Download or read book State to state Reaction Dynamics of H D2 and the Alignment and Orientation of Hydrogen Molecules written by Nathaniel Chung-Ming Bartlett and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis details part of the ongoing experimental effort on the investigation of the dynamics of the simplest neutral bimolecular reaction system: H + D2 hydrogen exchange. A combination of molecular beam and laser-based spectroscopic techniques have been used to produce H + D2 collisions under single collision conditions, and the three-dimensional velocity distribution of state-selected HD(v', j') reaction products is captured by ion imaging. HBr and D2 are pre-mixed and co-expanded into high vacuum through a pulsed nozzle. The co-expansion produces rotationally cooled reagents with very little relative translational energy between them. The molecular beam is collimated by a skimmer before being intersected with a narrow-linewidth tunable ultraviolet laser pulse which cleaves the HBr bond, producing nearly monoenergetic H atoms which can then react with D2 molecules. Nascent HD(v', j') is state-selectively ionized via resonance-enhanced multiphoton ionization (REMPI) using radiation from another narrow-linewidth tunable ultraviolet laser pulse. This process takes place within the extraction region of a linear time-of-flight mass spectrometer fitted with an imaging detector. This configuration allows the three-dimensional velocity of individual HD(v', j') products to be recorded. Velocity distributions are analyzed and converted into center-of-mass frame scattering angle distributions or differential cross sections (DCS) using photoloc. Using these methods state-to-state differential cross sections have been measured for H + D2(v'=0, j'=0,1,2) --> HD(v'=2, j'=0,3,6,9) + D for collision energies of Ec = 1.25, 1.61, and 1.97 eV. The DCSs are compared to those calculated by Foudhil Bouakline and Stuart Althorpe after being "blurred" according to our experimental conditions. The measured DCSs are in most cases in good agreement with the calculated ones, and show the expected behavior for this reaction system which takes place via a direct recoil mechanism through a collinear transition state geometry. For a given collision energy, as the HD rotational state increases the DCSs shift from being strongly peaked in the backward scattering region to being peaked toward more sideward angles. For a given HD rotational state, as the collision energy increases the DCSs narrow and become peaked at slightly larger angles. The HD(v'=2, j'=0) state produced from reactive collisions at Ec = 1.25 eV displays unique scattering behavior in that its DCS is bimodal. This suggests that there are two competing mechanisms available for this product at this collision energy. The first is the same direct recoil mechanism responsible for product formation of all other rotational state/collision energy combinations investigated. The second is an indirect mechanism opened by a barrier resonance in which the transition state is able to rotate a fraction of a cycle before breaking apart into products. The dynamics observed here are overall similar to that found in related H + D2(v'=0, j'=0,1,2) --> HD(v'=1,3, j') reactive scattering studies performed by our group. Additionally, in a series of adjacent experiments, stimulated Raman pumping (SRP) with polarized light was used to prepare highly aligned and oriented samples of vibrationally-rotationally excited hydrogen molecules in a molecular beam expansion under collision-free conditions. Of particular significance, the (1,0) S(0) SRP line was used to prepare samples of H2(v=1, j=2, M=0) and H2(v=1, j=2, M=2) using linear or circularly polarized light, respectively. After excitation the degree of alignment was monitored using resonance-enhanced multiphoton ionization also with polarized light. This rotational level is not subject to hyperfine depolarization and we find that the samples produced retain their initial degree of alignment or orientation for up to 8 [Mu]s which makes them quite suitable for serving as aligned targets in H + H2 scattering experiments. The same SRP scheme was also used to produce aligned samples of HD(v=1, j=2, M=0) and D2(v=1, j=2, M=0) as well, both of which undergo hyperfine depolarization, through the coupling of the molecules' rotational angular momentum to the nuclear spin angular momenta. The result is that the degree of alignment becomes an oscillatory function of time, which again can be observed using REMPI. We compare the measured time-dependent alignment with a theoretical calculation for HD(v=0, j=2, M=0) and D2(v=0, j=2, M=0) and find the agreement to be within our experimental error. Thus we conclude that the hyperfine constants do not strongly vary with the vibrational state.
Download or read book State to State Dynamical Research in the F H2 Reaction System written by Zefeng Ren and published by Springer Science & Business Media. This book was released on 2013-11-09 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis addresses two important and also challenging issues in the research of chemical reaction dynamics of F+H2 system. One is to probe the reaction resonance and the other is to determine the extent of the breakdown of the Born-Oppenheimer approximation (BOA) experimentally. The author introduces a state-of-the-art crossed molecular beam-scattering apparatus using a hydrogen atom Rydberg "tagging" time-of-flight method, and presents thorough state-to-state experimental studies to address the above issues. The author also describes the observation of the Feshbach resonance in the F+H2 reaction, a precise measurement of the differential cross section in the F+HD reaction, and validation of a new accurate potential energy surface with spectroscopic accuracy. Moreover, the author determines the reactivity ratio between the ground state F(2P3/2) and the excited state F*(2P1/2) in the F+D2 reaction, and exploits the breakdown of BOA in the low collision energy.
Download or read book Encyclopedia of Chemical Physics and Physical Chemistry written by John H. Moore and published by CRC Press. This book was released on 2023-07-03 with total page 1161 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Encyclopedia of Physical Chemistry and Chemical Physics introduces possibly unfamiliar areas, explains important experimental and computational techniques, and describes modern endeavors. The encyclopedia quickly provides the basics, defines the scope of each subdiscipline, and indicates where to go for a more complete and detailed explanation. Particular attention has been paid to symbols and abbreviations to make this a user-friendly encyclopedia. Care has been taken to ensure that the reading level is suitable for the trained chemist or physicist. The encyclopedia is divided in three major sections: FUNDAMENTALS: the mechanics of atoms and molecules and their interactions, the macroscopic and statistical description of systems at equilibrium, and the basic ways of treating reacting systems. The contributions in this section assume a somewhat less sophisticated audience than the two subsequent sections. At least a portion of each article inevitably covers material that might also be found in a modern, undergraduate physical chemistry text. METHODS: the instrumentation and fundamental theory employed in the major spectroscopic techniques, the experimental means for characterizing materials, the instrumentation and basic theory employed in the study of chemical kinetics, and the computational techniques used to predict the static and dynamic properties of materials. APPLICATIONS: specific topics of current interest and intensive research. For the practicing physicist or chemist, this encyclopedia is the place to start when confronted with a new problem or when the techniques of an unfamiliar area might be exploited. For a graduate student in chemistry or physics, the encyclopedia gives a synopsis of the basics and an overview of the range of activities in which physical principles are applied to chemical problems. It will lead any of these groups to the salient points of a new field as rapidly as possible and gives pointers as to where to read about the topic in more detail.
Download or read book Encyclopedia of Chemical Physics and Physical Chemistry Fundamentals written by John H. Moore and published by Taylor & Francis. This book was released on 2001 with total page 1178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book State to state Reaction Dynamics Energy Transfer and Scattering in Collisions of Hydrogen and Deuterium Atoms with Hydrogen Molecules written by Haozhe Dong and published by . This book was released on 1990 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantitative Fundamental Chemical Reaction Dynamics written by Richard Stanley Blake and published by . This book was released on 1988 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advances in Atomic Molecular and Optical Physics written by and published by Elsevier. This book was released on 1994-07-26 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt: The latest volume in the highly acclaimed series addresses atomic collisions, assessing the status of the current knowledge, identifying deficiencies, and exploring ways to improve the quality of cross-section data.Eleven articles, written by foremost experts, focus on cross-section determination by experiment or theory, on needs in selected applications, and on efforts toward the compilation and dissemination of data. This is the first volume edited under the additional direction of Herbert Walther. Presents absolute cross sections for atomic collisions Uses benchmark measurements and benchmark calculations Discusses needs for cross-section data in applications Contains a guide to data resources, bibliographies, and compendia
Download or read book Molecular Rydberg Tagging and Its Application to Chemical Reaction Dynamics written by Hao Xu and published by . This book was released on 1998 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Materials and Molecular Research Division Annual Report written by Lawrence Berkeley Laboratory. Materials and Molecular Research Division and published by . This book was released on 1986 with total page 340 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 2668 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book INIS Atomindex written by and published by . This book was released on 1995 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1420 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Atom Molecule Collision Theory written by Richard Barry Bernstein and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 785 pages. Available in PDF, EPUB and Kindle. Book excerpt: The broad field of molecular collisions is one of considerable current interest, one in which there is a great deal of research activity, both experi mental and theoretical. This is probably because elastic, inelastic, and reactive intermolecular collisions are of central importance in many of the fundamental processes of chemistry and physics. One small area of this field, namely atom-molecule collisions, is now beginning to be "understood" from first principles. Although the more general subject of the collisions of polyatomic molecules is of great im portance and intrinsic interest, it is still too complex from the viewpoint of theoretical understanding. However, for atoms and simple molecules the essential theory is well developed, and computational methods are sufficiently advanced that calculations can now be favorably compared with experimental results. This "coming together" of the subject (and, incidentally, of physicists and chemists !), though still in an early stage, signals that the time is ripe for an appraisal and review of the theoretical basis of atom-molecule collisions. It is especially important for the experimentalist in the field to have a working knowledge of the theory and computational methods required to describe the experimentally observable behavior of the system. By now many of the alternative theoretical approaches and computational procedures have been tested and intercompared. More-or-Iess optimal methods for dealing with each aspect are emerging. In many cases working equations, even schematic algorithms, have been developed, with assumptions and caveats delineated.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1988 with total page 908 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes all works deriving from DOE, other related government-sponsored information and foreign nonnuclear information.
Download or read book Reaction Dynamics written by Justin Jankunas and published by LAP Lambert Academic Publishing. This book was released on 2014-03 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen exchange reaction, H + H, has been studied for over eighty years, yet our understanding of this simplest neutral chemical reaction is incomplete. Research presented in this book are nature's answer to the question, 'Where do products of the H + H reaction scatter with respect to a particular direction in the center-of-mass frame?'. Differential cross sections offer an invaluable insight into the H + H reaction dynamics. Some of the findings follow our intuition, based on classical mechanics, wherein the collision between a hydrogen atom and a hydrogen molecule could be thought of as a type of molecular billiards. Our naive models of the H + H reaction fail, when the product kinetic energy becomes small. Although the experimental results can still be interpreted in the realm of classical mechanics, a better way to think of chemical reactions is to picture a warped billiard table that changes its shape as the molecules approach one another. Geometric phase effects in the H + H system are of a purely quantum mechanical origin. An experimental attempt to capture the 'nuclei at a conical intersection' is presented in the last part of the book.
Download or read book State Resolved Reaction Dynamics written by Richard N. Zare and published by . This book was released on 1985 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past three years major progress has been made in three areas: (1) the study of the simplest of all neutral bimolecular reactions H + D2 yields HD + D using one laser to generate fast H atoms in the photolysis of HI in an HI + D2 mixture and a second laser to detect the HD product in a quantum state specific manner by resonance-enhanced multiphoton ionization of Hd via the E, F I sigma g + state; (2) The determination of the distribution of impact parameters responsible for the formation of BaI(v=8) product in the beam-gas reaction Ba + HI. This required a full rotational analysis of the BaI sq X sigma + and sq C pi states; (3) The commencement of studies on ion-molecule reactions in which the reagent ion's vibrational and translation energy is controlled and varied in a systematic manner.
Download or read book Mass Spectrometry Bulletin written by and published by . This book was released on 1992 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:
