng/xmlui/handle/123456789/5137 2023-12-18T22:01:50Z 2023-12-10T00:00:00Z

AB Initio Study of Surface Energy, Surface Stress and Coupling Coefficient of Au (111) Shehu, Mustapha This study investigates ab initio exploration of the Au (111) surface within the generalized gradient approximation, with a primary focus on assessing the convergence properties of this noble metal. An in-depth analysis of the material's response to various computational parameters, including cutoff energy, K-point sampling, and lattice parameter, was conducted to ensure the reliability and consistency of the findings. The theoretical determination of the lattice constant, yielding a value of 4.059 Å, not only aligns quantitatively with experimental measurements but also agrees with calculated values. A noteworthy aspect of this investigation involves reporting on the work function's response to strain, shedding light on how this essential property evolves under external influences. Additionally, the study evaluates the variation of energy per unit cell with varying slab thickness, providing insights into the material's behavior across different structural configurations. The results reveal that Au (111) exhibits a surface energy of 0.5561 𝑒𝑉Å−1, surface stress of 0.18177 𝑒𝑉Å−2and a coupling coefficient of 1.145 eV. These results provides significant implications for understanding the mechanisms associated with electrochemical coupling at an atomic scale, offering crucial insights into the material's behavior across diverse atomic and electronic structures. Thus this work contribute to the understanding of Au (111) surface properties, laying a foundation for advancements in understanding electrochemical phenomena and fostering the development of tailored applications in materials science and nanotechnology. Main Thesis

2023-12-10T00:00:00Z Ningang, Julius Mbuitoh http://repository.aust.edu.ng/xmlui/handle/123456789/5066 2022-08-26T21:00:42Z 2019-06-05T00:00:00Z

Modeling of the Origin and Interactions of Multisoliton Solutions of the (2+4)KdV Equation Ningang, Julius Mbuitoh Most of the relevant research work has addressed the properties of internal solitons in a greatly simplified environment, usually in the framework of different versions of the two layer fluid. The simplest equation of this class is the well-known Korteweg-de Vries (kdV) equation that describes the motion of weakly nonlinear internal waves in the long-wave limit. However, in many areas of the world’s ocean, the vertical stratification has a clearly pronounced three-layer structure, with well-defined seasonal thermocline at a depth of about 100m or higher. Hence , the need for a redefinition of the famous KdV equation to tackle such scenarios and clearly accounts for nonlinearity in such environments. In this work, we first derived an analytical solution for the (2+4) KdV-like equation which mimics such situations and numerically solved it using the pseudospectral methods due to its robustness. After numerical simulations, we observed that the multisoliton solution interactions, particularly the three soliton solution interaction showed similar properties with the two soliton solution interaction. 2019 Theoretical and Applied Physics Masters Theses

2019-06-05T00:00:00Z