Download or read book Femtosecond Electron Diffraction Studies of Strongly driven Structural Phase Transitions microform written by Bradley John Siwick and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2004 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: The new technique of femtosecond electron diffraction is developed and applied to the study of an ultrafast structural phase transition. A combination of numerical and analytical modeling is used to obtain a comprehensive understanding of the space-charge dominated propagation dynamics of high number density femtosecond electron pulses and to design a novel photoactivated electron gun. This electron source, capable of producing sub-500 femtosecond electron pulses with sufficient brightness to allow the study of even irreversible structural dynamics, is employed to investigate the strongly driven, laser-induced solid-to-liquid phase transition in polycrystalline aluminum. We are able to see, in real time, the loss of the long-range order present in the crystalline phase and the emergence of the liquid structure where only short-range atomic correlations are present; this transition occurs in 3.5 ps for thin-film aluminum with an excitation fluence of 70 mJ/cm2. The sensitivity and temporal resolution was sufficient to capture the time-dependent atomic pair correlation function as the material evolved from the solid to liquid state. These observations provide an atomic level description of the melting process in which the dynamics are best understood as a thermal phase transition under strongly driven conditions.

Download or read book Investigating Photoinduced Structural Changes in Silicon Using Femtosecond Electron Diffraction written by Maher Harb and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Physics of Structural Phase Transitions written by Minoru Fujimoto and published by Springer Science & Business Media. This book was released on 2005-12-06 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase transitions in which crystalline solids undergo structural changes present an interesting problem in the interplay between the crystal structure and the ordering process. This text, intended for readers with some prior knowledge of condensed-matter physics, emphasizes the basic physics behind such spontaneous structural changes in crystals. Starting with the relevant thermodynamic principles, the book discusses the nature of order variables and their collective motion in a crystal lattice; in a structural phase transition a singularity in such a collective mode is responsible for the lattice instability, as revealed by soft phonons. This mechanism is analogous to the interplay of a charge-density wave and a periodically deformed lattice in low-dimensional conductors. The text also describes experimental methods for modulated crystal structures and gives examples of structural changes in representative systems. The book is divided into two parts. The first, theoretical, part includes such topics as: the Landau theory of phase transitions; statistics, correlations and the mean-field approximation; pseudospins and their collective modes; soft lattice modes and pseudospin condensates; lattice imperfections and their role in the phase transitions of real crystals. The second part discusses experimental studies of modulated crystals using x-ray diffraction, neutron inelastic scattering, light scattering, dielectric measurements, and magnetic resonance spectroscopy.

Download or read book Development of an Ultrafast Low Energy Electron Diffraction Setup written by Max Gulde and published by Springer. This book was released on 2015-05-26 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an Ultrafast Low-Energy Electron Diffraction (ULEED) system that reveals ultrafast structural changes on the atomic scale. The achievable temporal resolution in the low-energy regime is improved by several orders of magnitude and has enabled the melting of a highly-sensitive, molecularly thin layer of a polymer crystal to be resolved for the first time. This new experimental approach permits time-resolved structural investigations of systems that were previously partially or totally inaccessible, including surfaces, interfaces and atomically thin films. It will be of fundamental importance for understanding the properties of nanomaterials so as to tailor their properties.

Download or read book Phase Transitions in Transition Metal Dichalcogenides Studied by Femtosecond Electron Diffraction written by Kerstin Haupt and published by . This book was released on 2013 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Femtosecond Electron Diffraction Using Relativistic Electron Pulses written by Jinfeng Yang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observation of atomic-scale structural motion in matter with femtosecond temporal resolution is of considerable interest to scientists and paves the way for new science and applications. For this purpose, ultrafast electron diffraction (UED) imaging using femtosecond electron pulses is a very promising technique, as electrons have a larger elastic scattering cross section as compared to photons or X-rays and can be easily focused in observation with high spatial resolution. In this chapter, we first give an overview of the historical development of current nonrelativistic UEDs and discuss the potentials of UEDs with relativistic electron pulses. Second, we describe the concept and development of relativistic UED with femtosecond electron pulses generated by a radio-frequency acceleration-based photoemission gun. Some demonstrations of diffraction imaging of crystalline materials using 3-MeV electron pulses with durations of ,ào100¬†fs are presented. Finally, we report a methodology of single-shot time-resolved diffraction imaging for the study of ultrafast dynamics of photo-induced irreversible phase transitions.

Download or read book Investigating Photoinduced Structural Changes in Si Using Femtosecond Electron Diffraction written by Maher Harb and published by . This book was released on 2009 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports on developing a femtosecond electron diffraction technique and its application in following the structural changes associated with photoexcited Si. Time resolved electron diffraction is capable in principle of capturing transient structures of photoinduced phenomena with femtosecond time resolution. In practice, however, the time resolution is severely limited by the broadening of electron pulses due to space-charge forces. Another technical difficulty lies in that diffraction in transmission geometry requires samples that are semi-transparent to electrons. These experimental challenges were dealt with using innovative engineering and software development, and novel nanofabrication methods. Subsequently, a robust highly automated experimental setup was established, and 50 nm free-standing membranes of polycrystalline Si were nanofabricated. These membranes were first excited below damage threshold with 387 nm light, at an absorbed fluence of 5.6 mJ/cm2. The observed loss of intensity and associated dynamics under these conditions are related to the Debye-Waller effect as the lattice heats up through electron-phonon processes. At high excitation levels, greater than ∼6% of the valence electron density, the crystalline structure of the lattice was lost in 500 fs. This observed time scale is indicative of an electronically driven order-to-disorder phase transition due to an abrupt change in the potential-energy landscape of the lattice. In addition, it was discovered that the high sensitivity of the electron diffraction process to shear-type deformation in single crystals makes the technique ideal to the generation and detection of coherent acoustic phonons. Longitudinal and shear acoustic phonons were subsequently resolved in (001)-oriented Si crystals. This study constitutes the first direct observation of shear phonons in symmetrically cut crystals, in sharp in contrast to the all-optical methods that rely on crystals asymmetrically cut at 20° to enhance the amplitude of the shear mode in order to detect its displacements.

Download or read book Chemistry in Action Making Molecular Movies with Ultrafast Electron Diffraction and Data Science written by Lai Chung Liu and published by Springer Nature. This book was released on 2020-09-10 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis provides the necessary experimental and analytical tools to unambiguously observe the atomically resolved chemical reactions. A great challenge of modern science has been to directly observe atomic motions during structural transitions, and while this was first achieved through a major advance in electron source brightness, the information content was still limited and new methods for image reconstruction using femtosecond electron diffraction methods were needed. One particular challenge lay in reconciling the innumerable possible nuclear configurations with the observation of chemical reaction mechanisms that reproducibly give the same kind of chemistry for large classes of molecules. The author shows that there is a simple solution that occurs during barrier crossing in which the highly anharmonic potential at that point in nuclear rearrangements couples high- and low-frequency vibrational modes to give highly localized nuclear motions, reducing hundreds of potential degrees of freedom to just a few key modes. Specific examples are given in this thesis, including two photoinduced phase transitions in an organic system, a ring closure reaction, and two direct observations of nuclear reorganization driven by spin transitions. The emerging field of structural dynamics promises to change the way we think about the physics of chemistry and this thesis provides tools to make it happen.

Download or read book Time resolved Electron Diffraction Studies of Phase Transitions at Low index Germanium Surfaces written by Xinglin Zeng and published by . This book was released on 2001 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Femtosecond Through Nanosecond Time Resolved Spectroscopy of Structural Phase Transitions written by Thomas P. Dougherty and published by . This book was released on 1991 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diffraction Studies of the Structural Phase Transition in the High Temperature Superconductor YBCO written by Bahram Khoshnevisan and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mapping Organic Molecular Motions with RF Compressed Femtosecond Electron Diffraction written by Meng Gao and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physics of Surfaces and Interfaces written by Harald Ibach and published by Springer Science & Business Media. This book was released on 2006-11-18 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: This graduate-level textbook covers the major developments in surface sciences of recent decades, from experimental tricks and basic techniques to the latest experimental methods and theoretical understanding. It is unique in its attempt to treat the physics of surfaces, thin films and interfaces, surface chemistry, thermodynamics, statistical physics and the physics of the solid/electrolyte interface in an integral manner, rather than in separate compartments. It is designed as a handbook for the researcher as well as a study-text for graduate students. Written explanations are supported by 350 graphs and illustrations.

Download or read book Fundamentals of Semiconductors written by Peter YU and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 651 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excellent bridge between general solid-state physics textbook and research articles packed with providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors "The most striking feature of the book is its modern outlook ... provides a wonderful foundation. The most wonderful feature is its efficient style of exposition ... an excellent book." Physics Today "Presents the theoretical derivations carefully and in detail and gives thorough discussions of the experimental results it presents. This makes it an excellent textbook both for learners and for more experienced researchers wishing to check facts. I have enjoyed reading it and strongly recommend it as a text for anyone working with semiconductors ... I know of no better text ... I am sure most semiconductor physicists will find this book useful and I recommend it to them." Contemporary Physics Offers much new material: an extensive appendix about the important and by now well-established, deep center known as the DX center, additional problems and the solutions to over fifty of the problems at the end of the various chapters.

Download or read book Physics Briefs written by and published by . This book was released on 1992 with total page 1332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Physics at the Limits written by Hartmut Figger and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 525 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published on the occasion of Theodor Hänsch's 60th Birthday emphasis is placed on precision related to results in a variety of fields, such as atomic clocks, frequency standards, and the measurement of physical constants in atomic physics. Furthermore, illustrations and engineering applications of the fundamentals of quantum mechanics are widely covered. It has contributions by Nobel prize winners Norman F. Ramsey, Steven Chu, and Carl E. Wieman.

Download or read book Advances in Solid State Physics 48 written by Rolf Haug and published by Springer Science & Business Media. This book was released on 2008-11-27 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 2008 Spring Meeting of the Arbeitskreis Festkörperphysik was held in Berlin, Germany, between February 24 and February 29, 2008 in conjunction with the 72nd Annual Meeting of the Deutsche Physikalische Gesellschaft. The 2008 meeting was the largest physics meeting in Europe and among the largest physics meetings in the world in 2008.