Download or read book Structure and Dynamics of Small Molecules Studied by UV Laser Spectroscopy written by Gerardus Johannes Maria Meijer (molecilaire natuurkunde) and published by . This book was released on 1988 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure and Dynamics of Small Molecules Studied by UV Laser Spectroscopy written by Gerardus Johannes Maria Meijer and published by . This book was released on 1988 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure and Dynamics of Molecular Clusters Using Picosecond Laser Spectroscopy written by Maria Ivanna Shchuka and published by . This book was released on 1992 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structure of Small Molecules and Ions written by Ron Naaman and published by Springer. This book was released on 1988 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: The workshop on "The structure of small molecules and ions" was held at the Neve-Han guest house, near Jerusalem, Israel on December 13 to 18 in mem ory of the late Professor Itzhak Plesser. Professor Plesser played a central role in the research done both at the Weizmann Institute and at Argonne National Laboratories on the "Coulomb explosion" method. His friends honored his memory by organizing a meeting in which subjects related to Plesser's interests would be discussed. Just a week be fore the conference started we were struck by another tragedy -the death of our graduate student Ms. Hana Kovner, who participated in many of the Coulomb explosion experiments at the Weizmann Institute. We would like to dedicate these proceedings to her memory as well. The goal of the workshop was to bring together chemists and physicists working on different aspects of the structural problems of small molecular en tities. The time seemed appropriate for discussing experimental and theoretical concepts, since in recent years new methods have been introduced, and a large amount of information has been accumulated on systems not studied before, like unstable molecules, ions, van der Waals molecules and clusters. The program of the workshop reflects, we believe, these new developments. The meeting was characterized by intensive discussions in which the weak nesses and strengths of new and of well established concepts were revealed. We hope that it measured up to the high standards Itzhak Plesser maintained all through his scientific life.
Download or read book Interactions and Dynamics of Small Molecules in Liquid Mixtures written by Helena Kovács and published by . This book was released on 1990 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Solvation Structures and Dynamics of Small Molecules written by Xiaoliu Zhang and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Spectroscopy written by Wolfgang Demtröder and published by Springer Science & Business Media. This book was released on 2008-07-23 with total page 797 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keeping abreast of the latest techniques and applications, this new edition of the standard reference and graduate text on laser spectroscopy has been completely revised and expanded. While the general concept is unchanged, the new edition features a broad array of new material. This new edition has been completely revised, especially the chapters on non linear spectroscopy, ion trapping, ultra short laser pulses and new developments. Fifty new figures illustrate the newest developments and results. The author is one of the most renowned experts in this area and no other book with this broad scope is available.
Download or read book Ultrafast Molecular Dynamics Studied with Vacuum Ultraviolet Pulses written by Travis William Wright and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Studying the ultrafast dynamics of small molecules can serve as the first step in understanding the dynamics in larger chemically and biologically relevant molecules. To make direct comparisons with existing computational techniques, the photons used in pump-probe spectroscopy must make perturbative transitions between the electronic states of isolated small molecules. In this dissertation experimental investigations of ultrafast dynamics in electronic excitations of neutral ethylene and carbon dioxide are discussed. These experiments are performed using VUV/XUV femtosecond pulses as pump and probe. To make photons with sufficient energy for single photon transitions, VUV and XUV light is generated by high harmonic generation (HHG) using a high pulse energy ([approximately] 30 - 40 mJ) Ti:sapphire femtosecond laser. Sufficient flux must be generated to enable splitting of the HHG light into pump and probe arms. The system produces > 1010 photons per shot, corresponding to nearly 10 MW of peak power in the XUV. Using a high flux of high energy photons creates a unique set of challenges when designing a detector capable of performing pump-probe experiments. A velocity map imaging (VMI) detector has been designed to address these challenges, and has become a successful tool facilitating studies into molecular dynamics that were not possible before its implementation. The emphasis on using high energy, single photon transitions allowed theoretical calculations to be directly compared to experimental yields for the first time. This comparison resolved a long standing issue in the excited state lifetime of ethylene, and provided a confirmation of the branching ratio between the two nonadiabatic relaxation pathways that return ethylene back to its ground state from the [pi]*. The participation of the 3s Rydberg state has also been measured by collecting the time resolved photoelectron spectrum during the dynamics on ethylene [pi]* excited state, confirming calculations predicting the effect of the 3s. In carbon dioxide the first time resolved measurement in the lowest electronic excitation of carbon dioxide has been performed. A high kinetic energy release channel shows the signature of wavepacket dynamics within the excited state manifold. Deviation from the direct dissociation predicted for the pumped state provides experimental evidence confirming theoretical predictions of nonadiabatic transitions within the lowest lying electronically excited states.
Download or read book Studies of Solution Structure and Dynamics by Molecular Spectroscopy written by Michael Walter Balk and published by . This book was released on 1980 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure and Dynamics of Molecules and Molecular Aggregates in Gas Phase Studied by Femtosecond Spectroscopy written by Maksim Kunitski and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Spectroscopy 2 written by Wolfgang Demtröder and published by Springer. This book was released on 2015-01-07 with total page 773 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keeping abreast of the latest techniques and applications, this new edition of the standard reference and graduate text on laser spectroscopy has been completely revised and expanded. While the general concept is unchanged, the new edition features a broad array of new material, e.g., ultrafast lasers (atto- and femto-second lasers), coherent matter waves, Doppler-free Fourier spectroscopy, interference spectroscopy, quantum optics and gravitational waves and still more applications in chemical analysis, medical diagnostics, and engineering.
Download or read book Structures and Internal Dynamics of Cyclic Molecules Studied by Microwave Spectroscopy and Quantum Chemistry written by Vinh Van and published by . This book was released on 2017* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure and Dynamics in Small Biomolecular Systems written by Ivo Kalkman and published by . This book was released on 2009-07-01 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: The exact structure of large, biologically interesting molecules such as proteins is very important for the functions these molecules fulfill. To increase our understanding of the relationship between structure and function, and to enhance the predictive power of theoretical models, the structures of a few small model systems have been determined very precisely. Each of these model systems is closely related to important structural elements in proteins or DNA. The structure determination itself takes place by irradiating the molecules with UV laserlight and detecting which colors are absorbed by the molecule. It is found that especially the structures of systems with several chemically weak bonds differ substantially from theoretical predictions. Since the overall structure of nearly all large biomolecules is ultimately determined by these types of bonds the results presented in this thesis can be viewed as a small but important step towards a better understanding of biomolecular behavior in general.
Download or read book Molecules in Superfluid Helium Nanodroplets written by Alkwin Slenczka and published by Springer. This book was released on 2022-05-29 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book covers recent advances in experiments using the ultra-cold, very weakly perturbing superfluid environment provided by helium nanodroplets for high resolution spectroscopic, structural and dynamic studies of molecules and synthetic clusters. The recent infra-red, UV-Vis studies of radicals, molecules, clusters, ions and biomolecules, as well as laser dynamical and laser orientational studies, are reviewed. The Coulomb explosion studies of the uniquely quantum structures of small helium clusters, X-ray imaging of large droplets and electron diffraction of embedded molecules are also described. Particular emphasis is given to the synthesis and detection of new species by mass spectrometry and deposition electron microscopy.
Download or read book Structure and Dynamics of Supramolecular Systems One Molecule particle at a Time written by Pierre Karam and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past years, the possibility of visualizing single fluorescent molecules with exquisite spatial and temporal resolution has given rise to the field of Single Molecule Spectroscopy (SMS). The technique has enabled establishing new paradigms in biophysics and chemical biology by revealing unique information otherwise hidden in traditional ensemble measurements. In this work, we apply SMS methodologies to address problems in the field of chemistry and self-assembled structures, specifically to sense small molecules bound to a lipid membrane, to unravel exciton migration in conjugated polyelectrolytes, to study protein-RNA interactions and to characterize DNA nanotubes in solution. We discuss here the preparation and characterization of a liposome beacon platform for sensing small molecules. This platform relies on the interaction of conjugated polyelectrolytes with lipid membranes. The effect different lipids have on the photophysical properties of the ...
Download or read book Imaging Nuclear Motion During the Photofragmentation of Halomethane Molecules Triggered by Ultraviolet Light written by Farzaneh Ziaee and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the photoexcitation of molecules and visualizing the ensuing dynamics on their natural time scale is essential for our ability to describe and exploit many fundamental processes in different areas of science and technology. Prominent examples of such processes include, among many others, the adverse impacts of different classes of molecules on the ozone layer in atmospheric chemistry, light conversion into electricity through photovoltaics, photocatalysis, and some essential biological processes like vision and photosynthesis. Studies of molecular dynamics triggered by photon-molecule interaction underpin our understanding of many of these phenomena by adding the intermediate state to the "before-and-after" view of such photochemical or photobiological reactions. While identifying the initial molecular structure at equilibrium and determining the final products are crucial steps for the reaction characterization, understanding the dynamics connecting these initial and final states is essential for comprehending how the reaction really happens and potentially controlling its outcome. In other words, besides the "static" view of photo-induced reactions, identifying all intermediate states involved and mapping their spatio-temporal evolution are of great interest and importance. Since photoexcitation often induces coupled electron and nuclear motion on Angström spatial and femtosecond time scales, resolving such dynamics in space and time represents a significant scientific and technological challenge. Experimental tools to address this challenge have recently become available with the development of femtosecond lasers and imaging techniques capable of visualizing the evolving molecular structure. The present thesis aims to investigate the photodissociation dynamics of halomethane molecules triggered by ultraviolet (UV) light using coincidence ion momentum imaging as a primary structural characterization tool. Halomethanes are often considered as prototypical systems for molecular photodissociation in the UV domain. Due to the complicated excited-state structure driving the photochemistry of these molecules, they exhibit rich dynamics while being small enough to still allow for a detailed theoretical treatment. The primary goal of this work is to disentangle the photo-induced reaction channels, including direct and indirect dissociation pathways, and to visualize the motion of the individual molecular fragments in each of these channels. The photofragmentation reactions considered here include two- and three-body dissociation, transient isomerization and molecular halogen formation. The experiments are carried out at two different excitation wavelengths, 263 nm and 198 nm, which enables varying the dominant reaction pathways. To carry out these measurements, the 3rd and 4th harmonics of a 790 nm Ti: Sa femtosecond laser are used to initiate the dynamics of interest, which are then probed by multiple ionization and Coulomb explosion induced by an intense 790 nm pulse arriving after a variable time delay. The ions created in such pump-probe experiments are detected employing COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS). To facilitate interpreting the experimental results, they are compared to an extensive set of Coulomb explosion simulations. More specifically, this thesis describes three major studies. The first one is a set of time-resolved measurements on iodomethane (CH3I) photodissociation in the A-band, one of the best-studied reactions in ultrafast photochemistry. Here, the focus is on a detailed characterization of direct dissociation dynamics by Coulomb explosion imaging (CEI) and disentangling the competing reaction pathways involving single- and multi-photon excitations. The coincident measurement mode and an improved time resolution of 40-45 fs allowed us to observe a new feature in the two-body CEI pattern of this well-studied reaction, which was predicted theoretically but not yet observed experimentally, and to identify signatures of two- and three-photon processes populating Rydberg and ionic states. The second part of this work focuses on time-resolved studies of bromoiodomethane (CH2BrI) and chloroiodomethane (CH2ICl) photofragmentation in the A-band at 263 nm and, in particular, on imaging the co-fragment rotation. Here, the main objectives are to evaluate the effects of halogen-atom substitution on molecular dynamics and map the time evolution of individual photodissociation pathways. For these molecules, photoabsorption in the A-band predominantly breaks the C-I bond, with weaker but non-negligible contribution from the C-Br (or C-Cl) bond cleavage. Coincident two-body CEI analysis is used to map both of these channels, as well as a minor contribution from molecular halogen (IBr or ICl) formation. Three-body CEI patterns offer a deeper insight into the dynamics of these reactions and, in addition, reveal clear signatures of the three-body dissociation, which - at this wavelength - is most likely driven by the two-photon absorption. The three-body analysis also suggests that some fragmentation pathways pass through a transient linearized configuration, which is reached within ~100 fs from the initial photoabsorption and decays on a comparably fast time scale. One of the interesting aspects of dihalomethanes photodissociation in the A-band is that, unlike CH3I, where the excess energy is primarily channeled into translational motion, a significant portion of the available energy is partitioned into rotational excitation. Carbon-halogen bond cleavage results in the rotation of the molecular co-fragment, which can be unambiguously traced in the coincident three-body CEI maps for the corresponding dissociation channel. In this work, such rotational motion is directly imaged for the dissociation of either halogen atom, resulting in a "molecular movie" of the dissociating and rotating molecule. The third group of experiments described in this thesis includes time-resolved studies of bromoiodomethane and diiodomethane (CH2I2) photofragmentation in the B-band at 198 nm. In this part, the main goal is to trace the wavelength dependence of the photochemical reaction pathways. For CH2BrI, we observe a reversal of the branching ratio of C-I and C-Br bond cleavage compared to the 263 nm data, in agreement with earlier spectroscopic and theoretical studies. However, at 198 nm, three-body dissociation and molecular halogen formation become dominant photofragmentation channels for both molecules. Finally, the CH3I photodissociation is also studied in the B-band at 198 nm, where the excitation of the lowest-lying Rydberg states is expected to trigger pre-dissociation dynamics. Although no in-depth data analysis and modeling for this reaction have been carried out, the two-body CEI results clearly demonstrate the pre-dissociation nature of CH3I fragmentation at this wavelength, reflected in a broad, diffuse dissociation band, which is very different from distinct dissociation features observed for direct dissociation processes. Moreover, the data exhibit a pronounced oscillatory structure with a periodicity of 130-140 fs, which is visible only within the pre-dissociation lifetime of the excited state (~1.5 ps). While the exact origin of this structure remains unclear and will be a subject of further analysis and theoretical work, it most likely reflects the bound-state vibrational motion, which lasts until it pre-dissociates. The work presented in this thesis represents a significant step towards a better understanding of the UV-driven photochemistry of halomethanes and contains several examples of direct visualization of the atomic motion during these photochemical reactions. Our experimental approach enabled us to identify and disentangle different dissociation pathways and track their time evolution. The experimental methodology described here can be directly applied to investigate the light-driven nuclear motion in other molecular systems with different light sources.
Download or read book Research Awards Index written by and published by . This book was released on 1988 with total page 874 pages. Available in PDF, EPUB and Kindle. Book excerpt:
