Atomic and Molecular Dynamics Probed by Intense Extreme Ultraviolet Attosecond Pulses
Atomic and Molecular Dynamics Probed by Intense Extreme Ultraviolet Attosecond Pulses

Author: Jasper Georg Christopher Peschel

Publisher:

Published: 2021

Total Pages:

ISBN-13: 9789180390156

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This thesis work was aimed to investigate dynamical processes in atoms and molecules on ultrafast time scales initiated by absorption of light in the extreme ultraviolet (XUV) regime. In particular, photoionization and photodissociation have been studied using pump-probe techniques involving ultrafast laser pulses. Such pulses are generated using either high-order harmonic generation (HHG) or free-electron lasers (FELs). The work of this thesis consists to a large extent in the development and application of a light source, enabling intense XUV attosecond pulses using HHG. In a long focusing geometry, a high-power infrared laser is frequency up-converted so as to generate a comb of high-order harmonics. An important aspect was the study of the spatial and temporal properties of the generated light pulses in order to gain control of their influence on the experiment. Combining theoretical and experimental results, the effect of the dipole phase on properties of high-order harmonics was explored, along with a metrological series of studies on the harmonic wavefront and the properties of the focusing optics used. Further, the HHG light source was employed to investigate photoionization. Individual angular momentum channels involved in the ionization were characterized using two-photon interferometry in combination with angle-resolved photoelectron detection. A method is applied allowing the full determination of channel-resolved amplitudes and phases of the matrix elements describing the single-photon ionization of neon. Finally, the process of photodissociation was investigated using light pulses generated via both HHG and FELs. The dissociation dynamics induced by multiple ionization of organic molecules were studied. Correlation techniques were used to unravel the underlying fragmentation dynamics, and additionally, pump-probe experiments provided insights into the time scales of the (pre-)dissociation dynamics.

Ultrafast Dynamics Driven by Intense Light Pulses
Ultrafast Dynamics Driven by Intense Light Pulses

Author: Markus Kitzler

Publisher: Springer

Published: 2015-07-24

Total Pages: 385

ISBN-13: 3319201735

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This book documents the recent vivid developments in the research field of ultrashort intense light pulses for probing and controlling ultrafast dynamics. The recent fascinating results in studying and controlling ultrafast dynamics in ever more complicated systems such as (bio-)molecules and structures of meso- to macroscopic sizes on ever shorter time-scales are presented. The book is written by some of the most eminent experimental and theoretical experts in the field. It covers the new groundbreaking research directions that were opened by the availability of new light sources such as fully controlled intense laser fields with durations down to a single oscillation cycle, short-wavelength laser-driven attosecond pulses and intense X-ray pulses from the upcoming free electron lasers. These light sources allowed the investigation of dynamics in atoms, molecules, clusters, on surfaces and very recently also in nanostructures and solids in new regimes of parameters which, in turn, led to the identification of completely new dynamics and methods for controlling it. Example topics covered by this book include the study of ultrafast processes in large molecules using attosecond pulses, control of ultrafast electron dynamics in solids with shaped femtosecond laser pulses, light-driven ultrafast plasmonic processes on surfaces and in nanostructures as well as research on atomic and molecular systems under intense X-ray radiation. This book is equally helpful for people who would like to step into this field (e.g. young researchers), for whom it provides a broad introduction, as well as for already experienced researchers who may enjoy the exhaustive discussion that covers the research on essentially all currently studied objects and with all available ultrafast pulse sources.

Attosecond and XUV Physics
Attosecond and XUV Physics

Author: Thomas Schultz

Publisher: John Wiley & Sons

Published: 2013-11-13

Total Pages: 624

ISBN-13: 3527677658

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This book provides fundamental knowledge in the fields of attosecond science and free electron lasers, based on the insight that the further development of both disciplines can greatly benefit from mutual exposure and interaction between the two communities. With respect to the interaction of high intensity lasers with matter, it covers ultrafast lasers, high-harmonic generation, attosecond pulse generation and characterization. Other chapters review strong-field physics, free electron lasers and experimental instrumentation. Written in an easy accessible style, the book is aimed at graduate and postgraduate students so as to support the scientific training of early stage researchers in this emerging field. Special emphasis is placed on the practical approach of building experiments, allowing young researchers to develop a wide range of scientific skills in order to accelerate the development of spectroscopic techniques and their implementation in scientific experiments. The editors are managers of a research network devoted to the education of young scientists, and this book idea is based on a summer school organized by the ATTOFEL network.

Attosecond Molecular Dynamics
Attosecond Molecular Dynamics

Author: Marc J J Vrakking

Publisher: Royal Society of Chemistry

Published: 2018-08-31

Total Pages: 512

ISBN-13: 1782629955

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Attosecond science is a new and rapidly developing research area in which molecular dynamics are studied at the timescale of a few attoseconds. Within the past decade, attosecond pump-probe spectroscopy has emerged as a powerful experimental technique that permits electron dynamics to be followed on their natural timescales. With the development of this technology, physical chemists have been able to observe and control molecular dynamics on attosecond timescales. From these observations it has been suggested that attosecond to few-femtosecond timescale charge migration may induce what has been called "post-Born-Oppenheimer dynamics", where the nuclei respond to rapidly time-dependent force fields resulting from transient localization of the electrons. These real-time observations have spurred exciting new advances in the theoretical work to both explain and predict these novel dynamics. This book presents an overview of current theoretical work relevant to attosecond science written by theoreticians who are presently at the forefront of its development. It is a valuable reference work for anyone working in the field of attosecond science as well as those studying the subject.

Attosecond Spectroscopic Studies of Atomic and Molecular Dynamics
Attosecond Spectroscopic Studies of Atomic and Molecular Dynamics

Author: Annelise Beck

Publisher:

Published: 2014

Total Pages: 104

ISBN-13:

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Isolated attosecond pulses with photon energies in the extreme ultraviolet have provided a new capability to study few-femtosecond and sub-femtosecond dynamics in atomic and molecular systems. A novel regime of attosecond transient absorption measurements, in which the near-infrared pulse follows the attosecond pulse, is reviewed. The observed timescales of the decay of an absorption feature and oscillations due to quantum beating are derived and experimental considerations for these measurements are discussed. Attosecond transient absorption spectroscopy is then applied to observe quantum beating between the 2s22p5(2P3/2)3d and 2s22p5(2P1/2)3d electronically excited states of neon. The quantum beating is observed more prominently in one of the absorption features, and theoretical models of the effect of the near-infrared pulse are proposed to explain this asymmetry and characterize the observed beating. In the model that most closely agrees with the measurement, the beating is detected via Rabi cycling induced by the near-infrared pulse through an intermediate state (likely one of the 3p states), and this mechanism is shown to be strongly dependent on the spectrum of the near-infrared pulse. The isolated attosecond pulses used in these experiments are characterized using the photoelectron streaking method and the duration of these pulses is measured by iteratively reconstructing the streaking spectrograms. The effect on the streaking spectrogram of various pulse characteristics, such as duration, chirp, and the presence of satellite pulses, is described. Streaking spectrograms using low photon energy attosecond pulses are typically asymmetric. The reasons for this asymmetry are discussed and the challenges of reconstructing these low energy pulses are addressed. Finally, attosecond pulses are used to investigate superexcited states, or doubly excited states above the ionization potential, of the nitrogen molecule (N2). These states can decay via two competing channels, autoionization and predissociation. Time-of-flight mass spectrometry is applied to measure lifetimes of these states. Preliminary results are presented and improvements to the experimental design are proposed.

Electron Dynamics in Solids Studied by Attosecond Extreme Ultraviolet Spectroscopy
Electron Dynamics in Solids Studied by Attosecond Extreme Ultraviolet Spectroscopy

Author: Lauren J. Borja

Publisher:

Published: 2016

Total Pages: 107

ISBN-13:

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The creation of attosecond pulses using high harmonic generation (HHG) to produce extreme ultraviolet light (XUV) pulses has enabled table-top core-level spectroscopy in both the gas and solid phase. Because HHG relies on a near infrared (NIR) driver pulse to create the XUV radiation, it is readily incorporated into pump-probe transient absorption and photoelectron spectroscopy experiments, giving way to measurements with unprecedented temporal resolution. The ability of attosecond XUV pump-probe spectroscopy to study solid state semiconductor materials allows for the interrogation of carriers on the timescales where a separation between electronic and lattice dynamics can occur. This will have far reaching implications addressing the fundamental carrier physics that govern the next generation of hot carrier charge transfer devices, which are at the forefront of photocatalytic and electronic device development. In this dissertation, a literature review of XUV transient absorption on solids using HHG is presented in Chapter 1. This chapter details the progress from femtosecond experiments on metal-oxide thin films to attosecond time-resolved experiments on semiconductors. In Chapter 2, the design and construction of the attosecond transient absorption apparatus capable of studying ultrafast dynamics in both solid state and gas phase samples using a near infrared (NIR) pump and an extreme ultraviolet (XUV) probe is presented. Chapter 3 presents transient absorption experiments done on germanium thin films, which measure both electrons and hole dynamics simultaneously in a single measurement. These results are supported by work from a theory collaboration. in Chapter 4, preliminary work on silicon germanium alloys is presented. While the results need further confirmation by additional experiments and characterization, it is clear that signals from hot carrier relaxation are present. Chapter 5 presents a theoretical investigation of a future experiment on silver nanoparticles using a velocity map imaging (VMI) device. The key feature of this theoretical study is the identification of a metric to follow the near-field of the plasmon, isolated from the electric field of the exciting laser pulse.

Femtosecond Molecular Dynamics Studied with Vacuum Ultraviolet Pulse Pairs
Femtosecond Molecular Dynamics Studied with Vacuum Ultraviolet Pulse Pairs

Author: Thomas K. Allison III

Publisher:

Published: 2010

Total Pages: 238

ISBN-13:

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Atoms and molecules have most of their oscillator strength in the vacuum ultraviolet (VUV) and extreme ultraviolet (XUV), between the wavelengths of 200 nm and 30 nm. However, most femtosecond spectroscopy has been restricted to the visible and infrared due to a lack of sufficiently intense VUV and XUV femtosecond light sources. This thesis discusses extensions of pump/probe spectroscopy to the VUV and XUV, and its application to the dynamics of ethylene and oxygen molecules excited at 161 nm. I begin with a detailed discussion of the short wavelength light source used in this work. The source is based on the high order harmonics of a near infrared laser and can deliver> 1010 photons per shot in femtosecond pulses, corresponding to nearly 10 MW peak power in the XUV. Measurements of the harmonic yields as a function of the generation conditions reveal the roles of phase matching and ionization gating in the high order harmonic generation process. Pump/probe measurements are conducted using a unique VUV interferometer, capable of combining two different harmonics at a focus with variable delay. Measurements of VUV multiphoton ionization allows for characterization of the source and the interferometer. In molecules, time resolved measurements of fragment ion yields reveal the femtosecond dynamics of the system. The range of wavelengths available for pump and probe allows the dynamics to be followed from photo-excitation all the way to dissociation without detection window effects. The dynamics in ethylene upon [pi] 2![pi]* excitation are protypical of larger molecules and have thus served as an important test case for advanced ab initio molecular dynamics theories. Femtosecond measurements to date, however, have been extremely lacking. In the present work, through a series of pump probe experiments using VUV and XUV pulses, time scales for the non-adiabatic relaxation of the electronic excitation, hydrogen migration across the double bond, and H2 molecule elimination are measured and compared to theory. In the simpler oxygen molecule, excitation in the Schuman-Runge continuum leads to direct dissociation along the B 3[Sigma]u- potential energy curve. The time resolved photoion spectra show that the total photoionization cross section of the molecule resembles two oxygen atoms within 50 fs after excitation.

Attosecond X-Ray Pulses for Molecular Electronic Dynamics
Attosecond X-Ray Pulses for Molecular Electronic Dynamics

Author: Mark Joseph Abel

Publisher:

Published: 2010

Total Pages: 214

ISBN-13:

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Attosecond pulses are opening a wide new field on the border of chemistry and physics. They offer the opportunity to initiate and probe electronic rearrangement of atoms, molecules, solids and clusters on the natural timescale of the electron motion. This thesis is about making and measuring attosecond pulses, with the ultimate goal of applying attosecond spectroscopy to molecules. In chapter 1, attosecond spectroscopy is reviewed in general. The applications of attosecond pulses to atoms and molecules, including successful experiments and theoretical predictions, are discussed. In chapter 2, techniques for making and measuring attosecond radiation are presented. This chapter focuses on high harmonic generation from tabletop laser sources, since synchrotron- and free-electron laser-based techniques are not yet experimentally demonstrated. Chapters 3 and 4 discuss in detail the laboratory setup for attosecond pulse generation, including the laser source, optical diagnostics, and attosecond delay line. The attosecond control of free electron motion with few-cycle laser pulses is presented in chapter 5. There, the carrier-envelope phase (CEP), and thus the attosecond temporal evolution of the laser field, leads to quantum interferences between free electron wavefunctions and lends control over the direction of electron emission. Attosecond pulse production is achieved in chapter 6 by gating harmonic generation on the leading edge of the driving laser pulse. The gate mechanism is shown to rely on the macroscopic ionization of the harmonic generation medium. This final chapter also demonstrates a new technique for assessing attosecond pulse temporal structure based on the inversion of the driving laser field in the laboratory frame of reference, called CEP-scanning.