Download or read book Molecular Beam Studies on Multiphoton Dissociation of Polyatomic Molecules written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A study is made of the multiphoton dissociation of SF6 and other molecules under the collisionless molecular beam conditions used routinely. The results are unambiguously consistent with a far more orderly picture of the excitation and dissociation process than that suggested previously. It is concluded that although the initial excitation is selective, nearly complete energy randomization must take place in the molecular vibrational degrees of freedom before decomposition. 26 references. (JFP).
Download or read book Molecular Beam Studies of IR Laser Induced Multiphoton Dissociation and Vibrational Predissociation written by and published by . This book was released on 1980 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The advancement of crossed molecular beam methods, modern spectroscopy and laser technology allows us to observe chemical reactions on atomic and molecular levels in great detail. After a brief history of crossed molecular beams studies, the author describes and discusses the universal molecular beam apparatus and gives examples of crossed molecular beam studies. The crossed beam technique is compared to other techniques used to provide microscopic information on reaction dynamics. Application of crossed laser and molecular beam studies to the problem of IR multiphoton dissociation of polyatomic molecules is discussed. Study of vibrational predissociation of hydrogen-bonded and van der Waals molecular clusters are discussed. Future cases that the author considers worth pursuing that could benefit from the collisionless environment of molecular beams are enumerated.
Download or read book Multiple Photon Excitation and Dissociation of Polyatomic Molecules written by Cyrus D. Cantrell and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the early 1970s, researchers in Canada, the Soviet Union and the United States discovered that powerful infrared laser pulses are capable of dissociating mole cules such as SiF4 and SF6' This result, which was so unexpected that for some time the phenomenon of multiple-photon dissociation was not recognized in many cir cumstances in which we now know that it occurs, was first publicized at a time when the possibility of using lasers for the separation of isotopes had attracted much attention in the scientific community. From the mid-1970s to the early 1980s, hun dreds of experimental papers were published describing the multiple-photon absorp tion of C02 laser pulses in nearly every simple molecule with an absorption band in the 9 - 11 jJm region. Despite this impressive volume of experimental results, and despite the efforts of numerous theorists, there is no agreement among re searchers in the field on many fundamental aspects of the absorption of infrared laser light by polyatomic molecules. This book is devoted to reviells of the experimental and theoretical research that provides the foundations for our current understanding of molecular multiple photon exc itat i on, and to rev i ews of research that is pert i nent to the 1 aser sep aration of isotopes.
Download or read book Dynamics of Infrared Multiphoton Dissociation of SF6 by Molecular Beam Method Nonrandomize Excitation Energy written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The decomposition of polyatomic molecules by infrared multiphoton absorption is a subject which is under extensive investigation in many laboratories. The process has been shown to be efficient, selective and collisionless. The physical principles which are mainly responsible for the absorption of a large number of photons by an isolated molecule under intense infrared laser radiation have been elucidated through many experimental and theoretical investigations. However, one very important question which remains to be answered is the relation between the dynamics of molecular decomposition and the degree of vibrational excitation, i.e., the question of whether the excitation energy is completely randomized before molecular decomposition. The production of electronically excited fragments in the dissociation of halogenated hydrocarbons and the observations of SF4 fragment in the decomposition of SF6 without the evidence of the formation of lower energy SF5 fragment provided some basis of speculation that the excitation energy might not be randomized before the dissociation of excited molecules. A crossed molecular beam apparatus has been adapted to study the dynamics of excitation and dissociation of polyatomic molecules in intense IR laser fields. Initial experiments have involved the study of the dissociation of SF6 by CO2 laser radiation at 10.6 .mu.m. a molecular beam of SF6 was formed by supersonic expansion using three stages of differential pumping. A grating tuned pulsed CO2 TEA laser was used as the excitation source. The laser beam was focused by a 25 cm focal length ZnSe lens, and crossed the molecular beam near its focal point. The fragments produced by multiphoton dissociation of SF6 within the small interaction region were detected as a function of recoil angle and velocity.
Download or read book Multiphoton Dissociation of Polyatomic Molecules written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamics of infrared multiphoton excitation and dissociation of SF6 was investigated under collision free conditions by a crossed laser-molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments were carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of SF6, the pulse duration of the CO2 laser and the frequency in both one and two laser experiments. Translational energy distributions of the SF5 dissociation product measured by time of flight and angular distributions and the dissociation lifetime of excited SF6 as inferred from the observation of secondary dissociation of SF5 into SF4 and F during the laser pulse suggest that the dynamics of dissociation of excited molecules is dominated by complete energy randomization and rapid intramolecular energy transfer on a nanosecond timescale, and can be adequately described by RRKM theory. An improved phenomenological model including the initial intensity dependent excitation, a rate equation describing the absorption and stimulated emission of single photons, and the unimolecular dissociation of excited molecules is constructed based on available experimental results. The model shows that the energy fluence of the laser determines the excitation of molecules in the quasi-continuum and the excess energy with which molecules dissociate after the laser pulse. The role played by the laser intensity in multiphoton dissociation is more significant than just that of overcoming the intensity dependent absorption in the lowest levels. 63 references.
Download or read book Molecular Beam Photodissociation Studies of Polyatomic Molecules and Radicals written by Eric J. Hintsa and published by . This book was released on 1989 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multiphoton Dissociation of Polyatomic Molecules written by Peter A. Schulz and published by . This book was released on 1979 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proposed Molecular Beam Determination of Energy Partition in the Photodissociation of Polyatomic Molecules written by Richard N. Zare and published by . This book was released on 1964 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book MULTIPHOTON DISSOCIATION PRODUCTS FROM HALOGENATED HYDROCARBONS written by and published by . This book was released on 1977 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent interest in multiphoton dissociation (MPD) of polyatomic molecules has revealed quite a bit of confusion as to what the major dissociation channels of some molecules are, and whether the dissociation process can be described by a statistical, e.g., RRKM, theory of unimolecular reactions. In a gas cell experiment an experimenter often finds great difficulties in answering questions such as: do vibrationally excited molecules react with one another, how do reactions involving free radicals produced in the dissociation proceed, can these radicals decompose further in the presence of the laser field, and does the detection method used actually probe the primary dissociation channel. Using the molecular beam setup previously described, we have overcome most of these difficulties. We have studied MPD of a number of compounds, mainly halogenated methanes, ethanes and ethylenes, and identified their major dissociation channels. To identify an MPD product, we realize that a unique set of ratios between mass spectrometer signals of various ion fragments must first be established for a given molecular species or radical, and preferably the velocity distributions of the dissociation products should be measured and checked for consistency. In our setup, we could measure both angular and time-of-flight distributions for the fragments, and pereorm this check. The low density of molecules in the beam and the extremely low duty cycle in our experiment prevented us from observing the competing minor channels which have very small branching ratios (
Download or read book Energy Research Abstracts written by and published by . This book was released on 1992 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanisms of Multiphoton Dissociation of Molecular Ions written by Michael J. Coggiola and published by . This book was released on 1978 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamics of multiphoton absorption and dissociation of polyatomic ions will be studied to characterize the details of the process. Ion fragments will be identified and the energy released into translation will be measured using a coaxial laser ion beam spectrometer. Single photon absorption studies of positive and negative polyatomic ions failed to reveal any vibrational absorptions in the infrared region investigated. A single photon electronic transition absorption in O2(+) was found which resulted in dissociation. (Author).
Download or read book Multiphoton Processes in Isolated Atoms and Molecules written by Aasmund Sveinung Sudbo and published by . This book was released on 1979 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Beam Studies of Photodissociation Reactions written by Douglas John Krajnovich and published by . This book was released on 1983 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 818 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectroscopy and Dynamics of Multiphoton Processes in Some Selected Small Molecules written by Richard James Stephen Morrison and published by . This book was released on 1982 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Induced Chemical Processes written by Jeffrey I. Steinfeld and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: The possibility of initiating chemical reactions by high-intensity laser exci tation has captured the imagination of chemists and physicists as well as of industrial scientists and the scientifically informed public in general ever since the laser first became available. Initially, great hopes were held that laser-induced chemistry would revolutionize synthetic chemistry, making possible "bond-specific" or "mode-specific" reactions that were impos sible to achieve under thermal equilibrium conditions. Indeed, some of the early work in this area, typically employing high-power continuous-wave sources, was interpreted in just this way. With further investigation, however, a more conservative picture has emerged, with the laser taking its place as one of a number of available methods for initiation of high-energy chemical transformations. Unlike a number of these methods, such as flash photolysis, shock tubes, and electron-beam radiolysis, the laser is capable of a high degree of spatial and molecular localization of deposited energy, which in turn is reflected in such applications as isotope enrichment or localized surface treatments. The use of lasers to initiate chemical processes has led to the discovery of several distinctly new molecular phenomena, foremost among which is that of multiple-photon excitation and dissociation of polyatomic molecules. This research area has received the greatest attention thus far and forms the focus of the present volume.
Download or read book Molecular Beam Studies of Oxygen Atom Reactions with Unsaturated Hydrocarbons written by Annemarie Schmoltner and published by . This book was released on 1989 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt:
