Molecular Beams Studies of the Energetics and Dynamics of Elementary Chemical Reactions PDF Download

Author: Carl Clay Hayden
Publisher:
ISBN:
Category : Molecular beams
Languages : en
Pages : 146

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Author:
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Category :
Languages : en
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Quantum mechanical effects on the angular distribution of HF products from the F + H2 reaction were studied using crossed atomic and molecular beams with a rotatable mass spectrometer detector and time-of-flight velocity analysis. Measurement of the singlet-triplet splitting of CH2 from the recoil velocities of fragments from ketene photodissociation in a molecular beam is also reported. Partial center-of-mass angular distributions, and velocity flux contour maps have been derived for individual vibrational states of the HF product from the F + H2 reaction at collision energies of 2 and 3 kcal/mole. The center-of-mass distributions were obtained by analysis of laboratory angular and time-of-flight measurements of the reactive scattering. The results are consistent with recent three dimensional quantum mechanical scattering calculations, which predict that resonance effects should appear in the product angular distributions in this energy range. The photofragmentation of ketene in a molecular beam was used to measure the singlet-triplet splitting in CH2. A rare gas halide excimer laser operating at 351 nm (XeF) and 308 nm (XeCl) dissociated the ketene. Time-of-flight measurements of the fragment velocities allowed determination of the energetics of the dissociation. The 1A1 - 3B1 splitting in CH2 was found to be 8.5 +- 0.8 kcal/mole. This agrees with many experimental results, but not with the value of 19.5 kcal/mole derived from recent photodetachment experiments on CH2−.

Author:
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ISBN:
Category :
Languages : en
Pages : 7

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Thrust was to elucidate simple elementary reactions and to unravel mechanism of complex/photochemical reactions. Molecular beams are used to study reactions between molecules or to monitor photodissociation events in a collision-free environment. Recent activities centered on reactions involving oxygen atoms with unsaturated hydrocarbons, endothermic substitution reactions, dependence of reactivity of excited atoms on alignment of excited orbitals, photochemical reactions of polyatomic, energy transfer, free radicals in combustion processes, infrared absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation.

Author: Ian W. M. Smith
Publisher: Butterworth-Heinemann
ISBN: 1483161994
Category : Science
Languages : en
Pages : 400

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Kinetics and Dynamics of Elementary Gas Reactions surveys the state of modern knowledge on elementary gas reactions to understand natural phenomena in terms of molecular behavior. Part 1 of this book describes the theoretical and conceptual background of elementary gas-phase reactions, emphasizing the assumptions and limitations of each theoretical approach, as well as its strengths. In Part 2, selected experimental results are considered to demonstrate the scope of present day techniques and illustrate the application of the theoretical ideas introduced in Part 1. This publication is intended primarily for working kineticists and chemists, but is also beneficial to graduate students.

Author: W. Miller
Publisher: Springer Science & Business Media
ISBN: 1475706448
Category : Science
Languages : en
Pages : 391

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Activity in any theoretical area is usually stimulated by new experimental techniques and the resulting opportunity of measuring phenomena that were previously inaccessible. Such has been the case in the area under consideration he re beginning about fifteen years aga when the possibility of studying chemical reactions in crossed molecular beams captured the imagination of physical chemists, for one could imagine investigating chemical kinetics at the same level of molecular detail that had previously been possible only in spectroscopic investigations of molecular stucture. This created an interest among chemists in scattering theory, the molecular level description of a bimolecular collision process. Many other new and also powerful experimental techniques have evolved to supplement the molecular be am method, and the resulting wealth of new information about chemical dynamics has generated the present intense activity in molecular collision theory. During the early years when chemists were first becoming acquainted with scattering theory, it was mainly a matter of reading the physics literature because scattering experiments have long been the staple of that field. It was natural to apply the approximations and models that had been developed for nuclear and elementary particle physics, and although some of them were useful in describing molecular collision phenomena, many were not.

Author: I. Smith
Publisher: Springer Science & Business Media
ISBN: 1468435574
Category : Science
Languages : en
Pages : 290

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During the last 30 years our knowledge and understanding of molecular processes has followed the development of increasingly sophisticated tech niques for studying fast reactions. Although the results are reported in papers and reviews, it is sometimes difficult for those not themselves active in these fields to find their way through the mass of published material. We hope that each book in this series will present a clear account of the present state of knowledge in a particular field of physical chemistry to research workers in related fields, to research students, and for the preparation of undergraduate and post-graduate lectures. Each chapter describes the theoretical develop ment of one area of study and the appropriate experimental techniques; the results presented are chosen to illustrate the theory rather than to attempt a comprehensive review. The first volume published in 1972 was concerned with the reactions of small molecules and free radicals in the gas phase. The development of flash photolysis in the 1950s paved the way by making it possible to generate free radicals in sufficient concentration for a spectroscopic" snapshot" to reveal their molecular structure. Their role in kinetic systems could then be followed directly, rather than be inferred from mechanism. The shock tube enabled gas mixtures to be heated to any desired temperature in a time which was shorter than subsequent chemical reactions. Discharge-flow methods enabled the reactions of atoms and free radicals to be studied directly.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 223

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The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O3 --> ClO + O2 reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mole. The derived product center-of-mass angular and translational energy distributions show that the reaction has a direct reaction mechanism and that there is a strong repulsion on the exit channel. The ClO product is sideways and forward scattered with respect to the Cl atom, and the translational energy release is large. The Cl atom is most likely to attack the terminal oxygen atom of the ozone molecule. The Br + O3 --> ClO + O2 reaction has been studied at five collision energies ranging from 5 kcal/mole to 26 kcal/mole. The derived product center-of-mass angular and translational energy distributions are quite similar to those in the Cl + O3 reaction. The Br + O3 reaction has a direct reaction mechanism similar to that of the Cl + O3 reaction. The electronic structure of the ozone molecule seems to play the central role in determining the reaction mechanism in atomic radical reactions with the ozone molecule. The Cl + NO2 --> ClO + NO reaction has been studied at three collision energies ranging from 10.6 kcal/mole to 22.4 kcal/mole. The center-of-mass angular distribution has some forward-backward symmetry, and the product translational energy release is quite large. The reaction proceeds through a short-lived complex whose lifetime is less than one rotational period. The experimental results seem to show that the Cl atom mainly attacks the oxygen atom instead of the nitrogen atom of the NO2 molecule.

Author: Raphael D. Levine
Publisher: Oxford University Press, USA
ISBN:
Category : Science
Languages : en
Pages : 560

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This is a textbook for advanced undergraduate and graduate courses on kinetics or chemical physics. It deals with the molecular-level mechanism of elementary chemical reactions.

Author: S. Bernasek
Publisher: John Wiley & Sons
ISBN: 9780471185475
Category : Science
Languages : en
Pages : 186

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This is an in-depth monograph covering the topic of energy transfer and reactions on solid surfaces. This topic is of great interest now because of its applications to catalysis and solid-state electronics, including the manufacture of semiconductors, integrated circuits and other solid state devices. Initially it describes what is meant by heterogenous reaction dynamics. Basically, this is the study, on a molecular level, of the elementary dynamics of energy transfer and reactions at surface. The emphasis of the book will be on well characterized solid surfaces. Energy transfer and reactions are broadly defined to include phase transitions in adsorbed layers, diffusion, the absorption process itself, and energy transfer between adsorbate and subtrate, as well as gas-surface energy transfer, catalytic and oxidative type surface reactions.

Author: Ahmed H. Zewail
Publisher: World Scientific
ISBN: 9789810217365
Category : Science
Languages : en
Pages : 622

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These two volumes on Femtochemistry present a timely contribution to a field central to the understanding of the dynamics of the chemical bond. This century has witnessed great strides in time and space resolutions, down to the atomic scale, providing chemists, biologists and physicists with unprecedented opportunities for seeing microscopic structures and dynamics. Femtochemistry is concerned with the time resolution of the most elementary motions of atoms during chemical change -- bond breaking and bond making -- on the femtosecond (10-15 second) time scale. This atomic scale of time resolution has now reached the ultimate for the chemical bond and as Lord George Porter puts it, chemists are near the end of the race against time. These two volumes cover the general concepts, techniques and applications of femtochemistry.Professor Ahmed Zewail, who has made the pioneering contributions in this field, has from over 250 publications selected the articles for this anthology. These volumes begin with a commentary and a historical chronology of the milestones. He then presents a broad perspective of the current state of knowledge in femtochemistry by researchers around the world and discusses possible new directions. In the words of a colleague, "it is a must on the reading-list for all of my students ... all readers will find this to be an informative and valuable overview."The introductory articles in Volume I provide reviews for both the non-experts as well as for experts in the field. This is followed by papers on the basic concepts. For applications, elementary reactions are studied first and then complex reactions. Volume I is complete with studies of solvation dynamics, non-reactive systems, ultrafast electron diffraction and the control of chemical reactions.Volume II continues with reaction rates, the concept of elementary intramolecular vibrational-energy redistribution (IVR) and the phenomena of rotational coherence which has become a powerful tool for the determination of molecular structure via time resolution. The second volume ends with an extensive list of references, according to topics, based on work by Professor Zewail and his group at Caltech.These collected works by Professor Zewail will certainly be indispensable to both experts and beginners in the field. The author is known for his clarity and for his creative and systematic contributions. These volumes will be of interest and should prove useful to chemists, biologists and physicists. As noted by Professor J Manz (Berlin) and Professor A W Castleman, Jr. (Penn State): femtochemistry is yielding exciting new discoveries from analysis to control of chemical reactions, with applications in many domains of chemistry and related fields, e.g., physical, organic and inorganic chemistry, surface science, molecular biology, ... etc.