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Full-Text Articles in Physics

Diffractive Imaging Of Laser Induced Molecular Reactions With Kiloelectron-Volt Ultrafast Electron Diffraction, Yanwei Xiong Apr 2023

Diffractive Imaging Of Laser Induced Molecular Reactions With Kiloelectron-Volt Ultrafast Electron Diffraction, Yanwei Xiong

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Capturing the structural changes during a molecular reaction with ultrafast electron diffraction (UED) requires a high spatiotemporal resolution and sufficiently high signal-to-noise to record the signals with high fidelity. In this dissertation, I have focused on the development of a tabletop gas phase keV-UED setup with a femtosecond temporal resolution. A DC electron gun was employed to generate electron pulses with a high repetition rate of 5 kHz. The space charge effect in the electron pulse was ameliorated by compressing the 90 keV electron pulse longitudinally with a time varying electric field in an RF cavity. The velocity mismatch between …


Computational Studies Of Thermal Properties And Desalination Performance Of Low-Dimensional Materials, Yang Hong Aug 2019

Computational Studies Of Thermal Properties And Desalination Performance Of Low-Dimensional Materials, Yang Hong

Department of Chemistry: Dissertations, Theses, and Student Research

During the last 30 years, microelectronic devices have been continuously designed and developed with smaller size and yet more functionalities. Today, hundreds of millions of transistors and complementary metal-oxide-semiconductor cells can be designed and integrated on a single microchip through 3D packaging and chip stacking technology. A large amount of heat will be generated in a limited space during the operation of microchips. Moreover, there is a high possibility of hot spots due to non-uniform integrated circuit design patterns as some core parts of a microchip work harder than other memory parts. This issue becomes acute as stacked microchips get …


Gas-Phase Electron Diffraction From Laser-Aligned Molecules, Jie Yang, Martin Centurion Aug 2015

Gas-Phase Electron Diffraction From Laser-Aligned Molecules, Jie Yang, Martin Centurion

Martin Centurion Publications

Electron diffraction is a valuable tool to capture structural information from molecules in the gas phase. However, the information contained in the diffraction patterns is limited due to the random orientation of the molecules. Additional structural information can be retrieved if the molecules are aligned. Molecules can be impulsively aligned with femtosecond laser pulses, producing a transient alignment. The alignment persists only for a time on the order of a picosecond, so a pulsed electron gun is needed to record the diffraction patterns. In this manuscript, we describe the alignment process and show the changes in the diffraction pattern as …


Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility, Jun Dai, Xiao Cheng Zeng Jun 2015

Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility, Jun Dai, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A new two-dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct-gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in-plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10,000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. …


First-Principles Studies On Physical And Chemical Properties Of Nanostructures, Menghao Wu Dec 2011

First-Principles Studies On Physical And Chemical Properties Of Nanostructures, Menghao Wu

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

The physical and chemical properties of decorated graphene and graphene ribbons, single-layer III-V systems, three-dimensional carbon and BN foam, and transition-metal-molecular sandwich nanowires have been investigated by first-principle calculations and their potential applications have been predicted. First, it is shown that zigzag graphene nanoribbons (ZGNRs) can be converted into half metal when their edges are decorated by some chemical functional groups, and the half-metalicity is induced by chemical potential difference between two edges when one edge is decorated by electron-donating group like –OH and the other edge is decorated by electron-accepting group like –F, -NH2, -N(CH3) …


Ultrafast Rempi In Benzene And The Monohalobenzenes Without The Focal Volume Effect, Timothy D. Scarborough, James Strohaber, David B. Foote, Collin J. Mcacy, Cornelis J. Uiterwaal Jan 2011

Ultrafast Rempi In Benzene And The Monohalobenzenes Without The Focal Volume Effect, Timothy D. Scarborough, James Strohaber, David B. Foote, Collin J. Mcacy, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We report on the photoionization and photofragmentation of benzene (C6H6) and of the monohalobenzenes C6H5–X (X = F, Cl, Br, I) under intense-field, single-molecule conditions. We focus 50-fs, 804-nm pulses from a Ti:sapphire laser source, and record ion mass spectra as a function of intensity in the range ~1013 W/cm2 to ~1015 W/cm2. We count ions that were created in the central, most intense part of the focal area; ions from other regions are rejected. For all targets, stable parent ions (C6H5X+) are …