Download or read book Investigation of Reactive Oxides and Radical Dynamics by Photoelectron Photofragment Coincidence Spectroscopy written by Katharine Lunny and published by . This book was released on 2019 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon, hydrogen, oxygen, and nitrogen are the most common elements necessary for life and in combination create a multitude of molecules. These include highly reactive species with complicated electronic structures, such as oxygenated hydrocarbon radicals and nitrogen oxides. These short-lived species can be important in atmospheric and combustion processes, but difficult to characterize due to their transient nature. Photoelectron-photofragment coincidence spectroscopy is a technique designed to study short-lived species thought photodetachment of the corresponding stable anion and measure the energy partitioning within the neutral species. The oxyallyl anion was photodetached to the nearly degenerate states, 3B2 and 1A1 as well the 3B1 excited state, which were correlated to predominately stable C3H4O neutral. The photoelectron spectrum of the oxyallyl diradical and the acetone enolate radical, C3H5O, are the correct assignment for the C2O2 and HC2O2 photoelectron spectra reported in the literature. The oxyallyl diradical was observed to have a minor dissociation channel, at both Ehv= 3.20 eV and 1.60 eV. At Ehv = 3.20 eV, photodetachment to the 1A1 state is accessible, and results in dissociation to CO + C2H4. Dissociation was also observed from the triplet states, occurring after intersystem crossing. This system is further complicated by the observation of photodetachment ~0.3 eV below threshold. A stable neutral was the result of delayed photoemission during cyclization, as well as dissociative photodetachment resulting from a two photon process were observed. The complicated electronic structure of nitrogen oxides, N2O2 and NO3 exhibit photodissociation pathways due the several neutral dissociation channels accessible at Ehv = 3.20 eV. For N2O2, photodissociation resulted in vibrationally excited NO anions which undergoes autodetachment, as well as photodissociation of NO− ([nu]=0). Photodissociation was also observed to result in N2O + O− which undergoes sequential photodetachment. The peroxynitrite anion, a high energy isomer of the nitrate anion, was also observed to produce similar photodissociation pathways. Vibrationally excited NO− followed by autodetachment was observed, as well as the observation of sequential photodetachment of O2− via a two-photon process.
Download or read book Probing Hydroxyl Radical Reactions Using Photoelectron Photofragment Coincidence Spectroscopy written by Yanice Benitez and published by . This book was released on 2020 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydroxyl radical plays a critical role in several contexts including combustion, atmospheric chemistry, and low-temperature extraterrestrial environments. OH has been observed in the interstellar medium and is important in the gas phase chemistry of interstellar clouds. Additionally, the hydroxyl radical is the dominant oxidizer of volatile organic compounds in the atmosphere. Here, the reactions between OH and simple alkanes, alkenes, and alcohols were investigated as these bimolecular reactions can expand fundamental understanding of gas phase reaction dynamics. Photoelectron-photofragment coincidence (PPC) spectroscopy was used to characterize the energetics and dynamics of the OH + CH4 --> H2O + CH3 reaction initiated by photodetachment of the OH-(CH4) anion complex. PPC measurements at a photon energy of 3.20 eV yielded stable and dissociative channels. Interpretation of the experimental results was supported by quantum chemistry and quasiclassical trajectory calculations showing that most of the trajectories yield slowly recoiling OH + CH4 reactants while some are trapped in the entrance channel van der Waals well. Extending the study to hydroxy radical reactions with the simplest alkene, ethylene, yielded similar dissociative photodetachment dynamics (DPD) to PPC studies on OH-(CH4). The dominant channel was DPD to OH + C2H4 + e- with a low kinetic energy release (KER) of the dissociating fragments, consistent with weak repulsion between the OH + C2H4 reactants near the transition state. To model the DPD process, an impulsive model was used to account for rotational energy partitioning in C2H4 photofragments and showed good agreement with the experimental results. PPC studies probing the OH + CH3OH --> H2O + CH3O reaction had the best Franck-Condon overlap with the exit channel. High-level coupled cluster calculations of the stationary points on the anion surface show that CH3O-(H2O) is the stable minimum. Photodetachment leads to H2O + CH3O + e- products with both direct dissociative photodetachment as well as resonance mediated processes observed on the neutral surface. The partitioning of total kinetic energy in the system indicates that water stretch and bend excitation is induced in DPD, and evidence for long-lived complexes consistent with production of vibrational Feshbach resonances in the exit channel is reported.
Download or read book Coincidence and Noncoincidence Studies of the Photodissociation Dynamics of Free Radicals written by Ann Elise Faulhaber and published by . This book was released on 2005 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photoisomerization and Photodissociation Dynamics of Reactive Free Radicals written by and published by . This book was released on 2000 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photofragmentation pathways of chemically reactive free radicals have been examined using the technique of fast beam photofragment translational spectroscopy. Measurements of the photodissociation cross-sections, product branching ratios, product state energy distributions, and angular distributions provide insight into the excited state potential energy surfaces and nonadiabatic processes involved in the dissociation mechanisms. Photodissociation spectroscopy and dynamics of the predissociative {tilde A}2A1 and {tilde B}2A2 states of CH3S have been investigated. At all photon energies, CH3 + S(3P{sub j}), was the main reaction channel. The translational energy distributions reveal resolved structure corresponding to vibrational excitation of the CH3 umbrella mode and the S(3P{sub j}) fine-structure distribution from which the nature of the coupled repulsive surfaces is inferred. Dissociation rates are deduced from the photofragment angular distributions, which depend intimately on the degree of vibrational excitation in the C-S stretch. Nitrogen combustion radicals, NCN, CNN and HNCN have also been studied. For all three radicals, the elimination of molecular nitrogen is the primary reaction channel. Excitation to linear excited triplet and singlet electronic states of the NCN radical generates resolved vibrational structure of the N2 photofragment. The relatively low fragment rotational excitation suggests dissociation via a symmetric C{sub 2V} transition state. Resolved vibrational structure of the N2 photofragment is also observed in the photodissociation of the HNCN radical. The fragment vibrational and rotational distributions broaden with increased excitation energy. Simple dissociation models suggest that the HNCN radical isomerizes to a cyclic intermediate (c-HCNN) which then dissociates via a tight cyclic transition state. In contrast to the radicals mentioned above, resolved vibrational structure was not observed for the ICNN radical due to extensive fragment rotational excitation, suggesting that intermediate bent states are strongly coupled along the dissociation pathway. The measurements performed in this Thesis have additionally refined the heats of formation and bond dissociation energies of these radicals and have unambiguously confirmed and added to the known electronic spectroscopy.
Download or read book Energetics and Dissociation Dynamics of Reactive Organic Intermediates written by Leah-Nani Soledad Alconcel and published by . This book was released on 2002 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2726 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Directory of Graduate Research written by and published by . This book was released on 2001 with total page 1846 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 774 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1989 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vibrational and Electronic Energy Levels of Polyatomic Transient Molecules written by Marilyn E. Jacox and published by Amer Inst of Physics. This book was released on 1994-01-01 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Faculties Publications and Doctoral Theses in Chemistry and Chemical Engineering at United States Universities written by American Chemical Society. Committee on Professional Training and published by . This book was released on 1991 with total page 1646 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cold Chemistry written by Olivier Dulieu and published by Royal Society of Chemistry. This book was released on 2017-12-06 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent years have seen tremendous progress in research on cold and controlled molecular collisions, both in theory and in experiment. The advent of techniques to prepare cold and ultracold molecules and ions, to store them in optical lattices or in charged quasicristalline structures, and to use them in crossed or merged beam experiments have opened many new possibilities to study the most fundamental aspects of molecular interactions. At the same time, theoretical work has made progress in tackling these problems and accurately describing quantum effects in complex systems, and in proposing viable options to control chemical reactions at ultralow energies. Through tutorials on both the theoretical and experimental aspects of research in cold and ultracold molecular collisions, this book provides advanced undergraduate students, graduate students and researchers with the foundations needed to understand this exciting field.
Download or read book Molecular Rays written by Ronald G. J. Fraser and published by Cambridge University Press. This book was released on 2015-12-03 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: Originally published in 1931, this book is concerned with the task of furthering the development of the physical method of molecular rays and was intended for the general reader. Written from an experimental standpoint, the book is a user-friendly survey, which could only be otherwise obtained by extensive reading of original papers. Chapters are broad in scope and range from 'The Diffraction of molecular rays' to 'Chemical equilibria, ionisation and spectroscopic applications'. Notably, chapter one, which deals with the technique of the production and measurement of the rays, has been written in more detail and serves as a laboratory manual for beginners in experimental work in molecular rays. Diagrams and plate sections are included for reference. This book includes almost every problem of surface chemistry and will be of great value to scholars in the field as well as to anyone with an interest in the history of physical chemistry.
Download or read book Multiconfigurational Quantum Chemistry written by Björn O. Roos and published by John Wiley & Sons. This book was released on 2016-08-08 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first book to aid in the understanding of multiconfigurational quantum chemistry, Multiconfigurational Quantum Chemistry demystifies a subject that has historically been considered difficult to learn. Accessible to any reader with a background in quantum mechanics and quantum chemistry, the book contains illustrative examples showing how these methods can be used in various areas of chemistry, such as chemical reactions in ground and excited states, transition metal and other heavy element systems. The authors detail the drawbacks and limitations of DFT and coupled-cluster based methods and offer alternative, wavefunction-based methods more suitable for smaller molecules.
Download or read book Chemistry for Sustainable Development written by Minu Gupta Bhowon and published by Springer. This book was released on 2014-02-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemistry for Sustainable Development is a collection of selected papers by the participants of the International Conference on Pure and Applied Chemistry (ICPAC 2010) on the theme of “Chemistry for Sustainable Development” held in Mauritius in July 2010. In light of the significant progresses and challenges in the development and implementation of green and sustainable chemistry, this volume reviews the recent results generated by a more efficient use of resources to minimize carbon footprints, to foster the eradication or minimisation of solvent use in chemistry, and to deliver processes which lead to increased harmony between chemistry and the environment. Chemistry for Sustainable Development is written for graduates, postgraduates, researchers in industry and academia who have an interest in the fields ranging from fundamental to applied chemistry.
Download or read book The Chemical Bond written by Ahmed Zewail and published by Elsevier. This book was released on 1992-05-14 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Physics Briefs written by and published by . This book was released on 1987 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt:
