Tracking Charge Migration with Attosecond X-ray Pulses from a Free-electron Laser PDF Download
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Author: Jordan Tyler O'Neal
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The motion of electrons in molecular superposition states happens on the attosecond timescale, roughly three orders of magnitude faster than nuclear motion. To study the first steps in a photochemical reaction, then, we must study the electron dynamics in early times before the nuclei have a chance to move. These purely electronic dynamics, uncoupled from nuclear motion, are dubbed charge migration (CM). CM can be described as a coherent superposition of delocalized electronic states evolving in time, which appears as a time-dependent oscillation in charge density across the molecule. On longer timescales, thought to be tens of femtoseconds, nuclear motion couples to the pure electronic CM. This tends to average out the CM, and there is evidence that this process can influence the nuclear reaction pathways. One can further envision using sequences of laser pulses to prepare CM states as a method of coherent control directing photochemical reaction pathways. However, understanding the loss of electronic coherence as nuclear motion occurs is difficult. Theoretical modeling of CM is computationally challenging, and there are open questions about the effects of nuclear motion. Experimental measurements can guide us towards better, more efficient approximations to help answer these outstanding questions. To this end, I present two experiments towards developing two separate methods for measuring CM. Both methods rely on the recently developed attosecond X-ray free-electron laser source at the LCLS free-electron laser facility. These two methods for measuring CM serve as early implementations of this new attosecond X-ray source. The first method to study CM, impulsive ionization, prepares a CM state by ionizing with an attosecond X-ray pulse which has coherent bandwidth large enough to populate multiple cationic states. The final state is then measured with X-ray absorption spectroscopy. I present preliminary results showing signatures of CM and nuclear motion damping the time-dependent charge density. The second method, nonlinear X-ray spectroscopy, is a sophisticated toolset using sequences of X-ray pulses to prepare and measure CM states. I present a measurement of a basic building block of nonlinear X-ray spectroscopy, impulsive stimulated X-ray Raman scattering, and use this result to show the feasibility in the near future of measuring valence CM states in a neutral molecule.
Author: Jordan Tyler O'Neal
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The motion of electrons in molecular superposition states happens on the attosecond timescale, roughly three orders of magnitude faster than nuclear motion. To study the first steps in a photochemical reaction, then, we must study the electron dynamics in early times before the nuclei have a chance to move. These purely electronic dynamics, uncoupled from nuclear motion, are dubbed charge migration (CM). CM can be described as a coherent superposition of delocalized electronic states evolving in time, which appears as a time-dependent oscillation in charge density across the molecule. On longer timescales, thought to be tens of femtoseconds, nuclear motion couples to the pure electronic CM. This tends to average out the CM, and there is evidence that this process can influence the nuclear reaction pathways. One can further envision using sequences of laser pulses to prepare CM states as a method of coherent control directing photochemical reaction pathways. However, understanding the loss of electronic coherence as nuclear motion occurs is difficult. Theoretical modeling of CM is computationally challenging, and there are open questions about the effects of nuclear motion. Experimental measurements can guide us towards better, more efficient approximations to help answer these outstanding questions. To this end, I present two experiments towards developing two separate methods for measuring CM. Both methods rely on the recently developed attosecond X-ray free-electron laser source at the LCLS free-electron laser facility. These two methods for measuring CM serve as early implementations of this new attosecond X-ray source. The first method to study CM, impulsive ionization, prepares a CM state by ionizing with an attosecond X-ray pulse which has coherent bandwidth large enough to populate multiple cationic states. The final state is then measured with X-ray absorption spectroscopy. I present preliminary results showing signatures of CM and nuclear motion damping the time-dependent charge density. The second method, nonlinear X-ray spectroscopy, is a sophisticated toolset using sequences of X-ray pulses to prepare and measure CM states. I present a measurement of a basic building block of nonlinear X-ray spectroscopy, impulsive stimulated X-ray Raman scattering, and use this result to show the feasibility in the near future of measuring valence CM states in a neutral molecule.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In the last few years laboratory-scale femtosecond laser-based research using XUV light has developed dramatically following the successful development of attosecond laser pulses by means of high-harmonic generation. Using attosecond laser pulses, studies of electron dynamics on the natural timescale that electronic processes occur in atoms, molecules and solids can be contemplated, providing unprecedented insight into the fundamental role that electrons play in photo-induced processes. In my talk I will briefly review the present status of the attosecond science research field in terms of present and foreseen capabilities, and discuss a few recent applications, including a first example of the use of attosecond laser pulses in molecular science. In addition, I will discuss very recent results of experiments where photoionization of dynamically aligned molecules is investigated using a high-harmonics XUV source. Photoionization of aligned molecules becomes all the more interesting if the experiment is performed using x-ray photons. Following the absorption of x-rays, ejected photoelectrons can be used as a probe of the (time-evolving) molecular structure, making use of intra-molecular electron diffraction. This amounts, as some have stated, to "illuminating the molecule from within". I will present the present status of our experiments on this topic making use of the FLASH free electron laser in Hamburg. Future progress in this research field not only depends on the availability of better and more powerful light sources, but also requires sophisticated detector strategies. In my talk I will explain how we are trying to meet some of the experimental challenges by using the Medipix family of detectors, which we have already used for time- and space-resolved imaging of electrons and ions.
Author: J. Hastings
Publisher: IOS Press
ISBN: 1643681338
Category : Science
Languages : en
Pages : 272
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Book Description
Many X-Ray Free-Electron Lasers (X-FELs) have been designed, built and commissioned since the first lasing of the Linac Coherent Light Source in the hard and soft X-ray regions, and great progress has been made in improving their performance and extending their capabilities. Meanwhile, experimental techniques to exploit the unique properties of X-FELs to explore atomic and molecular systems of interest to physics, chemistry, biology and the material sciences have also been developed. As a result, our knowledge of atomic and molecular science has been greatly extended. Nevertheless, there is still much to be accomplished, and the potential for discovery with X-FELs is still largely unexplored. The next generation of scientists will need to be well versed in both particle beams/FEL physics and X-ray photon science. This book presents material from the Enrico Fermi summer school: Physics of and Science with X-Ray Free-Electron Lasers, held at the Enrico Fermi International School of Physics in Varenna, Italy, from 26 June - 1 July 2017. The lectures presented at the school were aimed at introducing graduate students and young scientists to this fast growing and exciting scientific area, and subjects covered include basic accelerator and FEL physics, as well as an introduction to the main research topics in X-FEL-based biology, atomic molecular optical science, material sciences, high-energy density physics and chemistry. Bridging the gap between accelerator/FEL physicists and scientists from other disciplines, the book will be of interest to all those working in the field.
Author: E.L. Saldin
Publisher: Springer Science & Business Media
ISBN: 3662040662
Category : Technology & Engineering
Languages : en
Pages : 470
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Book Description
The Free Electron Laser (FEL) will be a crucial tool for research and industrial applications. This book describes the physical fundamentals of FELs on the basis of classical mechanics, electrodynamics, and the kinetic theory of charged particle beams, and will be suitable for graduate students and scientists alike. After a short introduction, the book discusses the theory of the FEL amplifier and oscillator, diffraction effects in the amplifier, and waveguide FEL.
Author: Volkhard May
Publisher: John Wiley & Sons
ISBN: 3527633812
Category : Science
Languages : en
Pages : 600
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Book Description
This 3rd edition has been expanded and updated to account for recent developments, while new illustrative examples as well as an enlarged reference list have also been added. It naturally retains the successful concept of its predecessors in presenting a unified perspective on molecular charge and energy transfer processes, thus bridging the regimes of coherent and dissipative dynamics, and establishing a connection between classic rate theories and modern treatments of ultrafast phenomena. Among the new topics are: - Time-dependent density functional theory - Heterogeneous electron transfer, e.g. between molecules and metal or semiconductor surfaces - Current flows through a single molecule. While serving as an introduction for graduate students and researchers, this is equally must-have reading for theoreticians and experimentalists, as well as an aid to interpreting experimental data and accessing the original literature.
Author: Dengming Xiao
Publisher: BoD – Books on Demand
ISBN: 1838803017
Category : Science
Languages : en
Pages : 140
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Book Description
Electrostatics and dielectric materials have important applications in modern society. As such, they require improved characteristics. More and more equipment needs to operate at high frequency, high voltage, high temperature, and other harsh conditions. This book presents an overview of modern applications of electrostatics and dielectrics as well as research progress in the field.
Author: Ahmed Zewail
Publisher: Elsevier
ISBN: 008092669X
Category : Science
Languages : en
Pages : 333
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Book Description
This inspired book by some of the most influential scientists of our time--including six Nobel laureates--chronicles our emerging understanding of the chemical bond through the last nine decades and into the future. From Pauling's early structural work using x-ray and electron diffraction to Zewail's femtosecond lasers that probe molecular dynamics in real time; from Crick's molecular biology to Rich's molecular recognition, this book explores a rich tradition of scientific heritage and accomplishment. The perspectives given by Pauling, Perutz, Rich, Crick, Porter, Polanyi, Herschbach, Zewail, and Bernstein celebrate major scientific achievements in chemistry and biology with the chemical bond playing a fundamental role. In a unique presentation that also provides some lively insights into the very nature of scientific thought and discovery, The Chemical Bond: Structure and Dynamics will be of general interest to scientists, science historians, and the scientifically inclined populous.
Author: Anatoly L. Buchachenko
Publisher: Springer Nature
ISBN: 9811525927
Category : Science
Languages : en
Pages : 195
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Book Description
In this book, Professor Anatoly Buchachenko gives a brief and informative description of the most striking achievements and discoveries made in the major natural sciences at the turn of the century – in the late twentieth and early twenty-first centuries. The author has a rare ability to describe scientific discoveries so that these achievements and their significance are understandable not only by professionals and scientists of all specialities, but for any reader interested in modern science, its role in the existence of mankind, and its impact on human society. Originally published in Russian, Professor Buchachenko’s book describes the interaction of natural sciences with social ones—philosophy and history—as well as the part played by the human factor in the development of science, especially the role of the great scientists.
Author: Kaoru Yamanouchi
Publisher: Springer
ISBN: 3319648403
Category : Science
Languages : en
Pages : 234
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Book Description
This thirteenth volume in the PUILS series covers a broad range of topics from this interdisciplinary research field, focusing on atoms, molecules, and clusters interacting in intense laser field and high-order harmonics generation and their applications. The series delivers up-to-date reviews of progress in ultrafast intense laser science, the interdisciplinary research field spanning atomic and molecular physics, molecular science, and optical science, which has been stimulated by the developments in ultrafast laser technologies. Each volume compiles peer-reviewed articles authored by researchers at the forefront of each their own subfields of UILS. Typically, each chapter opens with an overview of the topics to be discussed, so that researchers unfamiliar to the subfield, as well as graduate students, can grasp the importance and attractions of the research topic at hand; these are followed by reports of cutting-edge discoveries.
Author: Mohammad Azadeh
Publisher: Springer Science & Business Media
ISBN: 1441903046
Category : Science
Languages : en
Pages : 378
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Book Description
Within the past few decades, information technologies have been evolving at a tremendous rate, causing profound changes to our world and our ways of life. In particular, fiber optics has been playing an increasingly crucial role within the telecommunication revolution. Not only most long-distance links are fiber based, but optical fibers are increasingly approaching the individual end users, providing wide bandwidth links to support all kinds of data-intensive applications such as video, voice, and data services. As an engineering discipline, fiber optics is both fascinating and challenging. Fiber optics is an area that incorporates elements from a wide range of techno- gies including optics, microelectronics, quantum electronics, semiconductors, and networking. As a result of rapid changes in almost all of these areas, fiber optics is a fast evolving field. Therefore, the need for up-to-date texts that address this growing field from an interdisciplinary perspective persists. This book presents an overview of fiber optics from a practical, engineering perspective. Therefore, in addition to topics such as lasers, detectors, and optical fibers, several topics related to electronic circuits that generate, detect, and process the optical signals are covered. In other words, this book attempts to present fiber optics not so much in terms of a field of “optics” but more from the perspective of an engineering field within “optoelectronics.
