Femtosecond time resolved photoelectron spectroscopy in the extreme ultraviolet region PDF Download
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Author: Peter Šiffalovič
Publisher:
ISBN:
Category :
Languages : de
Pages : 104
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Book Description
Author: Peter Šiffalovič
Publisher:
ISBN:
Category :
Languages : de
Pages : 104
Get Book Here
Book Description
Author: Peter Šiffalovič
Publisher:
ISBN:
Category :
Languages : de
Pages : 104
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Author: Seyyed Javad Robatjazi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Photoelectron spectroscopy employing X-ray and extreme ultraviolet (XUV) radiation is one of the most important experimental methods to study the electronic structure of atoms, molecules, and solids. Recent developments of XUV and X-ray sources with ultrashort pulse durations, like free-electron lasers (FELs) and high-order harmonics of infrared lasers, enabled combining this approach with a concept of a time-resolved measurement, where a pair of synchronized short light pulses is used to initiate and observe a physical or chemical process of interest. Among other advances, such combination turned out to be particularly useful for atomic physics and gas-phase femtochemistry, where femtosecond or even sub-femtosecond short-wavelength radiation can be used to trigger the dynamics in high-lying states previously inaccessible for time-resolved measurements and offers a variety of novel schemes to probe light-induced electronic and nuclear motion. One of the key challenges for time-domain studies employing short-pulsed radiation sources is that they are necessarily broadband and, thus, typically populate a broad range of atomic of molecular states. The main goal of this thesis is to develop an experimental approach that enables state-selective analysis of the dynamics induced by such broadband femtosecond pulses in the XUV domain, and to apply it to study several exemplary reactions in photoionized molecules. Since reducing the bandwidth of the XUV pulse would ultimately limit the achievable temporal resolution, in this work the challenge of state selectivity is addressed by employing photoelectron-photoion and photoion-photoion coincident measurements. In the experimental apparatus developed as a part of this thesis, a double-sided velocity map imaging (VMI) spectrometer for coincident detection of electrons and ions is combined with a femtosecond pump-probe setup that includes a near-infrared (NIR) laser and a fiber-based XUV source based on high-order harmonics generation. This instrument has been commissioned, characterized, and applied to several time-resolved experiments on atomic and molecular targets. More specifically, this thesis describes three different sets of experiments. First, a brief overview of several XUV-NIR pump-probe measurements addressing two-color single, double or triple ionization of atoms is presented. Here, the main focus is set on capturing generic characteristic features of the corresponding two-color signals, and on revealing physical mechanisms determining their "transient" or "steady" behavior with respect to the time delay between the XUV and NIR pulses. The second series of experiments focuses on exploring coupled electronic and nuclear dynamics in XUV-ionized CO2 molecule probed by the synchronized NIR pulse. This study, which constitutes the central part of the thesis, relies on the detection of the photoelectron that reveals which electronic state is initially populated, in coincidence with ionic fragments, which provide information on the specific dissociation channel of the molecular ion after the interaction with both pulses. Here, we observe signatures of an electron-hole wave packet motion near a conical intersection of two low-lying cationic states, trace rotational dynamics determined by the dependence of the state-specific XUV photoionization cross section on molecular orientation, and disentangle the contributions of individual states to different dissociation pathways. The third series of experiments aims at studying nuclear dynamics in XUV-ionized alcohol molecules, focusing on the channels involving ultrafast hydrogen motion. Here, ion mass spectrometry measurements on methanol and its deuterated isotopologue CH3OH and CD3OH show that, depending on a specific XUV wavelength, the formation of molecular hydrogen or trihydrogen cations can be either dominated by the channels combining the hydrogen from the oxygen site with one or two hydrogens from the methyl carbon, or by the ejections of all hydrogen atoms from the methyl group. Coincident electron spectra for specific ionic fragments enable linking these channels to the calculated dissociation pathways leading to H2+ or H3+ formation. Finally, we present the results of XUV-NIR pump-probe experiments on ethanol, where a transient enhancement of particular dissociation channels has been observed. The experimental methodology presented in this work can be readily extended to a broad range of molecular systems, including both, molecular ions and high-lying excited states of the neutral molecules. At the same time, highly-differential data on small polyatomic molecules like CO2, methanol, and ethanol presented here, can be used to benchmark theoretical models for XUV ionization of these prototypical systems, improving our general understanding of light-induced molecular dynamics.
Author: Matthew Parkin Blackwell
Publisher:
ISBN:
Category :
Languages : en
Pages : 204
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Author: Anja Röder
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Alison Virginia Davis
Publisher:
ISBN:
Category :
Languages : en
Pages : 362
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Author: Cédric Schmidt
Publisher: Springer Nature
ISBN: 3030678385
Category : Science
Languages : en
Pages : 119
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Book Description
This work studies the relaxation dynamics of molecules in both the gas and liquid phases after strong field ionization, using transient absorption in the soft X-rays. In particular, the thesis presents the first realization of time-resolved X-ray absorption spectroscopy in the spectral water window with a laser-based HHG source. These remarkable experiments were not only performed for isolated molecules, but also in liquids, for which the spectral coverage of the K-edges of C, N, and O are of primary importance for investigating biological molecules. The technique relies on the generation of high-order harmonics to further probe the electronic structure of molecules. Using the atomic selectivity of high energies and the temporal coherence of laser technology, we demonstrate the observation of the first stages of chemical transformation of matter in the gas and liquid phases.
Author: Carolyn Patricia Schick
Publisher:
ISBN:
Category :
Languages : en
Pages : 300
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Author: Chi-Fong Lei
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Author: Thomas Weinacht
Publisher: CRC Press
ISBN: 0429804180
Category : Science
Languages : en
Pages : 358
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Book Description
This concise and carefully developed text offers a reader friendly guide to the basics of time-resolved spectroscopy with an emphasis on experimental implementation. The authors carefully explain and relate for the reader how measurements are connected to the core physical principles. They use the time-dependent wave packet as a building block for understanding quantum dynamics, progressively advancing to more complex topics. The topics are discussed in paired sections, one discussing the theory and the next presenting the related experimental methods. A wide range of readers including students and newcomers to the field will gain a clear and practical understanding of how to measure aspects of molecular dynamics such as wave packet motion, intramolecular vibrational relaxation, and electron-electron coupling, and how to describe such measurements mathematically.
